Use a ‘knowledge map’ to rank topics: confident, needs review, weak; focus on weak areas
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Use a ‘knowledge map’ to rank topics: confident, needs review, weak; focus on weak areas
26 subtopics
A perspective is how a particular situation is viewed and understood by an individual. It is based on a mix of personal and collective assumptions, values and beliefs.
Personal perspectives give rise to a wide range of different positions on environmental and social issues. Perspectives also influence people's choices and actions.
Perspectives are informed and justified by sociocultural norms, scientific understandings, laws, religion, economic conditions, local and global events, and lived experience, among other factors.
A perspective is not the same as an argument. Arguments are made to support a personally held perspective or to counter a different one.
Values are qualities or principles that people feel have worth and importance in life.
Values affect people's priorities, judgements, perspectives and choices. They are individual but are shared with, and shaped by, others in a community.
The values that underpin our perspectives can be seen in our communication and actions with the wider community. The values held by organizations can be seen through advertisements, media, policies and actions.
Different values often lead to tensions between individuals and between organizations.
Values surveys can be used to investigate the perspectives shown by a particular social group towards environmental issues.
The effective design of values surveys for a particular social group accommodates various perspectives towards a particular environmental issue, and assesses how these are likely to impact the issue.
Application of skills: Design and carry out questionnaires/surveys/interviews, using online collaborative survey tools, to correlate perspectives with attitudes towards particular environmental or sustainability issues. Select a suitable statistical tool to analyse this data. Students may use and develop behaviour-time graphs to show lifestyle changes.
Worldviews are the lenses shared by groups of people through which they perceive, make sense of and act within their environment. They shape people's values and perspectives through culture, philosophy, ideology, religion and politics.
With the development of the internet and social media, one's perspective can be influenced by a far greater variety of worldviews than just that of the local community. Consequently, models that attempt to classify perspectives, though helpful, are invariably inaccurate as individuals often have a complex mix of positions.
An environmental value system is a model that shows the inputs affecting our perspectives and the outputs resulting from our perspectives.
A value system has inputs (for example, information from media, education, worldviews) and outputs (for example, our judgements, positions, choices and actions).
Environmental perspectives (worldviews) can be classified into the broad categories of technocentric, anthropocentric and ecocentric.
These are not exclusive categories; a variety of alternative schemes exist. There are many ways to classify our perspectives; these models are useful but imperfect, as individuals often have a complex range of positions that change over time and context. Technocentrism assumes all environmental issues can be resolved through technology. Anthropocentrism views humankind as being the central, most important element of existence, and it splits into a wide variety of views. Ecocentrism sees the natural world as having pre-eminent importance and intrinsic value.
Perspectives and the beliefs that underpin them change over time in all societies. They can be influenced by government or non-governmental organization (NGO) campaigns or through social and demographic change.
Application of skills: Interpret behaviour-time graphs. Examples could include specific changes, such as smoking, littering, eating meat or how traditional lifestyles in indigenous cultures are being replaced by modern ones.
The development of the environmental movement has been influenced by individuals, literature, the media, major environmental disasters, international agreements, new technologies and scientific discoveries.
Select one example of influence from each of the following categories.
• An individual environmental activist
• An author
• The media—for example, Al Gore's documentary An Inconvenient Truth (2006), No Impact Man (2009), Breaking Boundaries: The Science of Our Planet (2021)
• An environmental disaster—for example, Minamata disaster (1956), Chernobyl disaster (1986), Fukushima Daiichi nuclear disaster (2011)
• International agreements—for example, Rio Earth Summit (1992) and Rio+20 (2012); 2015 and 2022 United Nations Climate Change Conferences (COP 21, COP 27)
• Technological developments—for example, the Green Revolution, reduction of energy inputs and enteric fermentation, plant-based meats
• Scientific discovery—for example, pesticide and biocide toxicity, species loss, habitat degradation
Examples may also be recent, from indigenous cultures or local/global events of student interest.
Systems are sets of interacting or interdependent components.
System components are organized to create a functional whole.
A systems approach is a holistic way of visualizing a complex set of interactions, and it can be applied to ecological or societal situations.
A system has storages and flows, with flows providing inputs and outputs of energy and matter.
In system diagrams, storages are usually represented as rectangular boxes and flows as arrows, with the direction of each arrow indicating the direction of each flow.
Application of skills: Create systems diagrams representing the storages and flows, inputs and outputs of systems, such as a lab-based or local natural ecosystems. The size of the boxes and the arrows may be representative of the size/magnitude of the storage or flow.
Flows are processes that may be either transfers or transformations.
Transfers involve a change in location of energy or matter; transformations involve a change in the chemical nature, a change in state or a change in energy.
Systems can be open or closed.
An open system exchanges both energy and matter across its boundary, while a closed system exchanges only energy across its boundary. Almost all systems are open; only the global geochemical cycles approximate to closed systems. Biosphere 2 is an example of a closed system, and a local ecosystem is an example of an open system.
The Earth is a single integrated system encompassing the biosphere, the hydrosphere, the geosphere, the cryosphere, the atmosphere and the anthroposphere.
James Lovelock's Gaia hypothesis is a model of the Earth as a single integrated system. The hypothesis (also known as the Gaia theory) was introduced to explain how atmospheric composition and temperatures are interrelated through feedback control mechanisms. Many variations of the Gaia theory were further developed by James Lovelock and Lynn Margulis.
The concept of a system can be applied at a range of scales.
Systems are at a range of scales, including a small-scale local ecosystem, such as a bromeliad in a rainforest; a large ecosystem, such as a rainforest; and the Gaia hypothesis or atmospheric circulation as an example of a global system.
Negative feedback loops occur when the output of a process inhibits or reverses the operation of the same process in such a way as to reduce change. They are stabilizing as they counteract deviation.
Use James Lovelock and Andrew Watson's Daisyworld model to show how temperature regulation can occur due to the presence of life on a planet in contrast with a dead one. Include other examples.
Application of skills: Use diagrams representing examples of negative feedback.
As an open system, an ecosystem will normally exist in a stable equilibrium, either in a steady-state equilibrium or in one developing over time (for example, succession), and will be maintained by stabilizing negative feedback loops.
A stable equilibrium is the condition of a system in which there is a tendency for it to return to the previous equilibrium following disturbance. A steady-state equilibrium is the condition of an open system in which flows are still occurring but inputs are constantly balanced with outputs.
Positive feedback loops occur when a disturbance leads to an amplification of that disturbance, destabilizing the system and driving it away from its equilibrium.
Positive feedback loops have amplifying roles. Positive feedback can lead to both an increase or a decrease in a system component. For example, as a population declines, the reproductive potential decreases leading to further decrease. An example of positive feedback is the reduced albedo (amount of reflection by a surface) due to melting ice caps leading to greater global warming, or an increase in population leading to increased potential for further growth. There are many other examples.
Application of skills: Use diagrams representing examples of positive feedback.
Positive feedback loops will tend to drive the system towards a tipping point.
A tipping point is the minimum amount of change that will cause destabilization within a system. The system then shifts to a new equilibrium or stable state.
Tipping points can exist within a system where a small alteration in one component can produce large overall changes, resulting in a shift in equilibrium.
Tipping points result in regime shifts between alternative stable states.
Use examples to support the explanation. For example, a change of nitrate/phosphate concentrations leading to eutrophication.
Identify other examples of such tipping points throughout the course.
A model is a simplified representation of reality; it can be used to understand how a system works and to predict how it will respond to change.
A model may take many forms, including a graph, a diagram, an equation, a simulation or words. Models are used throughout the course to represent systems and processes.
Simplification of a model involves approximation and, therefore, loss of accuracy.
The simplification of a model can make it less accurate. The systems approach uses models throughout the course. For example, predictive models of climate change or projections of human population growth explain how a model may give very different results. Simplification will also affect how well a lab-based model ecosystem approximates to a natural ecosystem.
Interactions between components in systems can generate emergent properties.
Emergent properties appear as individual system components interact; the components themselves do not have these properties. For example, predator–prey oscillations and trophic cascades are examples of emergent properties where patterns of change occur that would not occur in isolated components. Include other examples.
The resilience of a system, ecological or social, refers to its tendency to avoid tipping points and maintain stability.
Resilience of a system is the capacity to resist damage and recover from, or adapt efficiently to, disturbance.
Diversity and the size of storages within systems can contribute to their resilience and affect their speed of response to change (time lags).
Consider an example of resilience (for example, the loss of resilience with the displacement of North American prairie systems with monoculture crops) showing how diversity contributes to the resilience of a system. Consider how size of storage affects the relative stability of a puddle compared to a lake.
Humans can affect the resilience of systems through reducing these storages and diversity.
Use the example of loss of resilience in deforestation resulting in reduced size of storages and loss of diversity.
Sustainability is a measure of the extent to which practices allow for the long-term viability of a system. It is generally used to refer to the responsible maintenance of socio-ecological systems such that there is no diminishment of conditions for future generations.
All activity is embedded in a system and, in general, enhancing system resilience increases sustainability.
Sustainability is comprised of environmental, social and economic pillars.
The ways in which environmental, social and economic sustainability interact can be shown with diagrams. Strong sustainability models show the economy embedded in society, and both society and economy embedded in the natural environment. Weak sustainability models only show an overlap in the three pillars.
Environmental sustainability is the use and management of natural resources that allows replacement of the resources, and recovery and regeneration of ecosystems.
Sustainability in this context focuses on resource depletion, pollution and conserving biodiversity. Active regeneration of ecosystems is also considered a component of environmental sustainability. There are different timescales in the replacement of natural resources.
Social sustainability focuses on creating the structures and systems, such as health, education, equity, community, that support human well-being.
Sustainability in this context focuses on the survival of societies and their cultures; it may include consideration of the continued use of language, belief, or spiritual practices in a society.
Economic sustainability focuses on creating the economic structures and systems to support production and consumption of goods and services that will support human needs into the future.
In terms of resource use to meet human needs, there is no economic sustainability without environmental sustainability.
Sustainable development meets the needs of the present without compromising the ability of future generations to meet their own needs. Sustainable development applies the concept of sustainability to our social and economic development.
Sustainable development is a framework that guides further development of human civilization while maintaining economic stability, social equity and ecological integrity. The Brundtland report of 1987 introduced the social and economic aspects of sustainability to sustainable development.
Unsustainable use of natural resources can lead to ecosystem collapse.
Use an example of ecosystem collapse due to human overexploitation of the environment (for example, the impact of overfishing on Newfoundland cod fisheries).
Common indicators of economic development, such as gross domestic product (GDP), neglect the value of natural systems and may lead to unsustainable development.
GDP is a measure of the monetary value of final goods and services produced and sold in a given period by a country. Focusing on GDP as a measure of economic progress may cause unsustainable development.
Green GDP measures environmental costs and subtracts these from GDP.
Environmental justice refers to the right of all people to live in a pollution-free environment, and to have equitable access to natural resources, regardless of issues such as race, gender, socio-economic status, nationality.
Consider one local and one global example of environmental injustice. Examples could include: Deepwater Horizon oil spill, Gulf of Mexico (2010); landfills located in low-income areas; Union Carbide gas release in Bhopal, India (1984); Maasai land rights in Kenya and Tanzania; plastic waste disposal by developed to developing countries.
Inequalities in income, race, gender and cultural identity within and between different societies lead to disparities in access to water, food and energy.
Examples of inequality include the inability to afford an electricity supply, or the privatization of water sources.
Sustainability and environmental justice can be applied at the individual to the global operating scale.
Sustainability and environmental justice issues exist at different operating scales. Different operating scales are individual (individual decisions on how to live and work), business, community (religious, cultural, political, indigenous), city, country (policies, laws and socio-economic systems) or global (for example, the United Nations (UN) Sustainable Development Goals (SDGs)).
Sustainability indicators include quantitative measures of biodiversity, pollution, human population, climate change, material and carbon footprints, and others. These indicators can be applied on a range of scales, from local to global.
Consider the use of one named environmental indicator to assess sustainability.
The concept of ecological footprints can be used to measure sustainability. If these footprints are greater than the area or resources available to the population, this indicates unsustainability.
An ecological footprint is the area of land and water required to sustainably provide all resources at the rate of consumption and absorb all generated waste at the rate of production for a specific population.
Application of skills: Use footprint calculators to establish students' own ecological/carbon/water footprint. Present comparative data on footprints graphically, using a spreadsheet and graph-plotting software.
The carbon footprint measures the amount of greenhouse gases (GHGs) produced, measured in carbon dioxide equivalents (in tonnes). The water footprint measures water use (in cubic metres per year).
There are different ways of using footprints to measure sustainability. Students do not need to know details of how these are calculated.
Biocapacity is the capacity of a given biologically productive area to generate an ongoing supply of renewable resources and to absorb its resulting wastes.
Unsustainability occurs if the area's ecological footprint exceeds its biocapacity.
Citizen science plays a role in monitoring Earth systems and whether resources are being used sustainably.
Citizen science has a role in the larger picture of scientific research on environmental systems. The information gathered is relevant to local problems and conditions, and can be used in research on global issues, such as climate change.
There are a range of frameworks and models that support our understanding of sustainability, each with uses and limitations.
Sustainability models, like all models, are simplified versions of reality; therefore, they have both uses and limitations.
The UN Sustainable Development Goals (SDGs) are a set of social and environmental goals and targets to guide action on sustainability and environmental justice.
Consider the SDG model and the uses and limitations of the SDGs.
The SDGs provide a framework for sustainable development supported by the UN and address the global challenges faced by humanity, including those related to poverty, inequality, climate, environmental degradation, prosperity, and peace and justice.
Example uses and limitations include the following.
Uses: Setting of a common ground for policymaking; relating to both developed and developing countries; galvanizing the international community into addressing economic and social inequality.
Limitations: Goals not going far enough; goals being top down and bureaucratic; tending to ignore local contexts; lacking in supportive data.
The planetary boundaries model describes the nine processes and systems that have regulated the stability and resilience of the Earth system in the Holocene epoch. The model also identifies the limits of human disturbance to those systems, and proposes that crossing those limits increases the risk of abrupt and irreversible changes to Earth systems.
Consider the planetary boundaries model and select which planetary boundaries appear to have been crossed and factors that have led to this. (HL only: Use quantitative data to discover when, and if, planetary boundaries have been crossed where appropriate in the course.)
Example uses and limitations include the following.
Uses: Identifies science-based limits to human disturbance of Earth systems; highlights the need to focus on more than climate change (which dominates discussion); alerts the public and policymakers about the urgent need for action to protect Earth systems.
Limitations: Focuses only on ecological systems and does not consider the human dimension necessary to take action for environmental justice; the model is a work in progress—assessments of boundaries are changing as new data becomes available; the focus on global boundaries may not be a useful guide for local and country-level action.
The doughnut economics model is a framework for creating a regenerative and distributive economy in order to meet the needs of all people within the means of the planet.
Consider the doughnut economics model and the concepts of regenerative and distributive design.
The social foundation (inner boundary of the doughnut) is based on the social SDGs. The ecological ceiling (outer boundary of the doughnut) is based on planetary boundaries science. Together, the social foundation and the ecological ceiling represent the minimum conditions for an economy that is ecologically safe and socially just—thus, the doughnut is the “safe and just space for humanity”. Today, billions of people still fall short of the social foundation, while humanity has collectively overshot most of the planetary boundaries. Therefore, the goal as illustrated by this model is to move into the doughnut and create an economy that enables humanity to thrive in balance with the rest of the living world. It can only be achieved by making economies that become regenerative and distributive by design. A regenerative economy works with, and within, the cycles and limits of the living world. A distributive economy shares value and opportunity far more equitably among all stakeholders.
Example uses and limitations include the following.
Uses: The model includes both ecological and social elements, so it supports the concept of environmental justice; it has reached popular awareness and is being used at different scales (for example, countries, cities, neighbourhoods, businesses) to support action on sustainability.
Limitations: The model is a work in progress—different groups are trying to apply the model for concrete action; it advocates broad principles of regenerative and distributive practice but does not propose specific policies.
The circular economy is a model that promotes decoupling economic activity from the consumption of finite resources. It has three principles: eliminating waste and pollution, circulating products and materials, and regenerating nature.
The butterfly diagram from the Ellen MacArthur Foundation is a useful illustration of the circular economy. It is different to the linear economic model (take–make–waste).
Example uses and limitations include the following.
Uses: Regeneration of natural systems; reduction of greenhouse gas emissions; improvement of local food networks and support of local communities; reduction of waste by extending product life cycle; changed consumer habits.
Limitations: Lack of environmental awareness by consumers and companies; lack of regulations enforcing recycling of products; some waste is not recyclable—technical limitations; lack of finance.
55 subtopics
The biosphere is an ecological system composed of individuals, populations, communities, ecosystems.
A biosphere represents the parts of the Earth where life exists.
An individual organism is a member of a species.
According to the biological species concept, a species is a group of organisms that can interbreed and produce fertile offspring.
Classification of organisms allows for efficient identification and prediction of characteristics.
Classification is needed because of the immense diversity of species. The first name is the genus, the second name is the species; species in the same genus have similar traits. The genus name is given an initial capital letter. The species name is lower case; both genus and species should be either italicized or underlined.
Taxonomists use a variety of tools to identify an organism.
Identification in this context means determining the species of an individual organism. Tools include dichotomous keys, comparison of specimens with reference to collections by taxonomists, and deoxyribonucleic acid (DNA) surveys.
Application of skills: Know how to use dichotomous keys, applications and databases for the identification of species.
A population is a group of organisms of the same species living in the same area at the same time, and which are capable of interbreeding.
A population is an interbreeding unit. One species may consist of any number of populations, from one to many. The term "metapopulation" is not required.
Application of skills: Investigate a local ecosystem.
Factors that determine the distribution of a population can be abiotic or biotic.
Biotic refers to the living components of an ecosystem; abiotic refers to non-living physical factors that may influence organisms.
Temperature, sunlight, pH, salinity, dissolved oxygen and soil texture are examples of many abiotic factors that affect species distributions in ecosystems.
Abiotic factors can be quantified in order to clarify the distribution of species.
Application of skills: Use methods for measuring at least three abiotic factors in an aquatic or terrestrial ecosystem, including the use of data logging.
A niche describes the particular set of abiotic and biotic conditions and resources upon which an organism or a population depends.
An ecological niche is the role of a species in an ecosystem. The niche comprises all biotic and abiotic interactions that influence the growth, survival and reproduction of a population, including how food is obtained.
Include some of the parameters of a niche for a named species.
Populations interact in ecosystems by herbivory, predation, parasitism, mutualism, disease and competition, with ecological, behavioural and evolutionary consequences.
Consider one example of each relationship and consider how the relationships influence the population dynamics of the interacting populations and the selective pressures involved.
Application of skills: Use models that demonstrate feeding relationships, such as predator–prey.
Carrying capacity is the maximum size of a population determined by competition for limited resources.
Include examples of resources that may affect carrying capacity, including biotic and abiotic factors.
Population size is regulated by density-dependent factors and negative feedback mechanisms.
Density-independent factors may have significant influence on population size, but it is the density-dependent factors that tend to regulate the population around the carrying capacity. In addition to competition for limited resources, include the increased risk of predation and the transfer of pathogens in dense populations. These are examples of negative feedback returning a population to equilibrium.
Population growth can either be exponential or limited by carrying capacity.
If there are no limiting factors, population growth follows a J-curve (exponential growth). When density-dependent limiting factors start to operate, the curve becomes S-shaped. Consider population growth curves in terms of numbers of individuals and rates of change, and populations showing an S-curve and a "boom and bust" pattern, for example, reindeer on St Matthew Island.
Limiting factors on the growth of human populations have increasingly been eliminated, resulting in consequences for sustainability of ecosystems.
Include the effects of elimination of natural predators, technological advances, and degradation of the environment.
Carrying capacity cannot be easily assessed for human populations.
This is because of the broad and changing ecological niche of humans. Include the idea of populations achieving equilibrium within ecosystems, but human populations being less limited due to mobility of resources. The expansion of the human niche also takes place through technological advances and changes in consumption. The rapidly changing human habitat leads to estimates of carrying capacity that are disputed and that can only be estimated for "now".
Population abundance can be estimated using random sampling, systematic sampling or transect sampling.
Consider reasons for selecting which of these procedures would be most appropriate.
Random quadrat sampling can be used to estimate population size for non-mobile organisms.
Percentage cover is an estimate of the area in a given frame size (quadrat) covered by the plant or animal in question. Percentage frequency is the number of occurrences divided by the number of possible occurrences. For example, if a plant occurs in 5 out of 100 squares in a grid quadrat, then the percentage frequency is 5%. Percentage cover and frequency give an estimate of abundance but not actual population size.
Application of skills: Use quadrat sampling estimates for abundance, population density, percentage cover and percentage frequency for non-mobile organisms and measures change along a transect.
Capture–mark–release–recapture and the Lincoln index can be used to estimate population size for mobile organisms.
Consider use of the Lincoln index in estimating population size.
Population size estimate = , where M is the number of individuals caught and marked initially, N is the total number of individuals recaptured and R is the number of marked individuals recaptured.
Application of skills: Students should use the Lincoln index to estimate population size. Students should understand the assumptions made when using this method.
A community is a collection of interacting populations within the ecosystem.
Communities comprise several populations that interact in the ecosystem. Consider the concept of community in a local ecosystem.
Habitat is the location in which a community, species, population or organism lives.
A description of the habitat of a species can include both geographical and physical locations, as well as the type of ecosystem required to meet all environmental conditions needed for survival. Consider the concept of habitat in a local ecosystem.
Ecosystems are open systems in which both energy and matter can enter and exit.
An ecosystem is a community and the physical environment with which it interacts. Consider the concept of ecosystem in a local ecosystem.
Sustainability is a natural property of ecosystems.
Inputs are balanced by outputs in a steady-state ecosystem. Consider this balance in flow diagrams of specific ecosystems. There is evidence for some ecosystems persisting for millions of years, for example, tropical rainforests.
Human activity can lead to tipping points in ecosystem stability.
Tipping points lead to the collapse of the original ecosystem and development of a new equilibrium. For example, deforestation of the Amazon rainforest reduces generation of water vapour through transpiration, and consequently reduces cooling and precipitation necessary for the maintenance of the remaining forest.
Keystone species have a role in the sustainability of ecosystems.
There is a disproportionate impact on community structure of keystone species and the risk of ecosystem collapse if they are removed. Consider two examples. For example, purple sea stars controlling mussel populations on the North Pacific coast that would otherwise overwhelm the ecosystem; elephants feeding on shrubs and trees, and thus maintaining savannah grasslands.
The planetary boundaries model indicates that changes to biosphere integrity have passed a critical threshold.
There is an interrelationship between ecosystems and species diversity. Disturbance of ecosystems due to human activity has led to loss of biosphere integrity. Extinction rates provide evidence that the planetary boundary for biosphere integrity has been crossed.
To avoid critical tipping points, loss of biosphere integrity needs to be reversed.
Ecosystem damage and loss of species can be slowed by protecting the integrity of ecosystems. Protecting ecosystems ensures the preservation of the niche requirements essential for the ongoing survival of a species.
There are advantages of using a method of classification that illustrates evolutionary relationships in a clade.
A clade illustrates evolutionary relationships in which all the members of a taxonomic group have evolved from a common ancestor.
There are difficulties in classifying organisms into the traditional hierarchy of taxa.
The traditional hierarchy of kingdom, phylum, class, order, family, genus and species does not always correspond with patterns of divergence generated by evolution.
The niche of a species can be defined as fundamental or realized.
The fundamental niche describes the range of conditions and resources in which a species could survive and reproduce if there were no limiting factors. The realized niche of a species is the actual mode of existence, which results from its adaptations and competition with other species. Consider the fundamental and realized niche of a named species, such as Joseph Connell's study of barnacle species, or brown and green anoles.
Life cycles vary between species in reproductive behaviour and lifespan.
r- and K-strategists are adapted by their life cycles to different environments and successional stages. K-strategists thrive in stable communities by producing few offspring that have a high chance of survival. r-strategists colonize new habitats rapidly and make opportunistic use of short-lived resources by producing many offspring with more limited provision for the individual's survival.
Knowledge of species' classifications, niche requirements and life cycles help us to understand the extent of human impacts upon them.
Include examples of human impact on life cycles, such as temperature changes from climate change that affect the life cycles of plants, which in turn affect the life cycle of animals.
The life cycles of many species are synchronized with those of others and the seasons. Human impacts are contributing to climate change, which lead to a disruption in these cycles.
Ecosystems are sustained by supplies of energy and matter.
Ecosystems are open systems in which energy and matter are exchanged.
The first law of thermodynamics states that as energy flows through ecosystems, it can be transformed from one form to another but cannot be created or destroyed.
Energy transformations occur, such as light to chemical and from chemical to heat.
Photosynthesis and cellular respiration transform energy and matter in ecosystems.
Transformation of energy is a change from one form to another, such as light to heat. Transformation of matter happens in chemical reactions and can be summarized using word equations.
Application of skills: Create system diagrams from a set of data of ecosystems showing transfers and transformations of energy and matter.
Photosynthesis is the conversion of light energy to chemical energy in the form of glucose, some of which can be stored as biomass by autotrophs.
Glucose can be converted into other carbon compounds contained within biomass. Students are not required to know the biochemical details of photosynthesis.
Producers form the first trophic level in a food chain.
Producers are typically plants, algae and photosynthetic bacteria that produce their own food using photosynthesis.
Cellular respiration releases energy from glucose by converting it into a chemical form that can easily be used in carrying out active processes within living cells.
Students are not required to know that adenosine triphosphate (ATP) is the readily usable energy currency of cells.
Some of the chemical energy released during cellular respiration is transformed into heat.
Heat is generated by cellular respiration because it is not 100% efficient at transferring energy from substrates, such as carbohydrates, into the chemical form of energy used in cells. Heat generated within an individual organism cannot be transformed back into chemical energy and is ultimately lost from the body.
The second law of thermodynamics states that energy transformations in ecosystems are inefficient.
The second law of thermodynamics relates to the quality of energy, and that when energy is transformed, some must be degraded into a less useful form, such as heat. In ecosystems, the biggest losses occur during cellular respiration. The second law of thermodynamics explains why energy transfers are never 100% efficient.
Consumers gain chemical energy from carbon (organic) compounds obtained from other organisms. Consumers have diverse strategies for obtaining energy-containing carbon compounds.
Include, with examples, herbivores, detritivores, predators, parasites, saprotrophs, scavengers and decomposers.
Because producers in ecosystems make their own carbon compounds by photosynthesis, they are at the start of food chains. Consumers obtain carbon compounds from producers or other consumers, so form the subsequent trophic levels.
In a food chain, organic matter flows from primary producers to primary consumers to secondary consumers, and so on.
Application of skills: Create a food chain from given data.
Carbon compounds and the energy they contain are passed from one organism to the next in a food chain. The stages in a food chain are called trophic levels.
Traditionally, decomposers are not included in food chains as they typically gain carbon compounds from a variety of sources. However, consider the role of decomposers in energy transformations in food webs.
There are losses of energy and organic matter as food is transferred along a food chain.
Not all the food available to a given trophic level is harvested: of what is harvested, not all is consumed; of what is consumed, not all is absorbed; of what is absorbed, not all is stored—some is lost as heat through cellular respiration. There is, therefore, never 100% transference of organic matter from one trophic level to the next.
Gross productivity (GP) is the total gain in biomass by an organism. Net productivity (NP) is the amount remaining after losses due to cellular respiration.
Consider values of both GP and NP from given data. Losses due to cellular respiration are typically greater in consumers than in producers due to more energy-requiring activity. The NP of any organism or trophic level is the maximum sustainable yield that can be harvested without diminishing the availability for the future.
The number of trophic levels in ecosystems is limited due to energy losses.
Energy released by cellular respiration and lost as heat by organisms is unavailable to organisms in higher trophic levels. Because of this and other energy losses, typically 10% or less of the energy flowing to a trophic level is available to the next level, limiting the length of food chains. Avoid the common misconception that organisms at higher trophic levels must eat more food to get enough energy.
Application of skills: Work out the efficiency of transfer between trophic levels.
Food webs show the complexity of trophic relationships in communities.
Arrows in food chains and food webs indicate the direction of energy flow and transfer of biomass. In a food web, species may feed at more than one trophic level.
Application of skills: Create a food web from given data.
Biomass of a trophic level can be measured by collecting and drying samples.
Dry mass of samples is approximately equal to mass of organic matter (biomass) since water represents the majority of inorganic matter in most organisms.
Energy in biomass can be measured by combustion of samples and extrapolation.
Ecological pyramids are used to represent relative numbers, biomass or energy of trophic levels in an ecosystem.
Pyramids of number and biomass show the standing crop per unit area at a particular time. Pyramids of energy ("pyramids of productivity" in some texts) show the amount of energy flowing to each trophic level per unit area and per unit time (usually kJ m⁻² year⁻¹). Consider pyramid diagrams and reasons for variations in their shape.
Application of skills: Create pyramids of numbers, biomass and energy from given data.
Follow experimental procedures on how to find biomass and energy from biological samples (plant material only).
Pollutants that are non-biodegradable, such as polychlorinated biphenyl (PCB), dichlorodiphenyltrichloroethane (DDT) and mercury, cause changes to ecosystems through the processes of bioaccumulation and biomagnification.
Bioaccumulation refers to the increasing concentration of non-biodegradable pollutants in organisms or trophic levels over time (as more are absorbed). Biomagnification refers to the increasing concentration of non-biodegradable pollutants along a food chain (due to the loss of biodegradable biomass through, for example, cellular respiration).
Non-biodegradable pollutants are absorbed into the surfaces of microplastics, which increases their transmission in the food chain.
Include an example of pollution by microplastics and its effect on the food chain.
Human activities, such as burning fossil fuels, deforestation, urbanization and agriculture, have impacts on flows of energy and transfers of matter in ecosystems.
Although burning fossil fuels may lead to increased CO2 available for photosynthesis, the other pollutants and impacts of global warming will reduce primary productivity.
Deforestation, urbanization and agriculture all lead to loss of ecosystem biomass, disruption of food webs, and the capacity for photosynthesis.
Autotrophs synthesize carbon compounds from inorganic sources of carbon and other elements. Heterotrophs obtain carbon compounds from other organisms.
All living organisms can be classified as autotrophs or heterotrophs.
Photoautotrophs use light as an external energy source in photosynthesis. Chemoautotrophs use exothermic inorganic chemical reactions as an external energy source in chemosynthesis.
Chemoautotrophs exist in a variety of ecosystems, especially those where there is little or no light. In such ecosystems, chemoautotrophs are the principal source of energy to sustain food webs.
Primary productivity is the rate of production of biomass using an external energy source and inorganic sources of carbon and other elements.
The units usually used for productivity are kg carbon m⁻² year⁻¹ (kilograms of carbon per square metre of ecosystem per year). Consider protocols for determining primary productivity in ecosystems. Estimates can be based on photosynthesizing samples within a laboratory or, in the field, measuring change in biomass of samples (such as grassland) over time.
Secondary productivity is the gain in biomass by consumers using carbon compounds absorbed and assimilated from ingested food.
Secondary productivity is ingested food minus faecal waste. The units are the same as those for primary productivity. Faecal matter is not included as it is material that has remained undigested and unabsorbed.
Net primary productivity is the basis for food chains because it is the quantity of carbon compounds sustainably available to primary consumers.
Net primary production can be thought of as the plant growth that is sustainably harvestable by primary consumers in natural ecosystems or by farmers and foresters in agricultural and silvicultural systems.
Application of skills: Use laboratory and field techniques for measuring primary and secondary productivity and work out GP and NP from data.
Maximum sustainable yields (MSYs) are the net primary or net secondary productivity of a system.
Consider the MSYs in natural ecosystems and in agricultural or silvicultural systems.
Sustainable yields are higher for lower trophic levels.
Include the reasons for sustainability in food production being easier to achieve if humans consume organisms from lower trophic levels, especially plant-based foods.
Ecological efficiency is the percentage of energy received by one trophic level that is passed on to the next level.
The percentage varies between ecosystems, trophic levels and species. Work out the efficiency of the transfer of energy between trophic levels with given data. The percentage of energy transferred from one trophic level to the next is very variable, and the value of 10% is neither a fixed amount nor a true average.
The second law of thermodynamics shows how the entropy of a system increases as biomass passes through ecosystems.
Entropy refers to the amount of disorder within a system. Living systems are able to maintain a high degree of organization and low entropy through the net increase in entropy resulting largely from cellular respiration.
Biogeochemical cycles ensure chemical elements continue to be available to living organisms.
Human impact on these cycles can affect the sustainability of ecosystems.
Biogeochemical cycles have stores, sinks and sources.
Stores (storages) remain in equilibrium with the environment; sinks indicate net accumulation of the element; sources indicate net release of the element.
Organisms, crude oil and natural gas contain organic stores of carbon. Inorganic stores can be found in the atmosphere, soils and oceans.
A store is in equilibrium when absorption is balanced by release. Residence time is the average period that a carbon atom remains in a store. Without human interference (that is, mining) the residence time in fossil fuels would be measured in hundreds of millions of years.
Carbon flows between stores in ecosystems by photosynthesis, feeding, defecation, cellular respiration, death and decomposition.
Consider systems diagrams of the carbon cycle and the difference between transfers and transformations in these flows.
Application of skills: Create a systems diagram of the carbon cycle.
Carbon sequestration is the process of capturing gaseous and atmospheric carbon dioxide and storing it in a solid or liquid form.
Trees sequester carbon naturally by absorbing carbon dioxide and converting it into biomass. Organic matter is fossilized into coal, oil and natural gas.
Ecosystems can act as stores, sinks or sources of carbon.
In an ecosystem, the difference between total inputs and outputs is the net accumulation or release of carbon. If photosynthesis exceeds cellular respiration in an ecosystem there is a net uptake of carbon dioxide, and if cellular respiration exceeds photosynthesis there is a net release of carbon dioxide. Use the example of a young forest acting as a sink, a mature forest acting as a store and a forest that is destroyed by fire or deforestation acting as a source.
Fossil fuels are stores of carbon with unlimited residence times. They were formed when ecosystems acted as carbon sinks in past eras and become carbon sources when burned.
Consider the concept of fossil fuels but not the detail of how and when coal, oil and natural gas were formed.
Agricultural systems can act as carbon stores, sources and sinks, depending on the techniques used.
Some agricultural methods, such as crop rotation, cover crops and no till, will promote the role of soil as a carbon sink whereas drainage of wetland, monoculture and heavy tillage will promote the role of soil as a carbon source. Cropping over a longer timescale (for example, timber production) and the subsequent use of harvested products will also affect these roles.
Carbon dioxide is absorbed into the oceans by dissolving and is released as a gas when it comes out of a solution.
While oceans act as a carbon sink, the human use of fossil fuels releases inorganic carbon at a faster rate than oceans can absorb it.
Increases in concentrations of dissolved carbon dioxide cause ocean acidification, harming marine animals.
Small decreases in pH can interfere with calcium carbonate deposition in mollusc shells and coral skeletons.
Measures are required to alleviate the effects of human activities on the carbon cycle.
Consider at last three of the measures that are required. These include low-carbon technologies, reduction in fossil-fuel burning/soil disruption/deforestation, carbon capture through reforestation and artificial sequestration.
The lithosphere contains carbon stores in fossil fuels and in rocks, such as limestone, that contain calcium carbonate.
The residence time for carbon in these stores can be hundreds of millions of years.
Reef-building corals and molluscs have hard parts that contain calcium carbonate that can become fossilized in limestone.
Limestone is the largest store of carbon in Earth systems. Not all limestone is formed by fossilization of animal remains; it can also be formed by both biological and non-biological processes. Details of these processes are not required.
In past geological eras, organic matter from partially decomposed plants became fossilized in coal, and partially decomposed marine organisms became fossilized in oil and natural gas held in porous rocks.
Formation of coal, oil and gas was greatest in specific geological eras when conditions were most suitable, and it took tens of millions of years for significant stores to accumulate.
Methane is produced from dead organic matter in anaerobic conditions by methanogenic bacteria.
Anaerobic conditions suitable for methanogenesis occur in swamps, rice paddies and the stomachs of cattle and other ruminants.
Methane has a residence time of about 10 years in the atmosphere and is eventually oxidized to carbon dioxide.
Methane is a potent greenhouse gas.
The nitrogen cycle contains organic and inorganic stores.
Organic nitrogen stores in ecosystems consist of proteins and other nitrogenous carbon compounds in living organisms and in dead organic matter. Inorganic stores consist of nitrogen in the atmosphere, as well as ammonia and other nitrogen compounds (nitrites and nitrates) in soil and water.
Application of skills: Create a systems diagram of the nitrogen cycle.
Bacteria have essential roles in the nitrogen cycle.
Nitrogen fixation is conversion of nitrogen from the atmosphere into ammonia; nitrification is conversion of ammonia to nitrates; denitrification is conversion of nitrates to nitrogen; decomposition is the conversion of amino acids into ammonium.
Conversion of ammonium and nitrites to nitrates takes place. Chemical details of reactions are not required.
Denitrification only happens in anaerobic conditions, such as soils that are waterlogged.
In waterlogged, anaerobic soils, plant growth is reduced or stopped and denitrification and leaching take place. In these soils, insectivorous plants (for example, pitcher plants and sundews) can capture and digest insects and use them as a nitrogen source.
Plants cannot fix nitrogen so atmospheric dinitrogen is unavailable to them unless they form mutualistic associations with nitrogen-fixing bacteria.
Include examples of plants that do form such mutualistic associations and the competitive advantage gained by such plants in ecosystems where nitrogen is a limiting factor on plant growth.
Flows in the nitrogen cycle include mineral uptake by producers, consumption, excretion, death, decomposition and ammonification.
Consider systems diagrams of the nitrogen cycle and the difference between transformation (decomposition and ammonification) and transfer flows.
Human activities such as deforestation, agriculture, aquaculture and urbanization change the nitrogen cycle.
Include examples of the changes to the nitrogen cycle caused by these activities.
The Haber process is an industrial process that produces ammonia from nitrogen and hydrogen for use as fertilizer.
Include the advantages and disadvantages of using the Haber process to provide fertilizer for increased crop yield.
Increases in nitrates in the biosphere from human activities have led to the planetary boundary for the nitrogen cycle being crossed, making irreversible changes to Earth systems likely.
Consider the evidence that the boundary for the biogeochemical cycles of nitrogen has been crossed and that global dependence on inorganic fertilizers for crop production is the major cause of this.
Global collaboration is needed to address the uncontrolled use of nitrogen in industrial and agricultural processes and bring the nitrogen cycle back within planetary boundaries.
Consider the measures that are needed to bring the biogeochemical cycles of nitrogen back within planetary boundaries.
Climate describes atmospheric conditions over relatively long periods of time, whereas weather describes the conditions in the atmosphere over a short period of time.
Weather refers to the specific conditions being experienced at a particular time or over a short period, including temperature, humidity, air pressure and wind speed. Climate is the average of these conditions over approximately 30 years.
A biome is a group of comparable ecosystems that have developed in similar climatic conditions, wherever they occur.
Ecosystems developed in similar conditions in different parts of the world can have many parallel features. Precipitation, temperature and insolation are major influences on the distribution of terrestrial biomes.
Abiotic factors are the determinants of terrestrial biome distribution.
For any given temperature and rainfall pattern, one natural ecosystem type is likely to develop. Consider a graph showing the distribution of biomes with temperature and rainfall pattern on the horizontal and vertical axes.
Application of skills: Create climate graphs showing annual precipitation/average temperature for different biomes.
Biomes can be categorized into groups that include freshwater, marine, forest, grassland, desert and tundra. Each of these groups has characteristic abiotic limiting factors, productivity and diversity. They may be further classed into many subcategories (for example, temperate forests, tropical rainforests and boreal forests).
Include the characteristic limiting factors, productivity and resulting biodiversity of tropical rainforests, hot deserts, tundra and at least two other biomes.
The tricellular model of atmospheric circulation explains the behaviour of atmospheric systems and the distribution of precipitation and temperature at different latitudes. It also explains how these factors influence the structure and relative productivity of different terrestrial biomes.
Latitude is the angular distance from the equator (north or south of it) as measured from the centre of the Earth (usually in degrees). Give details of the tricellular model with the three distinct cells: the Hadley cell, the Ferrel cell and the polar cell. Include reasons for the distribution of biomes using the tricellular model.
Application of skills: Use the tricellular model of atmospheric circulation and link it to the planetary distribution of heat and biomes.
The oceans absorb solar radiation and ocean currents distribute the resulting heat around the world.
Details of the great ocean conveyor belt and thermohaline circulation are HL only.
Global warming is leading to changing climates and shifts in biomes.
The general trend is of biomes moving poleward and to higher altitude.
There are three general patterns of climate types that are connected to biome types.
Climate types include tropical (seasonal and equatorial), temperate (maritime and continental) and polar. Include the reasons for these classifications and the type of biomes found in each one.
The biome predicted by any given temperature and rainfall pattern may not develop in an area because of secondary influences or human interventions.
Consider the local biome that would develop without interference from urban or agricultural development.
The El Niño Southern Oscillation (ENSO) cycle is the fluctuation in wind and sea surface temperatures that characterizes conditions in the tropical Pacific Ocean. The two opposite and extreme states are El Niño and La Niña, with transitional and neutral states between the extremes.
Appreciate that the frequency and intensity of both El Niño and La Niña events are irregular and hard to predict.
El Niño is due to a weakening or reversal of the normal east–west (Walker) circulation, which increases surface stratification and decreases upwelling of cold, nutrient-rich water near the coast of north-western South America. La Niña is due to a strengthening of the Walker circulation and reversal of other effects of El Niño.
Consider how El Niño and La Niña events develop and also consider that the ENSO cycle affects conditions directly in the tropical Pacific Ocean and affects the climate of other regions in the tropics and subtropics indirectly. Use examples of resulting weather patterns in specific locations and the resulting changes to productivity of marine ecosystems.
Tropical cyclones are rapidly circulating storm systems with a low-pressure centre that originate in the tropics and are characterized by strong winds.
Tropical cyclones are classified as hurricanes or typhoons (the name depends on where the storm originates in the world) once sustained wind speeds exceed 119 km/hr.
Rises in ocean temperatures resulting from global warming are increasing the intensity and frequency of hurricanes and typhoons because warmer water and air have more energy.
Include evidence for increases in hurricanes and typhoons.
Zonation refers to changes in community along an environmental gradient.
Zonation occurs due to a range of factors, such as changes in elevation, latitude, tidal level, soil horizons or distance from a water source.
Transects can be used to measure biotic and abiotic factors along an environmental gradient in order to determine the variables that affect the distribution of species.
Consider data in tables or figures related to zonation, including kite graphs.
Application of skills: Investigate zonation along an environmental gradient using a transect sampling technique and a range of relevant abiotic measurements.
Create kite diagrams to show distribution.
Succession is the replacement of one community by another in an area over time due to changes in biotic and abiotic variables.
Changes occur as one community changes the environmental conditions so another community can colonize the area and replace the first through competition. This process may continue for hundreds of years; pollen records in peat provide evidence of such changes.
Zonation is a spatial phenomenon; succession is a temporal phenomenon.
Application of skills: Use secondary data and a mapping database to recreate or map the changes through succession in a given area.
Each seral community (sere) in a succession causes changes in environmental conditions that allow the next community to replace it through competition until a stable climax community is reached.
For example, mosses start soil formation on bare rock, allowing larger plants to colonize.
Primary successions happen on newly formed substratum where there is no soil or pre-existing community, such as rock newly formed by volcanism, moraines revealed by retreating glaciers, wind-blown sand or waterborne silt.
Consider an example of primary succession, which could be a well-documented example, such as Surtsey, or a local example. Use the following terms: seral communities or stages; pioneer and climax communities.
Secondary successions happen on bare soil where there has been a pre-existing community, such as a field where agriculture has ceased or a forest after an intense firestorm.
Consider an example of secondary succession, which could be a well-documented example, such as the Broadbalk Wilderness at Rothamsted, or a local example.
Energy flow, productivity, species diversity, soil depth and nutrient cycling change over time during succession.
Consider data in tables or figures related to succession and the reasons for changes in these factors.
An ecosystem's capacity to tolerate disturbances and maintain equilibrium depends on its diversity and resilience.
Consider the links between ecosystem resilience, stability, succession, diversity and human activity. For example, succession increases diversity which adds to resilience and stability, though human interference can cause a reduction in these qualities.
The type of community that develops in a succession is influenced by climatic factors, the properties of the local bedrock and soil, geomorphology, together with fire and weather-related events that can occur. There can also be top-down influences from primary consumers or higher trophic levels.
Include factors such as steep slopes restricting soil development, lack of drainage causing waterlogging, or underlying/parent rock causing ultra-basic or other extreme soil types to develop. Living organisms, such as wolves in Yellowstone Park or elephants in savannahs, influence the final community.
Patterns of net productivity (NP) and gross productivity (GP) change over time in a community undergoing succession.
In early stages of succession, GP is low due to the unfavourable initial conditions and low density of producers. The proportion of energy lost through community cell respiration or cellular respiration is relatively low too, so NP is high—that is, the system is growing and biomass is accumulating.
In later stages of succession, with an increased consumer community, GP may be high in a climax community. However, this is balanced by cell respiration or cellular respiration, so NP approaches zero.
r- and K-strategist species have reproductive strategies that are better adapted to pioneer and climax communities, respectively.
r-strategist species are those that produce large numbers of offspring so they can colonize new habitats quickly and make use of short-lived resources; K-strategist species tend to produce a small number of offspring, which increases their survival rate and enables them to survive in long-term climax communities.
The concept of a climax community has been challenged, and there is uncertainty over what ecosystems would develop naturally were there no human influences.
Consider the debate over the Vera wood-pasture hypothesis regarding the effects of primary consumers on the plant communities, or a local example. Include the concept of alternative stable states that occur due to random events.
Human activity can divert and change the progression of succession leading to a plagioclimax.
Use local examples, such as the complete removal of top carnivores and grazing by domesticated livestock.
28 subtopics
Biodiversity is the total diversity of living systems and it exists at several levels.
The biodiversity levels are habitat diversity, species diversity and genetic diversity.
The components of diversity contribute to the resilience of ecological systems.
Each component of biodiversity contributes to the resilience of living systems.
Biodiversity arises from evolutionary processes.
Evolution is cumulative change in the heritable characteristics of a population or species.
Natural selection is the mechanism driving evolutionary change.
Natural selection operates continuously and can take place over billions of years, resulting in the biodiversity of life on Earth.
Evolution by natural selection involves variation, overproduction, competition for limited resources, and differences in adaptation that affect rates of survival and reproduction.
Natural selection occurs because genetic diversity gives rise to variation within a population. Individuals with variations that provide an advantage in a given environment are more likely to survive and reproduce than others. Variation is heritable; therefore, individuals with advantageous genes can pass them on to their offspring. As a result, the frequency of advantageous genes will increase over many generations.
Speciation is the generation of new species through evolution.
Speciation takes place when a population of a species becomes isolated and adapts in different ways to their environment. Over time, they become unable to interbreed with other populations of the original species, and thus they evolve into a new species.
Species diversity in communities is a product of richness and evenness.
Richness is the number of species in a community; evenness is how similar the population sizes of each species are. Consider the significance of these two variables for biodiversity.
Simpson's reciprocal index is used to provide a quantitative measure of species diversity, allowing different ecosystems to be compared and for change in a specific ecosystem over time to be monitored.
Consider appropriate sampling procedures for comparing diversity in areas containing the same type of organism in the same ecosystem.
Calculate diversity (D) if provided with data and the formula in which N is the total number of individuals in the population and n is the number of individuals of a single species.
The value of D will be higher where there is greater richness (number of species) and evenness (similar abundance), with 1 being the lowest possible value.
Knowledge of global and regional biodiversity is needed for the development of effective management strategies to conserve biodiversity.
Include how knowledge of biodiversity is gathered in the local region. This is likely to involve citizen science and the work of voluntary and government-funded agencies. The training of indigenous people and others, such as parabiologists, is also used to gather information for use in conservation management.
Mutation and sexual reproduction increase genetic diversity.
Mutation generates new variants of genes; sexual reproduction generates new combinations of genes.
Reproductive isolation can be achieved by geographical separation or, for populations living in the same area, by ecological or behavioural differences.
Include two contemporary examples of speciation and their causes. (Examples such as giraffes are unsuitable as they illustrate evolutionary change rather than speciation.) Separation of bonobos and common chimpanzees is an example of speciation by geographical separation, and the apple maggot (Rhagoletis pomonella) is an example of behavioural separation. Consider reasons for high rates of endemism on isolated islands.
Biodiversity is spread unevenly across the planet, and certain areas contain a particularly large proportion of species, especially species that are rare and endangered.
Many biodiversity hotspots are in tropical biomes.
Human activities have impacted the selective forces acting on species within ecosystems, resulting in evolutionary change in these species.
Consider human activities that have affected natural selection, for example, climate change due to burning fossil fuels, hunting/poaching/harvesting, or creation of new habitats. Include the example of the tuskless elephants in Gorongosa, Mozambique or a local example.
Artificial selection reduces genetic diversity and, consequently, species resilience.
Include the distinction between natural selection, which is not deliberate, and artificial selection, which is the deliberate act of choosing individual plants or animals for breeding. The vulnerability of artificially selected species (livestock or crops) can be used to highlight the importance of genetic diversity to preserve resilience within a population. Consider the value of genetic diversity from both economic and environmental perspectives.
Earth history extends over a period of 4.5 billion years. Processes that occur over an extended timescale have led to the evolution of life on Earth.
Include the role of fossils in explaining the evolution of life over the geological timescale.
Earth history is divided up into geological epochs according to the fossil record.
The geological timescale is divided into eons, which are further classified into eras, periods and epochs. Changes in these time frames are marked by major geological and biological events. The division between one epoch and the next is marked by significant changes in fossils, indicating environmental changes causing many extinctions and the subsequent evolution of new species.
Mass extinctions are followed by rapid rates of speciation due to increased niche availability.
The five mass extinctions in the past have been caused by various factors, such as tectonic plate movements, super-volcanic eruption, climatic changes, sea-level changes and meteorite impact; this is in contrast with the current anthropogenic sixth mass extinction.
The Anthropocene is a proposed geological epoch characterized by rapid environmental change and species extinction due to human activity.
There is debate about the existence and beginning of the Anthropocene epoch. Various start dates have been proposed for the epoch. Suitable "golden spikes" in the geological strata marking the proposed beginning include the 1610 dip in carbon dioxide caused by the arrival of Europeans in the Americas, 1950 spherical fly ash particles and the 1964 Carbon-14 markers linked to nuclear tests.
Human impacts are having a planetary effect, which will be detectable in the geological record.
Changes to the geological record support the argument for the Anthropocene being denoted a separate epoch from the Holocene.
Consider at least four examples of evidence for the Anthropocene.
• Signals from chemical pollution that are currently accumulating in geological strata, with the potential to be preserved into the far future
• The mixing of native and non-native species, which will be represented in the fossil record
• Deposits from nuclear testing
• The modification of terrestrial and marine sedimentary systems
• Minerals created solely or primarily from human activity
Biological diversity is being adversely affected by both direct and indirect influences.
Direct threats include overharvesting, poaching and the illegal pet trade. Indirect threats include habitat loss, climate change, pollution and invasive alien species.
Most ecosystems are subject to multiple human impacts.
These impacts are increasing and their effects are amplified when combined. For example, when the impact of climate change has reduced resilience, other threats, such as invasive alien species, have more impact than if they were acting alone.
Invasive alien species can reduce local biodiversity by competing for limited resources, predation and introduction of diseases or parasites.
Consider how alien species can arrive in an ecosystem and the factors that can result in their exponential increase. Use a local example of an alien species that has become invasive and the management strategy that has been used to reduce its impact.
The global conservation status of species is assessed by the International Union for Conservation of Nature (IUCN) and is published as the IUCN Red List. Status is based on number of individuals, rate of increase or decrease of the population, breeding potential, geographic range and known threats.
Precise criteria and data are used to assign status to a species, and a sequence of conservation status ranks have been defined from least concern (LC) to extinct (EX).
Assigning a global conservation status publicizes the vulnerability of species and allows governments, non-governmental agencies and individual citizens to select appropriate conservation priorities and management strategies.
Include differences between the perspectives of governments, agencies and individuals in conservation.
Investigate three different named species: a species that has become extinct due to human activity; a species that is critically endangered; and a species whose conservation status has been improved by intervention.
For the three different named species, consider the factors that contributed to their decline and the impacts of their decline, disappearance or extinction on ecosystems and societies. Consider the conservation strategies that were employed, whether successful or not.
The tragedy of the commons describes possible outcomes of the shared unrestricted use of a resource, with implications for sustainability and the impacts on biodiversity.
The tragedy of the commons is a concept relating to the overexploitation of shared natural resources through human activity and the tension between individual self-interest and shared benefits of sustainable development.
Include two examples where a resource is overharvested (for example, fish stocks on the Grand Banks) or where an environment is contaminated (for example plastic pollution in ocean gyres).
Biodiversity hotspots are under threat from habitat destruction, which could lead to a significant loss of biological diversity, especially in tropical biomes.
Consider the implications of biodiversity distribution for conservation. For example, because tropical biomes are frequently located in developing countries, this can exacerbate the challenge of effective conservation.
Key areas that should be prioritized for biodiversity conservation have been identified on the basis of the international importance of their species and habitats.
Key biodiversity areas (KBAs) have been used to identify sites that contribute significantly to the global persistence of biodiversity. Consider at least two areas that have been prioritized and describe their importance for global biodiversity. The sites should hold species at risk of extinction or ecosystems at risk of collapse.
In KBAs, there is conflict between exploitation, sustainable development and conservation.
Include an example of such conflict, for example, reasons for the spread of palm oil plantations in Malaysia and Indonesia and the consequences for biodiversity.
Traditional indigenous approaches to land management can be seen as more sustainable but are facing challenges of population growth, economic development, climate change and a lack of governmental support and protection.
Threats to the notions of sustainability in traditional indigenous approaches come not only from the outside, but also from within as the society develops economically and aspires to follow the development model of the rest of the world. Consider threats to a named sustainable traditional indigenous land management practice.
Environmental justice must be considered when undertaking conservation efforts to address biodiversity loss.
The areas in the world expected to experience significant negative effects from the loss of biodiversity and ecosystem functions are those with large concentrations of indigenous people, whose communities may be of low income and without access to legal support. Consider one example of an indigenous or marginalized community that has been forcefully relocated from their homeland due to conservation efforts or protected habitats, which provided them with sustenance, for example, the Maasai in the Serengeti National Park.
The planetary boundary "loss of biosphere integrity" indicates that species extinctions have already crossed a critical threshold.
Consider the claim that species extinctions caused by human impacts could lead to a tipping point in the whole Earth system.
Arguments for species and habitat preservation can be based on aesthetic, ecological, economic, ethical and social justifications.
Economic arguments for preservation often involve valuation of ecotourism, of the genetic resource and commercial considerations of the natural capital. Ecological reasons may be related to the ecosystem services. Ethical arguments are very diverse and can include reference to the intrinsic or instrumental value of the species. Social arguments might highlight the importance of goods and services for the well-being of humans.
Species-based conservation tends to involve ex situ strategies, and habitat-based conservation tends to involve in situ strategies.
Ex situ measures include botanic gardens, zoos, the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) and seed banks; in situ measures include use of national parks, reserves and sanctuaries. Consider two examples of ex situ measure and two examples of in situ measures.
Sometimes a mixed conservation approach is adopted, where both habitat and particular species are considered.
The mixed approach usually invokes flagship and/or keystone species to justify the need to conserve intact habitats and landscapes. Consider an example of a mixed approach where the emphasis of in situ measures is on a particular species, for example, the Chengdu Research Base of Giant Panda Breeding.
The Convention on Biological Diversity (CBD) is a UN treaty addressing both species-based and habitat-based conservation.
The objective of the CBD is to develop national strategies for the conservation and sustainable use of biological diversity. It further aims to identify protected marine areas outside of national jurisdictions. It also includes the Nagoya Protocol, which promotes the fair and equitable sharing of genetic resources.
Habitat conservation strategies protect species by conservation of their natural environment. This may require protection of wild areas or active management.
Include one example of a habitat where active management has been required and one example of the establishment of an ecosanctuary using pest-exclusion fencing. Surrounding land use for the conservation area and distance from urban centres are important factors for consideration in conservation area design.
Effective conservation of biodiversity in nature reserves and national parks depends on an understanding of the biology of target species and on the effect of the size and shape of conservation areas.
Include edge effects and the importance of wildlife corridors for connectivity. Consider an example of a UNESCO biosphere reserve with high biodiversity and species of international conservation importance, including the designation of an appropriate area for conservation, potential human impacts and management strategies.
Include the concept of a pristine core, surrounded by buffer zones and outer transition zones that are sustainably managed.
Natural processes in ecosystems can be regenerated by rewilding.
Consider rewilding methods, for example, reintroduction of apex predators and other keystone species, re-establishment of connectivity of habitats over large areas, cessation of agriculture and resource harvesting, and minimization of human influences including by ecological management. Consider one example, such as Hinewai Reserve in New Zealand, any other appropriate rewilding project or a local example.
Conservation and regeneration measures can be used to reverse the decline in biodiversity to ensure a safe operating space for humanity within the biodiversity planetary boundary.
Measures can be taken to conserve and regenerate biodiversity at individual, collective, national and international levels.
Environmental perspectives and value systems can impact the choice of conservation strategies selected by a society.
The success of conservation and regeneration measures depend on incorporating a diversity of approaches, including community support, adequate funding, education and awareness, appropriate legislation, and scientific research. Consider also issues of environmental justice. More ecocentric perspectives may approach conservation for the intrinsic value of biodiversity and so focus on low-intervention in situ strategies; more anthropocentric/technocentric perspectives may be driven by the economic, societal value of biodiversity and thus embrace more scientific interventions involving zoos, gene banks and ecotourism.
Success in conserving and restoring biodiversity by international, governmental and non-governmental organizations depends on their use of media, speed of response, diplomatic constraints, financial resources and political influence.
Consider this claim with reference to named examples of the international, governmental and non-governmental organizations.
Positive feedback loops that enhance biodiversity and promote ecosystem equilibrium can be triggered by rewilding and habitat restoration efforts.
A positive feedback loop is a necessary condition for the emergence of alternative stable states at the community scale. Consider the role of enhanced growth and biomass, reproduction and survival of species on food web interactions.
Rewilding projects have both benefits and limitations.
Consider land-use issues concerning food production versus using areas for rewilding. Include the use of a rewilding project for example, Knepp Estate in England, the Affric Highlands in Scotland and the restocking of wildlife in the Gorongosa national park, Mozambique.
A suitable reference for other rewilding projects can be found through the Global Rewilding Alliance website or other sources.
The success of conservation or regeneration measures needs to be assessed.
Consider claims that conservation measures have successfully protected biodiversity, and consider the impact of the measures on local communities.
The success of the conservation strategy can be reviewed or evaluated at three levels.
Ecotourism can increase interdependence of local communities and increase biodiversity by generating income and providing funds for protecting areas, but there can also be negative societal and ecological impacts.
Consider the use of ecotourism in a named protected area.
36 subtopics
Movements of water in the hydrosphere are driven by solar radiation and gravity.
Heat is required for evaporation of water and is released when water condenses. Gravity causes water to drain through soil and in rivers to the sea.
The global hydrological cycle operates as a system with stores and flows.
In water cycle diagrams, stores should be shown as boxes and flows as arrows.
The main stores in the hydrological cycle are the oceans (96.5%), glaciers and ice caps (1.7%), groundwater (1.7%), surface freshwater (0.02%), atmosphere (0.001%), organisms (0.0001%).
Percentage values are approximate so there is no need to memorize them, but students should have some idea of the relative proportions.
Flows in the hydrological cycle include transpiration, sublimation, evaporation, condensation, advection, precipitation, melting, freezing, surface run-off, infiltration, percolation, streamflow and groundwater flow.
Sublimation is the transformation of ice directly to water vapour. Advection is the wind-blown movement of water vapour or condensed/frozen water droplets (clouds). Infiltration is water entering the soil. Percolation is water movement in the soil.
Application of skills: Create and use a systems diagram showing the transfers and transformations of the hydrological cycle.
Human activities, such as agriculture, deforestation and urbanization, can alter these flows and stores.
Change in land use, deforestation and urbanization often lead to reduced evapotranspiration and increased run-off, resulting in flash floods.
The steady state of any water body can be demonstrated through flow diagrams of inputs and outputs.
These can be used to calculate sustainable rates of harvesting from, for example, lakes and aquifers.
Water has unique physical and chemical properties that support and sustain life.
Include polarity, resulting in cohesion (attraction between water molecules due to hydrogen bonding), adhesion (attraction between water and other substances) and solvent properties. Also include transparency, high specific heat capacity, differences in density depending on temperature and differences in gas solubility (oxygen and carbon dioxide) depending on temperature and pressure.
The oceans act as a carbon sink by absorbing carbon dioxide from the atmosphere and sequestering it.
This process has moderated increases in atmospheric carbon dioxide from the burning of fossil fuels, but a saturation point may be reached.
Carbon sequestered in oceans over the short term as dissolved carbon dioxide causes ocean acidification; over the longer term, carbon is taken up into living organisms as biomass that accumulates on the seabed.
Seabed sediments contain inorganic carbonates and carbon compounds in organic matter that is not fully decomposed. Over millions of years, these sediments can become fossil fuels.
The temperature of water varies with depth, with cold water below and warmer water above. Differences in density restrict mixing between the layers, leading to persistent stratification.
The phenomenon of water being at its densest at 4°C means that colder water will float above it and a body of water freezes from the surface downwards, allowing freshwater ecosystems to survive beneath an insulating layer of ice.
Stratification occurs in deeper lakes, coastal areas, enclosed seas and open ocean, with a thermocline forming a transition layer between the warmer mixed layer at the surface and the cooler deep water below.
Warmer surface water and cold deep water also differ in the concentrations of dissolved oxygen and mineral nutrients.
Global warming and salinity changes have increased the intensity of ocean stratification.
The changes to stratification are most pronounced in the upper 200 metres of water. Temperature increases have had global effects. The melting of ice caps has reduced salinity in Antarctica.
Application of skills: Extract data from a database and analyse data on water temperatures with oxygen and salinity concentrations using an appropriate statistical test.
Upwellings in oceans and freshwater bodies can bring cold, nutrient-rich waters to the surface.
Upwelling is the mass, vertical movement of cold, nutrient-rich waters from the depths to the surface in response to displacement of wind-blown surface waters. Seasonal cycles of upwelling can occur in stratified lakes and in the upwelling associated with ENSO.
Thermohaline circulation systems are driven by differences in temperature and salinity. The resulting differences in water density drives the ocean conveyor belt, which distributes heat around the world and thus affects climate.
Rivers and melting ice caps bring low-salinity, low-density water into the North Atlantic. Wind-driven currents from the equator carry warm surface waters, such as the Gulf Stream, towards the North Atlantic that lose freshwater through evaporation and become more saline. The increased salinity and decreased temperature of these waters cause them to sink and form deep ocean currents back towards the equator, thereby creating the North Atlantic conveyor belt.
Water security is having access to sufficient amounts of safe drinking water.
Water security is a significant component of sustainable societies.
Social, cultural, economic and political factors all have an impact on the availability of, and equitable access to, the freshwater required for human well-being.
Include examples of social, cultural, economic and political factors that have impacts.
Human societies undergoing population growth or economic development must increase the supply of water or the efficiency of its utilization.
Water is used for domestic purposes, for irrigation and raising livestock in agriculture, and for industry.
Water supplies can be increased by constructing dams, reservoirs, rainwater catchment systems, desalination plants and enhancement of natural wetlands.
Desalination is removal of salt and other minerals from water in order to obtain freshwater. Reverse osmosis is a method of desalination using a semi-permeable membrane.
Water scarcity refers to the limited availability of water to human societies.
Water availability may be limited by the actual abundance of water present (physical scarcity) or by the available storage and transport systems (economic scarcity).
Water conservation techniques can be applied at a domestic level.
Include techniques such as metering, rationing, grey-water recycling, low-flush toilets, rainwater harvesting.
Water conservation strategies can be applied at an industrial level in food production systems.
Include examples, such as greenhouses that use and recycle harvested rainwater, aquaponics systems that combine production of fish and vegetables, drip irrigation systems, drought-resistant crops, switching to vegetarian food production.
Mitigation strategies exist to address water scarcity.
Consider appropriate examples of management strategies a named country employs to address water scarcity.
Freshwater use is a planetary boundary, with increasing demand for limited freshwater resources causing increased water stress and the risk of abrupt and irreversible changes to the hydrological system.
Consider how the planetary boundary can be measured and possible mitigation strategies to bring it back within the boundary.
Local and global governance is needed to maintain freshwater use at sustainable levels.
Include one example of local regulations on water use, such as banning watering of gardens in droughts. Include one example of where international agreements over water sources have become necessary.
Water footprints can serve as a measure of sustainable use by societies and can inform decision-making about water security.
A water footprint is a measure of the use of water by individual humans or nations, or the amount needed to grow crops or livestock or manufacture textiles, steel or other products.
Citizen science is playing an increasing role in monitoring and managing water resources.
Citizen science is also called community science or crowdsourced science. Common features of citizen science are that anyone can take part. All participants use the same protocol so that high-quality data can be combined and data is open access.
Consider the benefits and limitations of citizen science in ensuring sustainable water use at a local level. For example, consider whether it is possible to crowdsource accurate water-quality data.
“Water stress” like “water scarcity” is another measure of the limitation of water supply; it not only takes into account the scarcity of availability but also the water quality, environmental flows and accessibility.
A region may have an ample supply and not be suffering from water scarcity, but it may be experiencing water stress because of low water quality.
Water stress is defined as a clean, accessible water supply of less than 1,700 cubic metres per year per capita.
Consider one example of a society that falls below this level and the reasons that account for this.
The causes of increasing water stress may depend on the socio-economic context.
Include at least two different perspectives, such as the aim of increasing industrialization in an emerging economy and over-abstraction due to population pressure in a low-income country.
Water stress can arise from transboundary disputes when water sources cross regional boundaries.
Include at least one local or regional example of a transboundary dispute and references to the historical or political context for that conflict.
Water stress can be addressed at an industrial level.
Consider strategies of dams, water transfer, pipelines or tankers, estuary storage with barrages, rainmaking or cloud seeding, desalination, solar distillation, dew harvesting, water treatment plants, aquifer storage and recovery (ASR) and artificial recharge of aquifers (AR).
Application of skills: Use secondary data sources to investigate the causes of water stress within a given society.
Industrial freshwater production has negative environmental impacts that can be minimized but not usually eliminated.
Include the potential impacts of: concentrated brine discharges from desalination plants; noise; air pollution; impacts on aquifers (for example, saline intrusion); and combustion of fossil fuels to provide energy (for example, desalination in the United Arab Emirates (UAE)).
Inequitable access to drinkable water and sanitation negatively impacts human health and sustainable development.
Include an example of an equity issue relating to water and sanitation for a named marginalized group within society. Marginalized groups could include indigenous people or low-income groups. Include statistics providing evidence of inequity.
Phytoplankton and macrophytes provide energy for freshwater and marine food webs.
Phytoplankton are a type of microscopic plankton capable of photosynthesis that are found in oceans, seas and freshwater.
Macrophytes are aquatic plants that are large enough to be visible. They can be emergent from water, submerged or floating.
Humans consume organisms from freshwater and marine environments.
Include one local and one global example of aquatic flora and fauna consumed by humans.
Demand for foods from freshwater and marine environments is increasing due to the growth in human population and changes in dietary preferences.
Consider evidence for the increasing demand.
The increasing global demand for seafood has encouraged use of unsustainable harvesting practices and overexploitation.
Include bottom trawling, ghost fishing and the use of poisons and explosives as destructive methods of harvesting that are unsustainable.
Overexploitation has led to the collapse of fisheries.
Consider details of one fishery collapse (the dramatic and lasting decrease in stocks to a point where the commercial fish can no longer recover), for example, the cod fishery on the Grand Banks of Newfoundland.
The maximum sustainable yield (MSY) is the highest possible annual catch that can be sustained over time, so it should be used to set caps on fishing quotas.
Consider the yield/fishing effort graph indicating the MSY. Typically, harvesting at the MSY requires much lower fishing rates than occurs in many fisheries.
Climate change and ocean acidification are having impacts on ecosystems and may cause collapse of some populations in freshwater or marine ecosystems.
Include a local or global example of an aquatic ecosystem under stress due to climate change or ocean acidification, for example, the impact of coral bleaching events on the ecosystem of the Great Barrier Reef.
Application of skills: Plan an experiment to investigate the impact of acidification on shelled organisms.
Unsustainable exploitation of freshwater and marine ecosystems can be mitigated through policy legislation addressing the fishing industry and changes in consumer behaviour.
Include actions at international, national, local/individual level including permits, quotas, seasons, mesh size, zones, food labelling.
Marine protected areas (MPAs) can be used to support aquatic food chains and maintain sustainable yields.
Include how a protected area can benefit wider areas of sea, for example, by providing shelter or spawning grounds.
Aquaculture is the farming of aquatic organisms, including fish, molluscs, crustaceans and aquatic plants. The industry is expanding to increase food supplies and support economic development, but there are associated environmental impacts.
Consider a specific example of aquaculture including references to negative impacts, such as loss of habitat, pollution with feed, anti-fouling agents, antibiotics and other medicines used, spread of diseases, and escapees which, in some cases, are genetically modified. Include reference to at least one management technique that can reduce the effect of negative impacts.
Productivity, thermal stratification, nutrient mixing and nutrient loading are interconnected in water systems.
The highest productivity tends to occur near coastlines or in shallow seas, where upwellings and nutrient enrichment of surface waters occurs.
Accurate assessment of fish stocks and monitoring of harvest rates are required for their conservation and sustainable use.
Include at least one method of measuring a fish stock accurately and one method of monitoring harvest rates.
There are risks in harvesting fish at the maximum sustainable yield (MSY) rate and these risks need to be managed carefully.
The MSY is only an estimated value and attempting to harvest at exactly that rate will inevitably be inaccurate. Exceeding the rate may lead to reduction in reproductive potential and positive feedback, causing rapid decline in fish stocks.
Species that have been overexploited may recover with cooperation between governments, the fishing industry, consumers and other interest groups, including NGOs, wholesale fishery markets and local supermarkets.
Consider the perspective of each group of stakeholders and how differences can be resolved. Measures that help to restore stocks include temporary fishing bans, limits to fishing licences, prevention of bycatch and information to help consumers choose species that are not being harvested unsustainably.
According to the UN Convention on the Law of the Sea (UNCLOS), coastal states have an exclusive economic zone stretching 370 km out to sea, within which the state's government can regulate fishing. Almost 60% of the ocean is the high seas outside these coastal zones, with limited intergovernmental regulation.
There is an equity and justice issue when countries sell access to their fishing zones rather than managing it for local people. The UN has developed and signed an international treaty to protect the high seas.
Harvesting of seals, whales and dolphins raises ethical issues relating to the rights of animals and of indigenous groups of humans.
Consider the hunting of a particular species from at least two contrasting perspectives, for example, the Inuit killing of narwhals or the Faroe Islanders' killing of dolphins.
Water pollution has multiple sources and has major impacts on marine and freshwater systems.
Include reference to sewage, agricultural run-off, industrial effluent, urban run-off, solid waste disposal and oil spills as sources of pollution. Include a more detailed account of a specific example of water pollution, identifying the location, source of pollution, and the impacts on the environment and management strategies attempting to address it.
Plastic debris is accumulating in marine environments. Management is needed to remove plastics from the supply chain and to clear up existing pollution.
Include the harm that comes from oceanic plastic pollution; how plastics have come to aggregate into oceanic gyres; and how the associated microplastics that enter the food chain accumulate, magnify and transport surface toxins.
Water quality is the measurement of chemical, physical and biological characteristics of water. Water quality is variable and is often measured using a water quality index. Monitoring water quality can inform management strategies for reducing water pollution.
Water quality in aquatic systems is assessed by monitoring dissolved oxygen, pH, temperature, turbidity, and concentrations of nitrates, phosphates, specific metals and total suspended solids. Data can be used to inform management strategies for reducing pollution.
Application of skills: Use methods for measuring key abiotic factors in aquatic systems, for example, dissolved oxygen, pH, temperature, turbidity, and concentrations of nitrates, phosphates and total suspended solids. Possible methods may include the use of oxygen and pH probes, a thermometer, a Secchi disc, nitrate/phosphate tests.
Biochemical oxygen demand (BOD) is a measure of the amount of dissolved oxygen required by microorganisms to decompose organic material in water.
The usual measure is milligrams of oxygen consumed per litre of sample in five days at 20°C. BOD provides an indirect measure of the amount of organic matter within a sample.
Eutrophication occurs when lakes, estuaries and coastal waters receive inputs of mineral nutrients, especially nitrates and phosphates, often causing excessive growth of phytoplankton.
Algal blooms only occur if phytoplankton growth had previously been limited by lower concentrations of phosphate and/or nitrate. Humans cause eutrophication when releasing detergents, sewage or agricultural fertilizers into water bodies.
Eutrophication leads to a sequence of impacts and changes to the aquatic system.
Excessive growth of phytoplankton is typically followed by their death and, therefore, high rates of decomposition, rapid consumption of dissolved oxygen leading to hypoxia or anoxia in the water, and death of aquatic life that depends on dissolved oxygen occur.
Application of skills: Create a systems model to show the impacts and changes eutrophication produces in an aquatic system. This model should include examples of positive feedback (for example, increase in nutrients>increase in death of organisms>increase in decomposition>increase in nutrients).
Eutrophication can substantially impact ecosystem services.
Eutrophication can affect services associated with fisheries, recreation, aesthetics and health.
Eutrophication can be addressed at three different levels of management.
These three levels of management are:
• the reduction of human activities that produce pollutants—for example, alternatives to current fertilizers and detergents
• the reduction of the release of pollution into the environment—for example, treatment of wastewater to remove nitrates and phosphates
• the removal of pollutants from the environment and restoration of ecosystems—for example, removal of mud from eutrophic lakes and reintroduction of plant and fish species.
These methods can also apply to other examples of pollution.
There is a wide range of pollutants that can be found in water.
These pollutants may include organic matter (for example, sewage), dissolved substances (for example, tributyltin, an endocrine-disrupting chemical), persistent chemicals that become biomagnified (for example, PCBs), plastics and heat energy.
Algal blooms may produce toxins that threaten the health of humans and other animals.
Harmful algal blooms (HABs) contain a variety of organisms, including cyanobacteria, protists, algae and dinoflagellates. A small number of these organisms produce potentially fatal toxins. In freshwater, cyanotoxins are the most common toxins. Within the HABs that occur along coastlines, dinoflagellates produce different toxins, including a neurotoxin; these may be red in colour. Consider one example from freshwater and one from marine water.
The frequency of anoxic/hypoxic waters is likely to increase due to the combined effects of global warming, freshwater stratification, sewage disposal and eutrophication.
Hypoxic conditions can arise from a variety of causes, resulting in aquatic dead zones.
Sewage is treated to allow safe release of effluent by primary, secondary and tertiary water treatment stages.
Consider what is achieved in each of the sewage treatment stages, including both biological and chemical processes. Also consider the challenges of implementing sewage treatment equitably in all societies.
Some species are sensitive to pollutants or are adapted to polluted waters, so these can be used as indicator species.
Include at least one example of a tolerant and at least one example of an intolerant indicator species.
A biotic index can provide an indirect measure of water quality based on the tolerance to pollution, relative abundance and diversity of species in the community.
The Trent biotic index is an example of a biotic index.
Application of skills: Apply protocols for assessing biological oxygen demand and a named biotic index.
Overall water quality can be assessed by calculating a water quality index (WQI).
A WQI is a single, weighted average, consisting of the combined results of several individual water quality test parameters, representing the degree of contamination in a given water sample. Vernier's WQI is one example.
Drinking water quality guidelines have been set by the World Health Organization (WHO), and local governments can set statutory standards.
Consider the role of regulations and standards in environmental impact assessments and international business agreements, for example, when a private company builds a water bottling plant in a developing country.
Action by individuals or groups of citizens can help to reduce water pollution.
Include changes to consumption and waste disposal, peaceful citizen protest, data collection and research, formation of legal teams and lobbying of lawmakers.
21 subtopics
Soil is a dynamic system within the larger ecosystem that has its own inputs, outputs, storages and flows.
Soils are a resource for life and they vary widely.
Soil is made up of inorganic and organic components, water and air.
Soil is a complex mixture of interacting components forming its own ecosystem with distinct soil organisms. Inorganic components or mineral matter (rock fragments, sand, silt and clay) come from weathering of parental rock. Organic components include living organisms and material from the decay of organisms. There are keys published online to classify soils.
Soils develop a stable, layered structure known as a profile made up of several horizons, produced by interactions within the system over long periods of time.
Soil profiles have distinctive horizons that show a transition from more organic components in the upper surface to inorganic below.
Application of skills
• Sample two soils from the subsoil (B horizon): one from a local garden or field, and one from a natural ecosystem.
• Investigate texture, organic matter content, nitrogen, phosphorus, and potassium (NPK) concentrations, aeration, drainage and water retention.
• Determine the amount of carbon in a dry soil sample by burning off the organic matter and calculating the change in mass.
Soil system inputs include those from dead organic matter and inorganic minerals.
Dead organic matter inputs may include, but not be limited to, plant litter, dead animal biomass, manure.
Inorganic mineral inputs may include weathering, deposition or precipitation (water with dissolved minerals).
In managed soil systems, many inputs are anthropogenic: compost, fertilizer, agrochemicals, irrigation, salinization. Natural inputs may originate from within the ecosystem (weathering of underlying parental rock, litter from above-ground vegetation, decomposition) or be derived from other ecosystems (wind-blown and waterborne deposition, guano).
Soil system outputs include losses of dead organic matter due to decomposition, losses of mineral components and loss of energy due to heat loss.
Mineral component outputs include wind or water erosion, water and mineral absorption by plant roots, leaching of dissolved plant nutrients and water, diffusion of gases and evaporation of water.
These outputs can cause the loss or modification of soil components and are different from total loss of soil by erosion; however, they can also lead to degradation of productive soil.
Transfers occur across soil horizons, into and out of soils.
Include infiltration, percolation, groundwater flow, biological mixing, aeration, erosion and leaching.
Transformations within soils can change the components or the whole soil system.
Include decomposition, weathering, nutrient cycling and salinization.
Systems flow diagrams show flows into, out of and within the soil ecosystem.
Soil systems are essential for the water, carbon and nitrogen cycles.
Application of skills: Create a systems flow diagram representing the soil system.
Soils provide the foundation of terrestrial ecosystems as a medium for plant growth (a seed bank, a store of water and almost all essential plant nutrients). Carbon is an exception; it is obtained by plants from the atmosphere.
Soils store the key nutrients for plants: nitrogen, phosphorus and potassium.
Soils contribute to biodiversity by providing a habitat and a niche for many species.
Soil communities have a large biodiversity, including microorganisms, animals and fungi (of which there are still many unknown species).
Soils have an important role in the recycling of elements as a part of biogeochemical cycles.
The major input is of dead organic matter from the plants entering the soil. Leaf litter is then broken down by detritivores (for example, earthworms) into smaller fragments and decomposed by saprotrophs, such as fungi and bacteria.
Soil texture defines the physical make-up of the mineral soil. It depends on the relative proportions of sand, silt, clay and humus.
Soil texture can be determined using a key, a feel test or by mixing with water and separating the layers in the laboratory.
Soil texture affects primary productivity through the differing influences of sand, silt, clay and dead organic matter, including humus.
Humus contributes significantly to the texture of soils in which it is abundant. It is a dark brown or black substance lying beneath the leaf litter. It has a loose, crumbly texture formed by the partial decay of dead plant material. It influences mineral nutrient retention versus leaching, water retention versus drainage, and aeration versus compaction or waterlogging; these influences affect primary productivity.
Soils can act as carbon sinks, stores or sources, depending on the relative rates of input of dead organic matter and decomposition.
Consider why there is little carbon stored in tropical forest soils and relatively large amounts under tundra, wetlands and temperate grasslands.
Soils are classified and mapped by appearance of the whole soil profile.
Drawing a profile diagram is a useful descriptive technique used to explain how the transfer and transformation processes work on the soil components.
Application of skills: Use soil profile diagrams to classify examples of soils that can be linked to the biomes studied, for example, brown earths to temperate deciduous forests, or oxisols to rainforests.
Horizons are horizontal strata that are distinctive to the soil type. The key horizons are organic layer, mixed layer, mineral soil and parent rock (O, A, B and C horizons).
Natural soil systems have O, A, B and C horizons, but intensive agricultural systems have only B and C horizons remaining. Consider the impact of this either through looking at images or at actual examples.
The A horizon is the layer of soil just beneath the uppermost organic humus layer, where present. It is rich in organic matter and is also known as the mixed layer or topsoil. This is the most valuable for plant growth but, along with the O horizon, is also the most vulnerable to erosion and degradation, with implications for sustainable management of soil.
Topsoil has more oxygen, organic matter, microorganisms and nutrient recycling than lower soil horizons; therefore, it is where there is most root growth and other biological activity. Intensive farming removes this layer and requires the addition of fertilizers.
Factors that influence soil formation include climate, organisms, geomorphology (landscape), geology (parent material) and time.
Climate factors include contrast of temperatures from a range of biomes in tropical, temperate and polar regions.
Geomorphological factors include slope, aspect and drainage.
Geology and time factors include influences on weathering, erosion and deposition of materials, waterlogging and aeration.
Also include the influence of calcareous and volcanic parent rock types on soil formation.
Differences between soils rich in sand, silt or clay include particle size and chemical properties.
Sand and silt are derived from quartz and have a low cation-exchange capacity (CEC); clays are complex silicates that have a much greater CEC that increases availability of positively charged minerals, for example, calcium, magnesium and potassium.
Soil properties can be determined from analysing the sand, silt and clay percentages, percentage organic matter, percentage water, infiltration, bulk density, colour and pH.
Consider data on soils, including using the soil texture triangle.
Carbon is released from soils as methane or carbon dioxide.
Carbon may be released from soils through increased decomposition due to global warming, agricultural practices, drainage of wetlands or other human activity; it may lead to a tipping point. There is a tipping point where increasing temperatures lead to breakdown of methane clathrates in underlying geological structures.
Land is a finite resource, and the human population continues to increase and require feeding.
About 70% of ice-free land is used for agriculture and forestry. Not all soils or land are suitable for arable crops; some land is too steep, some soils are too nutrient-poor. These are often used for livestock production.
Marginalized groups are more vulnerable if their needs are not taken into account in land-use decisions.
Consider indigenous peoples and other groups that may be marginalized or have a low socio-economic status, such as members of a low caste or women farmers or people in low-income countries. Include a named example of marginalized people deprived of sufficient land rights to support their needs.
World agriculture produces enough food to feed eight billion people, but the food is not equitably distributed and much is wasted or lost in distribution.
It is estimated that at least one-third of food production is wasted (post-harvest, in storage, in distribution). Include the SDG goal that aims to halve food waste.
Agriculture systems across the world vary considerably due to the different nature of the soils and climates.
Soils in different biomes have very different potentials for crop types and productivity.
Agricultural systems are varied, with different factors influencing the farmers' choices. These differences and factors have implications for economic, social and environmental sustainability.
Agricultural systems can be classified in a number of ways.
• Outputs from the farm system—arable, pastoral/livestock, mixed, monoculture or diverse.
• Reasons for farming—commercial or subsistence, sedentary or nomadic.
• Types of inputs required for the farm system—intensive or extensive, irrigated or rain-fed, soil-based or hydroponic, organic or inorganic.
Application of skills: Make a detailed study of one example of a pair of named contrasting systems.
Nomadic pastoralism and slash-and-burn agriculture are traditional techniques that have sustained low-density populations in some regions of the world.
As indigenous cultures modernize and exist in higher population densities or in fixed locations, these practices become less sustainable.
The Green Revolution (also known as the Third Agricultural Revolution in the 1950s and 1960s) used breeding of high-yielding crop plants—combined with increased and improved irrigation systems, synthetic fertilizer and application of pesticides—to increase food security. It has been criticized for its sociocultural, economic and environmental consequences.
There are both positive and negative consequences of the Green Revolution, and it did not occur in all developing nations. Improved productivity depended on fixing nitrogen into synthetic fertilizers, which makes their production fossil-fuel dependent.
Synthetic fertilizers are needed in many intensive systems to maintain high commercial productivity at the expense of sustainability. In sustainable agriculture, there are other methods for improving soil fertility.
These techniques include restoring natural productivity by fallowing, using organic fertilizer from farm animals or humanure, herbal mixed leys, use of mycorrhizae, continuous cover forestry and agroforestry.
A variety of techniques can be used to conserve soil, with widespread environmental, economic and sociocultural benefits.
Soil conservation techniques are very varied and can be classified in a number of ways.
Humans are omnivorous, and diets include fungi, plants, meat and fish. Diets lower in trophic levels are more sustainable.
The yield of food per unit of land area is greater in quantity and lower in cost with crops rather than livestock. Consider to what extent plant-based diets could make agriculture more sustainable.
Current global strategies to achieve sustainable food supply include reducing demand and food waste, reducing greenhouse gas emissions from food production and increasing productivity without increasing the area of land used for agriculture.
Examples include plant-based meat substitutes, reducing nitrogen loss to the atmosphere, low methane rice, reducing methane release by ruminants, extended shelf life for food, genetic modification to boost yields or in-field solar powered fertilizer production process.
Food security is the physical and economic availability of food, allowing all individuals to get the balanced diet they need for an active and healthy life.
Consider the current extent of food security within differing regions of the world.
Contrasting agricultural choices will often be the result of differences in the local soils and climate.
Consider one pair of contrasting agricultural choices from one biome. Examples include: cereal and ranching in the mollisols of steppe and prairies; soya beans and cattle ranching in the oxisols of tropical forests; ranching and irrigated crops in desert aridisol farming; or mixed arable and pasture in temperate forest brown earths.
Numerous alternative farming approaches have been developed in relation to the current ecological crisis. These include approaches that promote soil regeneration, rewilding, permaculture, non-commercial cropping and zero tillage.
Alternative approaches have been developed to address a variety of issues, including food sustainability, water quality, local economic stability, as well as restoring and conserving soils.
Regenerative farming systems and permaculture use mixed farming techniques to improve and diversify productivity. Techniques include the use of animals like pigs or chickens to clear vegetation and plough the land, or mob grazing to improve soil.
Consider the advantages and disadvantages of these techniques. Consider how plant-based diets could be part of regenerative and permaculture farming systems.
Technological improvements can lead to very high levels of productivity, as seen in the modern high-tech greenhouse and vertical farming techniques that are increasingly important for supplying food to urban areas.
Improvements to agriculture in the 21st century can greatly improve productivity, but these are not always sustainable as they may be dependent on fossil fuels.
The sustainability of different diets varies. Supply chain efficiency, the distance food travels, the type of farming and farming techniques, and societal diet changes can all impact sustainability.
Consider the environmental impacts of: the length of a supply chain (social, economic and physical distance); year-round food supply and the associated food miles; the cultural shifts to eating more or less meat; and the rise in veganism. For example, the planetary health diet (PHD) developed by the Eat-Lancet Commission.
Application of skills: Create a survey to investigate food preferences and the worldviews of various groups.
Harvesting wild species from ecosystems by traditional methods may be more sustainable than land conversion and cultivation.
Consider the claim that harvesting by traditional methods may be more sustainable. A variety of secondary forest products could be harvested, for example, Brazil nuts (Bertholletia excelsa), truffles (subterranean fungi), bamboo shoots, honey and insects for food. Also include the harvesting of controversial and endangered species, such as pangolins, bears or other bushmeats.
Claims that low-productivity, indigenous, traditional or alternative food systems are sustainable should be evaluated against the need to produce enough food to feed the wider global population.
Consider the view that low-productivity subsistence systems that have little commercial value can resolve the problem of global unsustainability in food production.
Food distribution patterns and food quality variations reflect functioning of the global food supply industry and can lead to all forms of malnutrition (diseases of undernourishment and overnourishment).
Uneven distribution of food and variations in food quality cause health issues; care should be taken to avoid assuming biomass correlates with nutritive value—food can be low nutritive quality or highly processed. Famine is caused as much by distribution problems as crop failure. Examples include the Irish potato famine (1845–49) caused by potato blight, and East Africa famines caused by drought and conflict.
30 subtopics
The atmosphere forms the boundary between Earth and space. It is the outer limit of the biosphere and its composition and processes support life on Earth.
The atmosphere includes a mixture of gases; these gases are redistributed through physical processes, such as wind.
Differential heating of the atmosphere creates the tricellular model of atmospheric circulation that redistributes the heat from the equator to the poles.
This circulation disperses the heat across the planet, reducing the heat at the equator and increasing the temperature in higher latitudes.
Application of skills: Create system diagrams to represent the atmospheric system.
GHGs and aerosols in the atmosphere absorb and re-emit some of the infrared (long-wave) radiation emitted from the Earth's surface, preventing it from being radiated out into space. They include the greenhouse gases water vapour, carbon dioxide, methane and nitrous oxide (N₂O), and black carbon (aerosol).
Carbon dioxide and water vapour are the most abundant GHGs in the atmosphere, and methane also has significant warming effects. Other gases also contribute to radiative forcing. Although water vapour is a significant GHG, it is usually excluded from climate models as its abundance changes as a result of global warming; it is dynamic within the atmospheric system and is essential for life, so cannot be mitigated against.
The greenhouse effect keeps the Earth warmer than it otherwise would be due to the broad spectrum of the Sun's radiation reaching the Earth's surface and infrared radiation emitted by the warmed surface then being trapped and re-radiated by GHGs.
The greenhouse effect is a natural process that keeps the Earth warm enough for life to be possible. The temperature of the Earth depends on the concentration of GHGs in the atmosphere. The term "enhanced greenhouse effect" has been used in reference to the accumulation of GHGs by human activity leading to global warming (increasing mean global temperature). "Climate change" encompasses global warming but refers to the broader range of changes that are happening to the planet as a result.
The atmosphere is a dynamic system, and the components and layers are the result of continuous physical and chemical processes.
For physical processes, include global warming, and air movements due to temperature and pressure differences. For chemical processes, include production of ozone from oxygen.
Molecules in the atmosphere are pulled towards the Earth's surface by gravity. Because gravitational force is inversely proportional to distance, the atmosphere thins as altitude increases.
Include standard lapse rate (about one degree for every 100 m altitude). Quantifying volumes or pressures of gases at specific altitudes is not required.
Milankovitch cycles affect how much solar radiation reaches the Earth and lead to cycles in the Earth's climate over tens to hundreds of thousands of years.
There is a relationship between the three types of Milankovitch cycles (the shape of Earth's orbit; angle of tilt; and axis of rotation) and the corresponding climate changes. Through positive feedback loops, this causes either decreasing concentrations of atmospheric carbon dioxide with cooling and glaciation or increasing carbon dioxide concentrations with warming and interglacial conditions. These cycles occur over many thousands of years but do not explain current warming.
Global warming is moving the Earth away from the glacial–interglacial cycle that has characterized the Quaternary period, toward hotter climatic conditions.
The Quaternary period started 2.5 million years ago. Climate has changed over geological time without human influence, but current anthropogenic changes are unprecedentedly rapid and are part of the Anthropocene epoch.
Application of skills: Investigate the impact of albedo or different GHGs on the temperature of a closed system.
The evolution of life on Earth changed the composition of the atmosphere, which in turn influences the evolution of life on Earth.
The percentage composition of the pre-biotic Earth's atmosphere was very different to current composition. Photosynthesis has decreased the carbon dioxide concentration and increased the oxygen concentration, allowing stratospheric ozone to form and for the oxidation of metals, for example, the formation of iron ore. The chronology of oxygenation in the history of the Earth is not required.
Climate describes the typical conditions that result from physical processes in the atmosphere.
The main factors impacting climate in an area are seasonal variations in temperature and precipitation.
Anthropogenic carbon dioxide emissions have caused concentrations of atmospheric carbon dioxide to rise significantly. The global rate of emission has accelerated, particularly since 1950.
Increases can be traced back to the start of the Industrial Revolution in late 18th-century Europe, with the main acceleration through the 20th century with the spread of industrialization and human population increase.
Analysis of ice cores, tree rings and deposited sediments provide data that indicates a positive correlation between the concentration of carbon dioxide in the atmosphere and global temperatures.
Application of skills: Investigate graphs of data for the past 800,000 years and show how these variables have changed during the glacial cycles.
The greenhouse effect has been enhanced by anthropogenic emissions of GHGs. This has led to global warming and, therefore, climate change.
Human activity has caused emissions into the atmosphere of large quantities of carbon dioxide, methane and nitrous oxide, and smaller quantities of other GHGs.
Climate change impacts ecosystems at a variety of scales, from local to global and affects the resilience of ecosystems and leads to biome shifts.
Include alteration to individual ecosystems, such as coral bleaching and desertification as local impacts, and changes to ocean circulation and sea-level rise as global impacts.
Consider a range of climate change impacts on regions where natural productivity may increase, and consider the factors that have an impact on the resilience of an ecosystem, particularly biodiversity.
Use local real-world examples to emphasize the changes.
Application of skills: Investigate climate graphs for different global locations. Atmospheric and oceanic CO₂ levels in long-term graphs provide evidence for anthropogenic global warming and ocean acidification. Use databases to explore the impact of temperature change on a specific ecosystem, for example, coral reefs or forests.
Climate change has an impact on (human) societies at a variety of scales and socio-economic conditions. This impacts the resilience of societies.
Consider a range of climate change impacts on societies where changes to health, water supply, agriculture, infrastructure and the factors that have an impact on the resilience of a society may occur.
Use local real-world examples to emphasize the changes.
Systems diagrams and models can be used to represent cause and effect of climate change with feedback loops, either positive or negative, and changes in the global energy balance.
Include solar radiation variations, terrestrial albedo changes and methane gas release with their associated feedback loops.
Evidence suggests that the Earth has already passed the planetary boundary for climate change.
Consider published evidence that addresses this assertion.
Perspectives on climate change for both individuals and societies are influenced by many factors.
Consider different perspectives on a society's response to climate change. Include personal perspectives.
Data collected over time by weather stations, observatories, radar and satellites provides opportunity for the study of climate change and land-use change. Long-term data sets include the recording of temperature and greenhouse gas (GHG) concentrations. Measurements can be both indirect (proxies) and direct. Indirect measurements include isotope measurements taken from ice cores, dendrochronology and pollen taken from peat cores.
Both direct and indirect measurements have roles in creating climate models.
Global climate models manipulate inputs to climate systems to predict possible outputs or outcomes using equations to represent the processes and interactions that drive the Earth's climate. The validity of the models can be tested via a process known as hindcasting.
There is uncertainty about the inputs (for example, the use of proxy data) and, as a result, over the outputs from the system, leading to a range of possible future outcomes. Hindcasting runs the models backwards from the present time to check the validity of the model.
Climate models use different scenarios to predict possible impacts of climate change.
Consider data showing different scenarios, such as sea-level rise, local temperature and precipitation patterns.
Climate models show the Earth may approach a critical threshold with changes to a new equilibrium. Local systems also have thresholds or tipping points.
Global critical thresholds may be rapid, unanticipated and potentially catastrophic. Critical thresholds are often referred to as tipping points. Consider the impact of positive feedback loops leading to tipping points and thresholds being crossed in at least one example. Examples include the melting of the Antarctic ice sheets, the slowing of the Atlantic thermohaline circulation, and the Amazon Rainforest–Cerrado transition (CAT).
Individual tipping points of the climate system may interact to create tipping cascades.
The interactions of two or more individual tipping points make predictions of the scale and pace of climate change very uncertain.
Individual tipping points can be biotic, abiotic or a combination of biotic/abiotic factors.
Countries vary in their responsibility for climate change and also in vulnerability, with the least responsible often being the most vulnerable. There are political and economic implications and issues of equity.
Consider both current emission rates and cumulative totals since the start of the Industrial Revolution. Also consider emissions per person and per country. Include which countries are most vulnerable to negative impacts of climate change and the associated environmental changes, and the implications of this on climate justice.
To avoid the risk of catastrophic climate change, global action is required, rather than measures adopted only by certain states.
Consider the concept of state sovereignty and the subsequent need for international cooperation through negotiation, protocols, conventions and treaties. Include an awareness of the various UN treaties and protocols addressing climate change. Include the possibility of sanctions such as cross-border carbon taxes.
Decarbonization of the economy means reducing or ending the use of energy sources that result in CO₂ emissions and their replacement with renewable energy sources.
Include the concept of carbon neutrality and the varied dates that states have set for achieving this.
A variety of mitigation strategies aim to address climate change.
There are three main categories of mitigation strategies.
• Reducing the process of global warming—for example, making household changes, large scale geoengineering interventions.
• Reducing production of GHGs—for example, energy-efficiency measures, renewable energy, food choice changes, agriculture changes, carbon tax.
• Removing CO₂ from the atmosphere—for example, through carbon sinks, rewilding, afforestation, carbon capture and storage.
Consider at least two examples from each category.
Adaptation strategies aim to reduce adverse effects of climate change and maximize any positive consequences.
There are two main categories of adaptation strategies.
Individuals and societies on a range of scales are developing adaptation plans, such as National Adaptation Programmes of Action (NAPAs), and resilience and adaptation plans.
The UN Development Programme provides a process whereby developing countries can obtain assistance to develop local priority activities to address the imminent consequences of climate change.
Responses to climate change may be led by governments or a range of non-governmental stakeholders. Responses may include economic measures, legislation, goal setting commitments and personal life changes.
Economic measures include putting a price on carbon, emissions trading and the use of subsidies and tariffs. Legislation includes country-specific legislation to reduce carbon emissions. Goal setting includes mechanisms such as B Corp branding and company goals to reduce carbon emissions and change to renewable energy sources. Personal life changes may include reducing waste production, meat consumption and energy consumption
Consider one example for each of these categories: economic, legislative, industry. Consider their impact.
Application of skills: Investigate mitigation and adaptation policies of the regional or national government.
The UN has played a key role in formulating global strategies to address climate change.
These have largely been led by the United Nations Framework Convention on Climate Change (UNFCCC) through the Intergovernmental Panel on Climate Change (IPCC) and subsequent Conference of the Parties (COP) summits. The role of the UNFCCC is to stabilize greenhouse gas concentrations at a level that prevents interference with the climate system. Consider the outcomes of the most recent COP summit. The Kigali Amendment was used to control hydrofluorocarbons (HFCs) allowed by the Montreal Protocol, but which subsequently proved to be GHG emissions.
The IPCC has proposed a range of emissions scenarios with targets to reduce the risk of catastrophic climate change.
The IPCC has five scenarios for future GHG emissions. There is uncertainty about how emissions by countries may change, leading to the five scenarios in the IPCC model.
Application of skills: Investigate graphs of the IPCC scenarios and their implications.
Technology is being developed and implemented to aid in the mitigation of climate change.
Socially embedded technologies include those used in smart cities, such as mobile apps or sensors that allow citizens to choose the nearest charging station or recycling centres. Industries supported by research and development centres in universities are developing new technology that is more efficient at reducing or removing carbon emissions. Consider the implementation of one technology to mitigate climate change in a named society.
There are challenges to overcome in implementing climate management and intervention strategies.
Include the following challenges and barriers.
• Lack of belief that climate change is a serious problem
• Lack of financial resources or planning strategies from national governments
• Lack of leadership from a range of stakeholders—for example, individuals, NGOs, political leaders, transnational companies
• International inequalities—for example, economies that profit from fossil fuels and those that do not, societies in low-income and high-income countries
• Differences in perspective between younger and older, coastal/low-lying and inland/upland communities
Geoengineering is a mitigation strategy for climate change, treating the symptom not the cause.
Geoengineering is a deliberate and large-scale intervention in the Earth's climate system, including but not limited to measures such as space mirrors, ocean fertilization, stratospheric aerosols, cloud seeding, burning biomass with carbon capture and storage. However, it has disadvantages, such as potential high costs, uncertainty of impacts, political hesitancy, lack of convincing trials and the potential for geopolitical conflict. Consider arguments for and against the potential of geoengineering.
A range of stakeholders play an important role in changing perspectives on climate change.
Consider how a range of stakeholders can influence an individual's perspectives on climate change. For example, stakeholders can include a charismatic individual, a local community group, NGOs, media and educational institutions.
Perspectives on the necessity, practicality and urgency of action on climate change will vary between individuals and between societies.
Consider differences in perspective between age groups, developed and developing societies, coastal and inland communities, and economies that profit from fossil fuels and those that do not.
The concept of the tragedy of the commons suggests that catastrophic climate change is likely unless there is international cooperation on an unprecedented scale.
The atmosphere is common to all, but when one nation benefits from an action that harms the atmosphere (for example, burning of fossil fuels), the costs are shared by all nations and their ecosystems. The reverse scenario is also true: the costs of restoring the atmosphere (for example, by carbon capture and storage) might be borne by a single nation, but the benefits are gained by all nations.
The Sun emits electromagnetic radiation in a range of wavelengths, from low frequency radio waves to high frequency gamma radiation.
Consider infrared/visible light/ultraviolet (UV) and the role they have in the biosphere.
Shorter wavelengths of radiation (namely, UV radiation) have higher frequencies and, therefore, more energy, so pose an increased danger to life.
UVA, UVB and UVC radiation damages organisms. Stratospheric ozone protects Earth by absorbing all incident UVC (which has the shortest wavelength) and most UVB rays.
Stratospheric ozone absorbs UV radiation from the Sun, reducing the amount that reaches the Earth's surface and, therefore, protecting living organisms from its harmful effects.
UV is damaging because it is high-energy radiation, especially the shortest wavelengths.
UV radiation reduces photosynthesis in phytoplankton and damages DNA by causing mutations and cancer. In humans, it causes sunburn, premature ageing of the skin and cataracts.
Consider data related to impacts of UV radiation.
The relative concentration of ozone molecules has stayed constant over long periods of time due to a steady state of equilibrium between the concurrent processes of ozone formation and destruction.
The use of chemical symbols, formulae or equations for the equilibrium of ozone is not required.
Ozone-depleting substances (ODSs) destroy ozone molecules, augmenting the natural ozone breakdown process.
When rates of ozone formation and depletion are unequal, the equilibrium will tip to increase in formation or destruction. Ozone depletion is not a cause of global warming.
HL only: Chemical equations relating to the formation and destruction of ozone are required.
Ozone depletion allows increasing amounts of UVB radiation to reach the Earth's surface, which impacts ecosystems and human health.
Ozone depletion has affected the stratosphere over the whole Earth. At the poles, ozone "holes" with greater depletion appear every spring due to the effects of ODSs and seasonal atmospheric weather patterns.
The Montreal Protocol is an international treaty that regulates the production, trade and use of chlorofluorocarbons (CFCs) and other ODSs. It is regarded as the most successful example yet of international cooperation in management and intervention to resolve a significant environmental issue.
Consider why the Montreal Protocol has been a success in reversing stratospheric ozone depletion and possible applications to other areas where international cooperation is necessary.
Actions taken in response to the Montreal Protocol have prevented the planetary boundary for stratospheric ozone depletion being crossed.
Consider data relating to the ozone hole over time as evidence for this conclusion.
ODSs release halogens, such as chlorine and fluorine, into the stratosphere, which break down ozone.
CFCs and other ODSs have been produced and released into the atmosphere, particularly carbon compounds that break down to release highly reactive fluorine and chlorine.
Polar stratospheric ozone depletion occurs in the spring due to the unique chemical and atmospheric conditions in the polar stratosphere.
Contributing chemical and atmospheric conditions include volcanic aerosols and polar stratospheric clouds, as well as the presence of "active surfaces" in the polar stratosphere upon which ozone destruction reactions can be enhanced.
Hydrofluorocarbons (HFCs) were developed to replace CFCs as they can be used in similar ways and cause much less ozone depletion, but they are potent GHGs. They have since been controlled by the Kigali Amendment to the Montreal Protocol.
CFCs and HFCs have been used in aerosols and as coolants in refrigerators and air conditioning systems. Unless carefully collected from redundant appliances, they leak into the atmosphere.
Air conditioning units are energy-intensive, contribute to GHG emissions and traditionally have contained ODSs.
Include the development of substitute refrigerants and alternatives, such as improved building design, greening and rewilding of cities.
Application of skills: Review the alternatives to air conditioning units. Use databases to collect data on the use of air conditioning units in different societies and present this data graphically, considering the reasons for the differences per capita.
19 subtopics
Natural resources are the raw materials and sources of energy used and consumed by society.
These include sunlight, air, water, land, rocks, ecosystems and living things.
Natural capital is the stock of natural resources available on Earth.
Consider local examples of three types of natural capital.
Natural capital provides natural income in terms of goods and services.
Examples of natural income goods include fish or timber. Example of natural income services include climate regulation and flood prevention.
The terms “natural capital” and “natural income” imply a particular perspective on nature.
Consider the implications of regarding nature as being made up of natural capital, services and resources. This perception in itself might be associated with the contentious philosophical perspective that nature is there for human exploitation (more extreme anthropocentrism). However, it serves very effectively as a model for sustainable use of resources.
Natural capital has aesthetic, cultural, economic, environmental, health, intrinsic, social, spiritual and technological value. The value of natural capital is influenced by these factors.
Consider the distinction between each of these types of value and give an example.
Application of skills: Create a survey to investigate the value that members of the school community place on different ecosystem services.
The value of natural capital is dynamic in that it can change over time.
Include a variety of reasons for both increases and decreases in value, along with two named examples of change over time. Consider, for example, coal, lithium, cobalt, whale oil, cork.
Ecosystems provide life-supporting ecosystem services.
Include water replenishment, flood and erosion protection, pollution mitigation (for example, reed bed buffer zones to remove inorganic nutrients) and carbon sequestration. These ecosystem services support all living things, including humans.
All resources are finite. Resources can be classified as either renewable or non-renewable.
Renewable resources can be regenerated and/or replaced as fast as they are being used, either through natural growth or reproduction (for example, food, crops or timber) or through other recurring processes (for example, freshwater or ozone). If renewable resources are used beyond their regeneration rate, their use becomes unsustainable and they become a non-renewable resource.
The use of natural capital needs to be managed in order to ensure sustainability.
The long-term well-being of ecosystems and humans depends on resources not being used more rapidly than they can be regenerated, and on waste products not being released more rapidly than they can be transformed. Include examples to illustrate how ecosystems and societies could be harmed by excessive harvesting of resources and by the release of polluting waste products.
Resource security depends on the ability of societies to ensure the long-term availability of sufficient natural resources to meet demand.
Consider the extent to which resource security in two contrasting named societies has been achieved for food or water.
The choices a society makes in using given natural resources are affected by many factors and reflect diverse perspectives.
Factors affecting such choices may include economic, sociocultural, political, environmental, geographical, technological and historical factors. International agreements cutting GHG emissions with the aim of achieving net zero emissions changes the priority of these choices. Consider factors affecting the local choice of a named natural resource.
A range of different management and intervention strategies can be used to directly influence society's use of natural capital.
Government management could include national action plans for SDGs.
Government intervention could include strategies to reduce or stop the use of certain natural capital goods and services such as taxes, fines and legislation. For example, increasing the price of fossil fuels and carbon emission restrictions.
Government intervention could encourage the use of certain natural capital goods and services with subsidies, legislation, publicity campaigns, research and education.
For example, manufacturing concrete that stores carbon dioxide, recyclable wind turbines, biological production of ammonia replacing the Haber process.
NGOs, local communities and social movements can influence society through campaigns, social media or actions, such as recycling.
The SDGs provide a framework for action by all countries in global partnership for natural resources use and management.
Consider two relevant examples pertaining to sustainable resource management. Detailed knowledge of each goal is not required.
Sustainable resource management in development projects is addressed in an environmental impact assessment (EIA).
An EIA assesses the environmental, social and economic impacts and sustainability of a development project through independent, detailed surveys, followed by audits and continued monitoring after project completion.
Countries and regions have different guidance on the use of EIAs.
Baseline studies are generally used to predict and evaluate possible impacts of a project and suggest mitigation strategies to alleviate or avoid environmental harm. Consider a range of appropriate parameters that might be addressed by an EIA for a given project. Exploring a given EIA in depth is not required.
Making EIAs public allows local citizens to have a role as stakeholders in decision-making.
Consider the relative merits of engaging all stakeholders in decision-making for development projects.
While a given resource may be renewable, the associated means of extracting, harvesting, transporting and processing it may be unsustainable.
Consider one example of unsustainable extraction, harvesting, transporting and processing, for example, timber, fishing, hydropower.
Economic interests often favour short-term responses in production and consumption which undermine long-term sustainability.
Consider one example of resources that have been depleted by excessive consumption, such as whales, fish stocks, forests.
Natural resource insecurity hinders socio-economic development and can lead to environmental degradation and geopolitical tensions and conflicts.
Geopolitical power dynamics change if resource use changes. Oil production is centred on member countries of the Organization of the Petroleum Exporting Countries (OPEC). Most mining for minerals, such as lithium, cobalt and rare earth elements (for use in, for example, batteries and mobile phones), is in Australia, China, Chile and the Democratic Republic of the Congo (DRC). Nearly all processing of these minerals is in China. Consider one example where resource insecurity may have led to hindered development, environmental harm, geopolitical problems or conflict.
Resource security can be brought about by reductions in demand, increases in supply or changing technologies.
Demand can be reduced through increased efficiency of use or conservation measures. Reliance on imported resources can be reduced by technological shifts. Consider one example of increasing resource security in each of food, water and energy.
Economic globalization can increase supply, making countries increasingly interdependent, but it may reduce national resource security.
Provide examples in different contexts, including food, water and energy.
Application of skills: Use secondary data sources, such as Gapminder, Our World in Data and World Bank to investigate the use of a named resource (for example, steel, concrete or inorganic fertilizer) by two different societies. Use graphs and statistical tests to show results.
Energy sources are both renewable and non-renewable.
Renewable energy sources include wind, solar, tidal, wood, geothermal, hydropower. Non-renewable sources include nuclear and fossil fuels. Most of the energy released from these sources is converted to electricity.
Global energy consumption is rising with increasing population and with per capita demand.
Globally, most energy is supplied by fossil fuels, although energy supplied from renewables is increasing. The role of fossil fuels in supporting the steel, concrete and synthetic fertilizer industries suggests dependence on them is likely to continue for some time in the future. How energy supply can meet ever-growing demand is a challenge that has to be addressed by changing energy production resources and reducing consumption. Consider the changes globally and locally, and the reasons for these changes.
The sustainability of energy sources varies significantly.
Consider the relative sustainability of fossil fuels, rare earth elements, nuclear, solar and one other renewable source.
The use of both non-renewable and renewable energy sources have an environmental cost that includes environmental restoration.
Non-renewable examples include extraction of fossil fuels, refining of crude oil, liquefaction of natural gas, mining of uranium.
Examples of devices for using renewable energy sources include wind turbines; solar panels; tidal barrages and their related difficulties of construction, transportation, and recycling of these products in end-of-life management.
A variety of factors will affect the energy choices that a country makes.
Consider the advantages and disadvantages of the energy sources that may influence the energy choices of two contrasting named countries. Include sustainability, economic cost, pollution, energy efficiency, availability and energy security issues.
Intermittent energy production from some renewable sources creates the need for energy storage systems.
For example, wind power requires the wind to blow, and this is intermittent. Solutions to “peak-shaving” (levelling out peaks in demand) to ensure supply meets demand include batteries, pumped hydroelectricity storage (PHS), fuel cells, thermal storage. Consider one example of storage solutions.
Energy conservation and energy efficiency may allow a country to be less dependent on importing a resource.
Energy conservation is changing our behaviours to reduce consumption of energy. Examples include turning off lights, reducing use of heating or air conditioning, and travelling less by fuel-driven vehicles. It is also about increased energy-efficient technologies, such as designing housing to conserve or remove heat, low energy intelligent lighting, designing shipping with sails, or designing goods to be easily recycled (circular economy). Consider the effectiveness of two examples of energy conservation or energy efficiency.
Energy security for a country means access to affordable and reliable sources of energy.
Through energy-efficiency measures, decreasing reliance on imported energy supplies and diversification, a country can improve its energy security.
Application of skills: Investigate graphical representations of how use of energy sources changes over time, both globally and by country. Compare these changes and their impacts.
Investigate secondary data sources, such as Gapminder, Our World in Data and World Bank, to compare the types and amount of energy used by different societies.
Use graphs and statistical tests to show results.
The global economy mostly depends on finite reserves of fossil fuels as energy sources; these include coal, oil and natural gas.
Consider the factors influencing timelines for final depletion of these fuels, for example, the rate of consumption, discovery of new deposits, developments in technology for extraction, increased use of renewables or nuclear power.
Nuclear power is a non-renewable, low-carbon means of electricity production.
Most nuclear power stations obtain energy by fission reactions of uranium or plutonium. Although construction costs are high, once constructed, nuclear power stations produce low-cost, constant, low-carbon energy. Disadvantages are that mining for uranium has negative effects, thermal pollution from power stations changes water chemistry, there is a risk of nuclear accidents and radioactive waste is produced. This waste is stored indefinitely in containers that shield the environment from radiation.
Battery storage is required on a large scale to meet global requirements for reduction of carbon emissions, but it requires mining, transporting, processing and construction, all of which produce emissions and pollution, and cause sociopolitical tensions.
The main elements and oxides required to produce effective batteries are lithium, cobalt and rare earth elements. Their mining and processing create toxins and pollution, both on land and in the oceans, and mine tailings dam failures have occurred. Distribution of these elements is concentrated in certain countries, but demand is global, which causes unintended consequences, such as geopolitical conflicts. Consider the use of one of these elements in batteries.
Use of natural resources generates waste that can be classified by source or type.
Include domestic, industrial and agricultural as sources of waste, and e-waste, food and biohazardous materials as types of waste.
Solid domestic waste (SDW) typically has diverse content.
Include paper, cardboard, glass, metal, plastics, organic (kitchen or garden), packaging, construction debris and clothing.
The volume and composition of waste varies over time and between societies due to socio-economic, political, environmental and technological factors.
Include examples of socio-economic, political, environmental and technological factors affecting the volume and composition of waste.
The production, treatment and management of waste has environmental and social impacts, which may be experienced in a different location from where the waste was generated.
Some waste is transported long distances, usually from high-income to low-income countries, and involves potential environmental injustice.
Ecosystems can absorb some waste, but pollution occurs when harmful substances are added to an environment at a rate faster than they can be degraded or transformed into harmless substances.
The ability of ecosystems to process waste depends on factors such as the biodegradability of substances (how quickly they are broken down by biological processes) and their half-lives (the time it takes for half of a substance to decay or lose its activity). Persistent pollutants with long half-lives or low biodegradability accumulate and can cause long-term environmental harm.
Preventative strategies for waste management are more sustainable than restorative strategies.
Preventative strategies include altering human behaviour (for example, reduced consumption) or controlling the release of pollutants (for example, waste disposal).
Restorative strategies include the clean-up and restoration of damaged systems (for example, attempts to restore oceanic garbage patches).
Reduction in the consumption of goods and, therefore, production of waste is the most sustainable option.
Different waste disposal options have different advantages and disadvantages in terms of their impact on societies and ecosystems.
Consider the relative merits and demerits of landfill, incineration, waste to energy, exporting waste, recycling and composting.
Sustainable options for management of SDW can be promoted in societies.
Strategies for promoting more sustainable management include taxes, incentives, social policies, legislation, education, campaigns and improved access to disposal facilities.
The principles of a circular economy provide a holistic perspective on sustainable waste management.
Include an example (including the path of a resource) from manufacture through to appropriate product recovery strategies.
20 subtopics
Births and immigration are inputs to a human population.
Crude birth rate (number of live births per 1,000 people in a population per year) and immigration rate (number of immigrants per 1,000 population per year) are the quantitative measures of population input. The rates can be used at a variety of scales—from small urban areas, like a town, to a country to a region or to the global population.
Deaths and emigration are outputs from a human population.
Crude death rate (number of deaths per 1,000 people in a population per year) and emigration rate (number of emigrants per 1,000 population per year) are the quantitative measures of population output. The rates can be used at a variety of scales—from small urban areas, like a town, to a country to a region or to the global population.
Population dynamics can be quantified and analysed by calculating total fertility rate, life expectancy, doubling time and natural increase.
Total fertility rate is the average number of births per woman of childbearing age.
Life expectancy is the average number of years that a person can be expected to live, usually from birth, if demographic factors remain unchanged.
Doubling time is the number of years it would take a population to double its size at its current growth rate; it can be calculated by using the rule of 70. To do this, divide 70 by the growth rate (as a percentage).
Natural increase is birth rate minus death rate, expressed as a number per 1,000 or as a percentage (the birth rate minus the death rate is divided by 10).
Application of skills: Work out natural increase rates and doubling times from given data.
The global human population has followed a rapid growth curve. Models are used to predict the growth of the future global human population.
UN projection models indicate three scenarios linked to future fertility rates. There is uncertainty about how future human fertility rates may change, leading to the three scenarios in the models.
Population and migration policies can be employed to directly manage growth rates of human populations.
These may be anti-natalist or pro-natalist, thereby directly addressing birth rates, or they may address immigration and emigration. These policies may use a variety of cultural, religious, economic, social and political factors to achieve their aims. Include named examples.
Human population growth can also be managed indirectly through economic, social, health, development and other policies that have an impact on births, deaths or migration.
Many development policies addressing areas such as, but not limited to, gender equality, education, improvements in public health and welfare will indirectly affect births, deaths and migration. Include two named examples.
The composition of human populations can be modelled and compared using age–sex pyramids.
The pyramid is measured in absolute numbers or as a percentage of the total population. It shows the proportion of the population of either gender in each age group.
The demographic transition model (DTM) describes the changing levels of births and deaths in a human population through different stages of development over time.
There are five stages of the DTM, including death and then birth rates declining to produce an exponential increase, stabilization and possible decline in population. Consider the relationship of specific age–sex pyramids to appropriate stages.
Rapid human population growth has increased stress on the Earth's systems.
Include current projections for the total human population over the next 50 and 100 years, and the factors that can change these projections. The increased stress on Earth's systems is related to biocapacity disparity and to the crossing of social foundation and planetary boundaries as illustrated in the doughnut economics model.
Age–sex pyramids can be used to determine the dependency ratio and population momentum.
The dependency ratio depends on the number of people in the ages defined as dependent (under 15 years and over 64 years) and economically productive (15–64 years) in a population. The dependency ratio tends to be high in populations with a very high or a very low fertility rate.
Population momentum is why a population will continue to grow even if the fertility rate declines. Population momentum occurs because it is not only the number of children per woman that determines population growth, but also the number of women of reproductive age.
The reasons for patterns and trends in population structure and growth can be understood using examples of two countries in different stages of the DTM.
Consider the patterns and trends from the past (at least 30 years or more ago), the present and into the future (at least 30 years). Consider reasons—historical, cultural, religious, economic, social and political factors—for the countries selected.
Environmental issues such as climate change, drought and land degradation are causing environmental migration.
Migration as a result of climate change may be due to sudden onset events, such as flooding, droughts, forest fires and intensified storms, but it is increasingly resulting from slow onset events, such as desertification, sea-level rise and saltwater inundation.
Include one example of an area where migration occurs/occurred due to an environmental issue, for example, increased migration from Tuvalu to New Zealand due to impacts of climate change on islands; repeated cyclones that have caused local devastation and emigration from Mozambique.
Application of skills: Use secondary data from sources such as Gapminder, World Bank and Our World in Data to test a hypothesis about the relationship between a socio-economic indicator and a demographic factor using a suitable statistical tool. Use an online tool for statistics such as the Social Science Statistics calculator.
Urban areas contain urban ecosystems.
Urban ecosystems, like all ecosystems, are composed of biotic components (plants, animals and other forms of life) and abiotic components (soil, water, air, climate and topography).
An urban area is a built-up area with a high population density, buildings and infrastructure.
Urban areas have a dense assemblage of buildings and people located close together for residential, cultural, productive, trade and social purposes; rural areas have relatively low population density and dispersed settlements.
Cities, towns and suburbs are classified as urban areas.
An urban area works as a system.
An urban system is the interconnected system of buildings, microclimate, transport, goods and services, power/energy, water/sewage supply, humans, plants and animals.
In urban systems, consider waste/pollution, urban efficiency, sustainability and resilience.
Application of skills: Create a systems flow diagram representing an urban system.
Urbanization is the population shift from rural to urban areas.
Urbanization involves the process of land use becoming more built-up, industrialized and dominated by dense and continuous human settlement and infrastructures.
Due to rural–urban migration, a greater proportion of the human population now live in urban rather than rural systems, and this proportion is increasing.
Include reasons (push–pull factors, forced versus voluntary) for migration from rural to urban areas and the perceived or real advantages of urban settlements. Most rural–urban migration is an internal migration.
Consider the trend within a country for rural–urban migration, along with deurbanization trends.
Suburbanization is due to the movement of people from dense central urban areas to lower-density peripheral areas.
Suburbanization is sometimes referred to as urban sprawl because lower-density settlements require larger areas of land.
The expansion of urban and suburban systems results in changes to the environment.
Include loss of agricultural land, forests or other natural ecosystems, changes to water quality, river flows and air pollution.
Urban planning helps decide on the best way to use land and buildings.
Urban planning aims to meet the physical, domestic, environmental, commercial, industrial, financial and health needs of all stakeholders in the community.
Modern urban planning may involve considering the sustainability of the urban system.
Consider factors including quality and affordable housing, integrated public transport systems, green spaces, security, education and employment, use of renewable resources, reuse and recycling of waste, energy efficiency, involvement of the community, green buildings. Include one example of sustainable urban planning, such as the Cerdà plan in Barcelona (1860), the Hausmann plan for Paris (1850s), Brasilia (1960), the controversial Forest City in Malaysia, reduction or removal of car use (Copenhagen), EV charging stations (San Francisco), water conservation (Dubai green space irrigated with grey water).
Application of skills: Investigate maps that show the urban development of a city over time.
Ecological urban planning is a more holistic approach that treats the urban system as an ecosystem, understanding the complex relationships between its biotic and abiotic components.
Consider one example from the following list.
• Urban ecology—for example, green spaces, habitats for wildlife, allotments, parks, canals, ponds
• Urban farming—for example, beekeeping, horticulture, aquaculture and city farms
• Biophilic design—for example, living green walls and roofs, water features, natural light
• Resilience planning—for example, vertical farming in cities, building on stilts in flood-prone areas, fail-safe grids
• Regenerative architecture—for example, building skins that scrub the air clean, capturing rainwater that replenishes aquifers, solar panels/wind turbines/biodigesters that export energy
Ecological urban planning will follow principles of urban compactness, mixed land use and social mix practice.
Consider the sustainable advantages of these practices, including reduced urban sprawl, less car dependency, reduced energy consumption, better public transport, increased accessibility and social equality. Avoiding social inequality in access to green areas is a matter of environmental justice.
Societies are developing systems that address urban sustainability by using models such as a circular economy or doughnut economics to promote sustainability within the urban system.
Consider one example of the use of these models in urban development.
Green architecture minimizes harmful effects of construction projects on human health and the environment, and aims to safeguard air, water and earth by choosing environmentally friendly building materials and construction practices.
Green architecture and civil engineering combines new and indigenous knowledge systems, vernacular architecture, bio-based materials and circular construction.
Consider one example of green architecture, for example, bale construction, bottle and plastic construction, 3D printing houses, Arabic wind tower houses (for example, barajeel).
Urban air pollution is caused by inputs from human activities to atmospheric systems, including nitrogen oxides (NOx), sulfur dioxide, carbon monoxide and particulate matter.
Particulate matter is categorized according to size of particle, with PM2.5 being fine particulate matter with a diameter of 2.5 micrometres or less and PM10 being air pollution that is made of larger particulate matter with a diameter of 10 micrometres.
Sources of primary pollutants are both natural and anthropogenic.
Primary pollutants are directly active at the point of emission. Include forest fires, dust and volcanic eruptions as natural sources. Include burning for agricultural and forest clearance, burning of fossil fuels and biomass for energy production, and dust from construction/roads as anthropogenic sources.
Application of skills: Plan an experiment to use an indicator species as a correlate for pollution in the local environment.
Most common air pollutants in the urban environment are either derived directly or indirectly from combustion of fossil fuels.
PM2.5, PM10, carbon monoxide and sulfur dioxide are primary pollutants, and tropospheric ozone, nitric acid and sulfuric acid are secondary pollutants.
A range of different management and intervention strategies can be used to reduce urban air pollution.
Include strategies such as, but not limited to, improved public transportation, infrastructure for cycling, growing trees, natural screens, green walls, compulsory catalytic converters, limited car use and pedestrianized town centres.
NOx and sulfur dioxide react with water and oxygen in the air to produce nitric and sulfuric acid, resulting in acid rain.
Include the chemistry of acid rain formation.
Acid rain has impacts on ecology, humans and buildings.
Effects are: on terrestrial habitats (leaching, toxification of the soil, direct impact on foliage); on freshwater habitats (toxicity due to aluminium solubilization, impacts on fish gills and invertebrate exoskeletons); the corrosion of marble, limestone, steel, paint and other construction materials; on breathing, from nitrate and sulfate particles (tissue damage and lung inflammation from components of PM2.5 and acid deposition).
Management and intervention strategies are used to reduce the impact of sulfur dioxide and NOx on ecosystems and to minimize their effects.
As with other forms of pollution, these pollutants can be managed by altering human activity (for example, using alternative energy sources), controlling at the point of release (for example, scrubbers and catalytic converters) or restoring the damaged systems (for example, healthcare and adding limestone/fertilizer to lakes).
Photochemical smog is formed when sunlight acts on primary pollutants causing their chemical transformation into secondary pollutants.
Include NOx and volatile organic compounds (VOCs) as primary pollutants that are directly emitted. Peroxyacyl nitrates (PANs) and tropospheric ozone are secondary pollutants and the main components of photochemical smog.
Meteorological and topographical factors can intensify processes that cause photochemical smog formation.
Abundant insolation, reduced wind, and temperature inversion are meteorological factors. Consider how temperature inversion occurs and that this will tend to happen in locations that are surrounded by mountains or high buildings.
Application of skills: Use graphs showing diurnal changes in urban air pollutants. Use secondary databases to study change over time in local air quality, using a statistical tool to test the significance of any change.
Direct impacts of tropospheric ozone are both biological and physical.
Damage to plant cuticles and membranes, eye irritation in humans and other mammals, and respiratory illnesses are biological effects. Damage to fabrics and rubber materials are physical effects.
Indirect impacts of tropospheric ozone include societal costs and lost economic output.
Impacts include those upon the healthcare systems and reduced workforces. These impacts may be differential in society, with poorer communities often carrying a larger proportion of these impacts.
22 subtopics
Laws are rules that govern human behaviour and are enforced by social or governmental authority.
Laws are made and enforced by social or governmental authority.
Environmental law refers specifically to the rules about how human beings use and impact natural resources, with the aim of improving social and ecological sustainability.
An environmental law may cover management of natural resources (for example, forests, minerals, fisheries), management of pollution (for example, air, soils, water), protection of biodiversity (for example, wildlife conservation habitats), construction and development projects (for example, EIAs).
Environmental laws can have an important role in addressing and supporting environmental justice, but they can be difficult to approve due to lobbying.
Environmental laws attempt to prevent overexploitation and degradation of natural resources for the short-term interests of a minority above the long-term interests of the common good. Laws can support or ensure ethical behaviour when economic systems incentivize environmental and social harm; however, it can be difficult to get environmental laws passed due to political lobbying of economically powerful stakeholders.
Environmental law is built into existing legal frameworks, but its success can vary from country to country.
Environmental law requires effective enforcement of laws through strong administrative and legal institutions, general acceptance by society, as well as adequate funding to support the environmental protection measures required by law.
Environmental constitutionalism refers to the introduction of environmental rights and obligations into the constitution.
Internationally, there is a growth of environmental constitutionalism as more and more cases are effectively addressed by nations’ constitutions. Climate change issues are increasingly being addressed in this manner. Include an example of a national constitution successfully involved in addressing environmental issues.
Environmental laws can be drafted at the local, national or international level.
Laws made at national or international levels supersede those made at local levels. International laws or bilateral agreements may be created and applied in transboundary environmental issues related to pollution and resource management. Local councils can have laws about recycling and waste disposal; countries create environmental laws for air- and water-quality standards; international environmental agreements exist regarding fisheries and trade in endangered species. Include an example of an environmental law at each scale: local, national and international.
International law provides an essential framework for addressing transboundary issues of pollution and resource management.
There are agreements addressing transboundary pollution (for example, the Association of Southeast Asian Nations (ASEAN) Agreement on Transboundary Haze Pollution) and transboundary resource management (for example, the Food and Agriculture Organization (FAO) International Plan of Action to Prevent, Deter and Eliminate Illegal, Unreported and Unregulated Fishing).
UN conferences produce international conventions (agreements) that are legally binding, and protocols that may become legally binding, to all signatories.
International agreements and protocols can be challenging and slow to develop.
Examples of challenges include the following: the complexity of the agreements, rapidly evolving scientific knowledge, pressures on individual governments from internal stakeholders with differing interests, conflicts between countries over “differentiated responsibilities”, financing commitments of high-income countries towards low-income countries, general geopolitical conflicts, potential economic impact of agreements.
Consider the relative success of the Montreal and Kyoto Protocols and Paris Agreement along with their subsequent amendments and developments.
International agreements can generate institutions or organizations to aid their implementation.
A range of conventions and organizations should be covered in the course, for example, CITES and IUCN.
The application of international environmental law has been examined within international courts and tribunals.
Examples of bodies involved in the development of international environmental law include the International Court of Justice, the International Tribunal for the Law of the Sea, and the European Court of Justice. One of the difficulties faced by international judiciary bodies is how to evaluate appropriate compensation and damages for infringements of environmental law.
There are an increasing number of laws granting legal personhood to natural entities in order to strengthen environmental protection.
Granting legal personhood to natural entities can result in stronger environmental protection and it is similar to the long-established granting of legal personhood to corporations. This links with indigenous knowledge systems that do not recognize the distinction between humans and nature, environmental value systems (anthropocentric and ecocentric) and to a rights-based (deontological) ethics approach.
Both legal and economic strategies can play a role in maintaining sustainable use of the environment.
There are different contributions to sustainable management that can be achieved by the two strategies. There is a challenge in economics of attaching economic value to ecosystem services and their degradation, and the challenge in law of achieving agreement between stakeholders and the enforcement of compliance. The most successful outcomes may come from an integration of the two approaches, for example, laws imposing fines for illegal dumping or oil spills.
Economics studies how humans produce, distribute and consume goods and services, both individually and collectively.
Economics focuses on supply and demand of resources and the outcomes of market interaction.
Environmental economics is economics applied to the environment and environmental issues.
Technocentrics have the perspective that science and technology will enable environmental economics to work within the current economic framework. More ecocentric perspectives tend to value the more innovative approach of ecological economics.
Market failure occurs when the allocation of goods and services by the free market imposes negative impacts on the environment.
For example, a factory that, in the production of goods, causes pollution that creates a net welfare loss on society at no cost to the factory.
When the market fails to prevent negative impacts, the polluter-pays principle may be applied.
The polluter-pays principle means that the costs of stopping, managing and cleaning up the pollution are covered by the polluter. Environmental economics has created solutions such as quotas, fines, taxes, tradeable permits, carbon neutral certification that ensure the polluter pays to limit the burden to society.
“Greenwashing” or “green sheen” is where companies use marketing to give themselves a more environmentally friendly image.
Greenwashing is a form of misinformation when companies or organizations spend time and money on marketing themselves as sustainable or environmentally friendly rather than on changing practices to become sustainable.
For example, oil companies who claim to transition to clean energy.
The tragedy of the commons highlights the problem where property rights are not clearly delineated and no market price is attached to a common good, resulting in overexploitation.
For example, an individual or firm can overexploit a common good despite the detriment to others. This phenomenon highlights a limitation of free market economics in addressing environmental issues. This dilemma can be circumvented, however, through alternative approaches, for example, Ostrom’s shared pastures in Switzerland where the innovative strategy of the local community resolves the issue.
Environmental accounting is the attempt to attach economic value to natural resources and their depletion.
Environmental (or green) accounting is problematic in achieving a consensus value for all stakeholders.
In some cases, economic value can be established by use, but this is not the case for non-use values.
Non-use value may include the intrinsic value of a species, the potential for future use or the value it may have for forthcoming generations. It can be established by estimating through surveys how much people would be willing to pay for a common good, or how much compensation they would be willing to accept in return for the destruction of a common good. For example, the Exxon Valdez oil spill in 1989.
Ecological economics is different from environmental economics in that it views the economy as a subsystem of Earth’s larger biosphere and the social system as being a sub-component of ecology.
The ecological economist perceives the biosphere as a system with inputs of solar energy sustaining natural energy and material resources that enter the economic subsystem which, in turn, produces wastes and an overall loss of low-grade thermal energy from the biosphere. Ecological economics places emphasis on the sustainable use of natural capital, applying the precautionary principle to minimize environmental and social impacts. Ecological economics emphasizes the value of natural capital alongside physical, human and financial capital.
While the economic valuation of ecosystem services is addressed by environmental economics, there is an even greater emphasis in ecological economics.
“Resource depleted” countries pay “resource rich” developing countries to not deplete their natural assets. This could occur when developing countries are at risk of using up their resources to develop economically. For example, forests are seen in ecological economics as having economic value beyond timber value. The ecological services, the aesthetic value for tourism and recreation, and the ethical value are all considered in ecological economics. Countries that have depleted some of their natural assets for economic gain in the past may pay other countries that still have natural assets, such as forests, to not remove them for economic growth. This can create tensions between countries.
Economic growth is the change in the total market value of goods and services in a country over a period and is usually measured as the annual percentage change in GDP.
GDP is the monetary measure of all goods and services produced by a country in a given period of time. Per capita GDP is a more accurate assessment of living standards but does not take into account inequalities in the actual distribution of income.
Economic growth is influenced by supply and demand, and may be perceived as a measure of prosperity.
This approach provides a linear economy that does not usually take into account waste, pollution and issues that lead to environmental degradation.
Economic growth has impacts on environmental welfare.
Economic growth and the resulting increase in incomes can have both positive and negative effects on the environment. It may lead to higher consumption of non-renewable resources, increased pollution levels, global warming and the loss of natural habitats. And it can also provide resources to protect the environment and address environmental problems such as pollution. However, this can be a complex issue, as it raises questions about environmental justice for those who are impacted by increased consumption.
Eco-economic decoupling is the notion of separating economic growth from environmental degradation.
While some countries have claimed some success in decoupling CO2 emissions from economic growth, it seems impossible that there should ever be absolute decoupling. Indefinite growth would seem to require infinite availability of resources, though some argue that technological development can make this possible. Relative decoupling may occur, where resource degradation is at least reduced—although this still allows for some degradation.
Ecological economics supports the need for degrowth, zero growth or slow growth, and advocates planned reduction in consumption and production, particularly in high-income countries.
Balancing the ecological footprint of a country with its biocapacity leads to sustainability, and this is the goal of ecological economics.
Ecological economists support a slow/no/zero growth model.
There are inherent difficulties in dismantling deeply embedded economic systems and objectively measuring social and environmental well-being.
Ecological economists address the extent to which the ecological footprint of a country is sustainably balanced by its biocapacity (and remove the focus on GDP).
The circular economy and doughnut economics models can be seen as applications of ecological economics for sustainability.
The effectiveness of these models in addressing the sustainable activity of a society varies. The circular economy involves product stewardship, in which the responsibility for sustainable management of a product is attributed to the manufacturer, seller and user. There are attempts to quantify the doughnut economics model for different countries and the doughnut model fundamentally attempts to address issues of inequality and injustice.
Ethics is the branch of philosophy that focuses on moral principles and what behaviours are right and wrong.
Students should be exposed to a variety of ethical examples from across the world. Details of these are not required.
Environmental ethics is a branch of ethical philosophy that addresses environmental issues.
This branch of ethics arose in the 1960s and 1970s when environmental issues and awareness became more prevalent. There was a concern that Western ethical traditions focused on interpersonal actions and relationships and were inadequate to address the moral status of non-human or non-living environmental entities.
A variety of ethical frameworks and conflicting ethical values emerge from differing fundamental beliefs concerning the relationship between humans and nature.
If one believes the human species is of no significant difference to the rest of nature, this might lead to a more ecocentric position that all components of nature have intrinsic and equal rights, and ethical judgements can be made on that basis.
If one believes that the human species is part of nature, but has special responsibility of stewardship towards it, that may influence ethical judgements in favour of a compassionate, respectful, good steward.
If one believes that nature is quite separate and is there to serve human needs, then one may be likely to embrace a more extreme anthropocentric or technocentric worldview and simply consider what brings the greatest good to the greatest number of people.
Instrumental value is the usefulness an entity has for humans.
The value may come from providing goods (for example, food and water), services (for example, decomposers processing waste) or opportunities for human development (for example, knowledge or creative inspiration).
Intrinsic value is the value one may attach to something simply for what it is.
For example, non-living objects, such as landscapes, may be valued because they are wild, culturally significant or beautiful. Living organisms may be valued because, like humans, they have parts, processes and behaviours organized to accomplish survival and reproduction, so we should respect their ongoing existence and well-being.
The concepts of instrumental and intrinsic value are not exclusive.
For example, whales may be considered to have intrinsic value from their aesthetic appeal; they may be considered to have instrumental value as a tourist attraction.
An entity has “moral standing” if it is to be morally considered with regard to how we ought to act towards it.
To ask if something has moral standing is to ask if it should be taken into account by others or make a claim on others. Ecocentrists believe that all living things have moral standing because they have intrinsic value. Some ecocentrists would extend this argument to non-living things in nature, such as rivers, rocks, landscapes. For example, Aldo Leopold’s land ethic argues that “a thing is right when it tends to preserve the integrity, stability and beauty of the biotic community. It is wrong when it tends otherwise.” Likewise, one may consider the moral standing of future generations. For example, do humans alive today have obligations towards humans living in the future, irrespective of benefits to humans of today?
There are three major approaches of traditional ethics: virtue ethics, consequentialist (for example, utilitarian) ethics and rights-based (deontological) ethics.
These ethical approaches contrast by focusing on the person’s character (virtues), the consequences of actions or the rights of the entities involved.
Virtue ethics focuses on the character of the person doing the action. It assumes that good people will do good actions and bad people will do bad actions.
It might be judged that respect, compassion and responsibility are virtuous approaches to the natural world.
Consequentialist ethics is the view that the consequences of an action determine the morality of the action.
In consequentialist ethics, actions with good consequences are good actions, and actions with bad consequences are bad actions. Morally good actions are those that result in the greatest common good. The intention of the action does not affect the morality of the action; it is simply a matter of the outcome.
Rights-based ethical systems focus on the actions and whether they conflict with the rights of others. There is debate about what these rights might be.
For example, if one believes that ethical rules come from a religious text and the text states that killing animals is wrong, then one might consider killing animals for food to be ethically incorrect because it conflicts with the rights of the animal.
Some people hold the view that whatever is natural is correct or good. This position is contentious and is described as the “appeal to nature” fallacy.
It is debatable that all that is “natural” is a reliable ethical guide. For example, diseases are natural but not good—is it right to protect mosquitoes despite their spread of disease?
Environmental movements and social justice movements have developed from separate histories but are increasingly seeking common goals of equitable and just societies.
There is a parallel issue of human superiority over nature with other types of exploitation. There are parallels with the rights of disenfranchised social groups, issues of sexism, racism and equity with future generations.
Organised according to the official IBDP curriculum structure.
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