The subject principles that are the focus in all topics should be used to develop a holistic understanding of sustainability and the circular economy. Examples should be taken from throughout the areas of study to gain an understanding of the interconnected nature of environmental problems and solutions to these problems. Students should consider sustainability on local, national and global scales.
3.6.1 Dynamic equilibria
Students should understand the role of dynamic equilibria in natural and human systems and how this understanding may be used to develop sustainable human societies.
3.6.1.1 Negative feedback mechanisms which resist change
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Global Climate Change eg: - increased temperatures causing increased cloud cover and a higher albedo
- increased carbon dioxide levels leading to greater photosynthesis and carbon sequestration.
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Hydrological cycle eg: increased evaporation leading to increased precipitation. | |
Population regulation eg: homeostatic population regulation caused by density-dependent factors. | |
3.6.1.2 Positive feedback mechanisms which increase change
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Global Climate Change. | Increased temperatures may increase the following features involved in positive feedback mechanisms:- melting of permafrost
- ocean acidification
- decline of albedo
- methane hydrate releases
- forest and peat fires
- formation of cirrus clouds
- soil decomposition rates.
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3.6.1.3 Equilibrium tipping points which lead to new equilibria
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Global Climate Change. | These are natural processes that become self-sustaining due to human activities eg forest fires, methane hydrate releases, permafrost melting. |
3.6.1.4 Diverse systems are more likely to be resistant to change
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High diversity natural systems: - coral reefs, tropical rainforests
- low diversity human systems
- agroecosystems.
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3.6.2 Energy
Students should understand that future energy will be affected by changing availability, the development of new technologies, economic factors and environmental concerns.
Natural systems are driven by energy in very different ways from anthropogenic systems.
The principles of natural systems being driven by renewable, low energy-density processes at low temperatures should be contrasted with human systems to consider how copying natural systems could help the development of a sustainable society.
3.6.2.1 Natural processes are driven by renewable energy, especially solar power
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Hydrological cycle. Carbon cycle. Nitrogen cycle. Atmospheric circulation. Thermohaline circulation. | The use of renewable energy resources in natural processes provides long-term sustainability in contrast to anthropogenic processes reliant on non-renewable energy resources. |
3.6.2.2 Natural processes use low energy-density resources
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All the natural processes driven by solar energy are driven by low energy-density resources. | Natural processes that rely on low 'energy-density solar energy' capture the energy at a low energy density. It may be used in natural processes at a low energy density or may be converted into other energy forms with a higher energy-density which may be applied more easily to human activities. |
3.6.2.3 Most natural processes occur at low temperatures
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Eg:- photosynthesis produces carbohydrates
- enzymes reduce the activation energy of reactions
- nitrogen fixation.
| Students should compare the natural systems that use low temperatures with human systems that use high temperatures eg biological fixation of nitrogen compared with the Haber process using fossil fuels. |
3.6.2.4 Carbon footprints and sustainable development
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The concept of carbon footprints introduced in the Physical Environment should be re-considered in evaluating the contribution of mimicking natural energy systems to achieve sustainability. | |
3.6.3 Material cycles
The use of mineral resources should be re-considered to evaluate how an understanding of natural cyclical processes may increase the sustainability of human systems.
3.6.3.1 Linear human systems lead to resource depletion and waste generation
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The use of fossil fuels | The reliance on non-renewable energy resources cannot be sustainable. Inefficient use and use when renewable resources are available accelerates depletion rates. |
The use of mineral resources | Human use of minerals often involves dispersal after use or produces mixtures from which separation is difficult. These make recovery and re-use difficult so sustainable exploitation is reduced. |
3.6.3.2 Natural processes often link together in sequences that create cycles, with the waste products of one process being the raw materials for other processes
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Natural processes use a relatively small number of elements, which build into monomers. These build to produce a wide range of polymers eg carbohydrates, proteins. | Students should consider how the use and re-use of abundant, simple raw materials in natural cycles results in sustainability and how this principle may be applied to human systems. |
3.6.3.3 Natural waste products are either non-toxic or do not build up to cause toxicity
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The molecules produced by natural processes are biodegradable and can be broken down to non-toxic products that are the raw materials for other natural processes. | Students should consider how the low toxicity of the wastes of natural systems and the natural processes that process them minimise environmental problems and provide sustainable supplies. |
3.6.4 The circular economy
The circular economy should be evaluated as a possible development strategy that engages in a benign way with natural systems. These should be considered in terms of the development of sustainable lifestyles using circular economy principles.
Students should reconsider the sustainability of natural processes studied throughout the course, especially those emphasised in sections Dynamic equilibria , Energy and Material cycles , to evaluate the ways human society may become sustainable.
3.6.4.1 The application of the principles of the circular economy to the development of sustainable lifestyles
Students should select examples studied throughout the course to illustrate the possible inclusion of natural principles into the circular economy.
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Cycling of materials | Biogeochemical cycles and recycling. |
Energy derived from renewable sources | Solar and non-solar renewable energy in natural and human systems. |
Human activities should support ecosystems. | The inclusion of ecosystem conservation in human planning eg agriculture, forestry, fisheries, energy use, waste management. |
Separation of technical and biological materials. | Separation of biodegradable wastes from other materials eg metals to enable reuse. |
How diverse systems are more resistant to change. | Diverse ecosystems and diverse technical systems eg the use of a range of renewable energy resources. |
Connected systems where the waste product of one process is the raw material for another process. | Natural biogeochemical cycles compared with pollution caused by human wastes. |
Design of products for end of life reuse. | Design to enable re-use of components or materials eg vehicles, domestic equipment. |
Optimum production rather than maximum production. | Consideration of natural system where over-production supports processes upon which the system relies eg plant products which support pollinators, seed dispersal agents and microbes such as decomposers and mycorrhizal fungi. This can be contrasted with agroecosystems which aim for maximum harvested yields. |
Technologies to design new products and improve system effectiveness. | Improved designs to increase energy use, reduce material use and enable dismantling for re-use |
Students must evaluate the extent to which the principles of the circular economy can be applied to human activities to develop sustainable lifestyles in the following activities: | |
Land uses that support natural ecosystems | The inclusion of living organisms into urban landscapes to conserve wildlife and improve quality of life. |
Water supplies | Water conservation and catchment management. |
Mineral supplies | Increasing reserves by exploiting low-grade ores. |
Waste management | Reduced use, reuse, repurposing, recycling. |
Pollution control | A move from post-production treatment to non-release by changes in technology eg from internal combustion engines to fuel cells. |
Energy supplies | The use of renewable energy resources and the development of low-temperature manufacturing processes. |
Food production. | The inclusion of natural processes in nutrient supply, pest control and soil maintenance. |
3.6.4.2 Biocapacity and ecological footprints: a comparison of the factors controlling the impact of different ecological footprints on biocapacity
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Review of different regions of the world, including use of the WWF Living Planet Report, Living Planet Index and ecological footprint calculations. | Students should consider how the strategies that can be implemented to achieve sustainability could be used to reduce ecological footprints and maintain or enhance biocapacity in different regions of the world. |
3.6.5 Opportunities for skills development and independent thinking
Mathematical skill number | Opportunities for skills development and independent thinking |
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MS 1.7 | Students could intepret a scatter graph to compare human development index with the environmental footprint of different countries. |
MS 1.8 | Students could compare per capita, national and global data for the use of a range of resources. |
MS 2.5 | Students could use logarithmic data when comparing rates of change in human populations. |
MS 3.2 | Students could use data from graphs to calculate rates of change in human populations. |
MS 3.4 | Students could calculate rates of carbon sequestration from data on changes in mean tree biomass and forest area. |
MS 3.5 | Students could interpret computer models on population growth to estimate dates when global population will reach a particular size. |
MS 3.6 | Students could use data on carbon emissions, sequestration/removal rates and atmospheric CO2 concentrations and estimate future temperature change. |
Working scientifically
Practical skill number | Opportunities for skills development and independent thinking |
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PS 1.2 | Students could analyse data on fossil fuel use and hydrocarbon reserves to assess future supply problems. |
PS 1.4 | Students could identify the impacts of fossil fuel use and plan a monitoring programme to assess the impacts of changing to renewable energy resources. |
PS 3.1 | Students could interpret graphs on population growth, resource consumption, biodiversity loss and pollution emissions within the context of sustainable lifestyles. |
PS 3.2 | Students could analyse data on resource reserves to consider margins of error and the problems of basing decisions on uncertain data. |