Notes · Environmental ScienceUK · A-Levels

Sustainability

This chapter draws the course together around the idea of living within environmental limits. It covers the meaning of sustainability and sustainable development, the principles of sustainable resource use and the circular economy, the measurement of sustainability through ecological and carbon footprints, and the strategies for more sustainable living at every scale, throughout weighing environmental protection against economic and social needs.

4 sections~13 min reading time3 competenciesLevel Foundation 1 · Standard 1 · Advanced 2

T·151515 / 16

Exam profile

AO1 · Describe sustainability, sustainable development, sustainable resource use and how sustainability is measuredAO2 · Calculate and interpret carbon and ecological footprints and percentage changesAO3 · Evaluate sustainability strategies and their environmental, economic and social trade-offs

Operators:describeexplaincalculateanalyseevaluatediscuss

basic level

AS-Level expects you to describe sustainability, renewable and non-renewable resources, and the main ways of living more sustainably.

higher level

The full A-Level requires you to calculate and interpret footprints and to evaluate sustainability strategies and their trade-offs.

Depth

Text

Contents · 4 sections

Sustainability

Sustainability and sustainable development#

FoundationAQA 7447 3.6

The three pillars of sustainability

Fig. 1Sustainable development lies where the environmental, economic and social pillars overlap.

Sustainability means using resources and the environment in a way that can continue indefinitely, without depleting the resources or degrading the systems on which future use depends. The most widely used definition, from the Brundtland report, describes sustainable development as development that meets the needs of the present without compromising the ability of future generations to meet their own needs. This introduces the crucial idea of intergenerational responsibility: sustainability is fundamentally about not passing on a depleted and damaged world.

Sustainable development is usually described as resting on three pillars: environmental, economic and social. It must be environmentally sustainable, staying within the limits of what ecosystems can provide and absorb; economically sustainable, able to support livelihoods and development; and socially sustainable, fair and meeting people's needs. True sustainability lies where all three overlap, and the tension between them, the fact that economic development can conflict with environmental protection, is the source of most of the trade-offs met throughout the course.

Underlying sustainability is the idea of environmental limits: the Earth has a finite capacity to supply resources and to absorb wastes, and living beyond that capacity, drawing down natural capital, cannot continue. This is the concept of carrying capacity applied to the human population and its demands. When humanity uses resources faster than they are renewed and produces wastes faster than they are absorbed, it is in overshoot, living off capital rather than income, which by definition cannot last.

Sustainability is therefore both a scientific and a social idea. The science sets the limits, how much a fishery can yield, how much carbon the atmosphere can absorb, how fast a soil forms, while the choices about how to live within them involve economics, politics and values. Recognising that sustainability requires balancing environmental limits with economic and social needs, and that this balance involves genuine trade-offs rather than easy answers, is the mature understanding the examination rewards in the synoptic questions this chapter supports.

Worked example

Applying the definition of sustainability

A community harvests firewood from a woodland faster than the trees regrow. Explain why this is unsustainable and what a sustainable rate would be.

Compare use and renewal
Wood is being removed faster than the woodland regrows, so the stock of trees is falling year on year.
Apply the definition
This depletes the resource, so it cannot continue and it reduces what future generations inherit, making it unsustainable.
State the sustainable rate
A sustainable rate would harvest no more wood each year than the woodland regrows, so the stock stays constant, living off the income not the capital.

Result: Harvesting faster than regrowth depletes the woodland and is unsustainable; sustainability requires harvesting no more than regrows.

Typical mistakes

Treating sustainability as purely environmental and ignoring the economic and social pillars.
Confusing living off income (sustainable, using the renewable flow) with living off capital (unsustainable, depleting the stock).

Active revision

Explain, using the idea of environmental limits, why a rate of resource use that exceeds the rate of renewal cannot be sustainable.

Active recall

Recall the key points — then reveal.

Sources: AQA AS and A-level Environmental Science (7447) specification (AQA) · GCE AS and A level subject content (Department for Education)

Sustainable use of resources and the circular economy#

StandardAQA 7447 3.6

The circular economy

Fig. 2A circular economy keeps materials in use through reuse and recycling, in contrast to the linear take-make-dispose model.

Resources are sustainable to different degrees. Renewable resources, replenished by natural processes, can be used sustainably provided the rate of use does not exceed the rate of renewal; non-renewable resources, existing as a finite stock, cannot be used sustainably in a strict sense, so the aim is to make them last, to use them efficiently and to recover and recycle them. Low-density renewable resources, such as sunlight and wind, are effectively inexhaustible but require large areas and infrastructure to harvest. Judging a resource use as sustainable therefore depends on the type of resource and the rate and manner of its use.

The dominant pattern of resource use has been linear: raw materials are extracted, made into products, used, and thrown away as waste, a take-make-dispose model that depletes resources at one end and produces pollution at the other. This linear model is inherently unsustainable because it treats resources as unlimited and the environment as a bottomless sink. The alternative is the circular economy, which keeps materials in use for as long as possible by designing products to last, reusing and repairing them, and recycling their materials back into new products, so that waste is minimised and resources are conserved.

The circular economy applies the waste hierarchy and the principle of closing loops at the scale of the whole economy. By designing out waste, keeping products and materials in use, and regenerating natural systems, it reduces both the demand for new raw materials and the pollution from disposal, cutting the impacts met throughout the course, from mining to landfill to greenhouse-gas emissions. It connects directly to the recycling of metals in the minerals chapter and the waste hierarchy in the pollution chapter, showing how those ideas add up to a systemic change.

Moving towards sustainable resource use combines several principles: reduce consumption where possible, use renewable resources within their renewal rate, use non-renewable resources efficiently and recover them, and close material loops. None of these alone is sufficient, and there are limits, not everything can be recycled and some consumption is necessary, but together they define what sustainable resource use means in practice and set up the individual and collective strategies considered later in the chapter.

Worked example

Applying circular-economy thinking

A company makes electronic devices that are cheap to buy but hard to repair and are discarded after a few years. Suggest how it could make its products more consistent with a circular economy.

Design to last and repair
Design the devices to be durable and easy to repair and upgrade, so they stay in use longer and less material is needed.
Reuse and recover
Offer take-back and refurbishment so devices are reused, and design them so their materials can be recovered and recycled at end of life.
Effect
Keeping products and materials in use reduces the demand for new raw materials and cuts the waste sent to disposal, closing the loop.

Result: Designing for durability, repair, reuse and recycling keeps materials in use, reducing raw-material demand and waste.

Typical mistakes

Calling any renewable resource automatically sustainable; it is only sustainable if used no faster than it is renewed.
Assuming everything can be recycled indefinitely; recycling has limits and uses energy, so reducing consumption comes first.

Active revision

Explain how moving from a linear to a circular economy would reduce both the demand for raw materials and the amount of waste produced.

Active recall

Recall the key points — then reveal.

Sources: AQA AS and A-level Environmental Science (7447) specification (AQA) · GCE AS and A level subject content (Department for Education)

Measuring sustainability: ecological and carbon footprints#

AdvancedAQA 7447 3.6

A carbon footprint by source

Fig. 3A personal carbon footprint broken down by source (illustrative proportions): identifying the largest sources guides where to cut emissions.

To manage sustainability it must be measured, and two related measures are widely used. The ecological footprint is the area of productive land and sea needed to supply the resources a person, activity or population uses and to absorb the wastes they produce, usually expressed in global hectares. It can be compared with the biocapacity, the productive area actually available; when the footprint exceeds the biocapacity, the population is in overshoot, using more than the Earth can sustainably provide, which by definition cannot continue.

The carbon footprint is a more focused measure: the total greenhouse-gas emissions caused by a person, product, activity or organisation, expressed as a mass of carbon-dioxide equivalent, so that gases of different global warming potential can be added together. It can be broken down by source, typically home energy, transport, food and the goods and services consumed, which makes it a practical tool for identifying where the largest emissions come from and where reductions would be most effective. Calculating and interpreting a carbon footprint, including expressing a reduction as a percentage, is a standard quantitative task.

These measures make the abstract idea of environmental limits concrete and comparable. They show that lifestyles and countries differ enormously in their demands, that the wealthiest use far more than a fair share of the Earth's capacity, and that current global consumption exceeds what the planet can sustainably provide. They also allow the effect of a change, switching energy source, changing diet, travelling differently, to be quantified, turning sustainability from a slogan into something that can be measured and tracked.

Like all indicators, footprints have limitations that should be acknowledged in evaluation. They rest on assumptions and averages and cannot capture everything, for example some pollution and biodiversity loss are hard to express as an area, and the figures are estimates. Nonetheless they are valuable because they aggregate diverse impacts into a single comparable measure and reveal overshoot, and being able to calculate, interpret and critique a footprint is exactly the applied, evaluative skill this chapter develops.

\text{percentage reduction} = \frac{\text{footprint before} - \text{footprint after}}{\text{footprint before}} \times 100

Reduction in footprint

Used to express how much an action cuts a carbon or ecological footprint; a higher percentage means a greater reduction.

Worked example

Calculating a reduction in carbon footprint

A household has a carbon footprint of 15 tonnes of carbon-dioxide equivalent per year. After improving insulation and switching to a heat pump it falls to 9 tonnes. Calculate the percentage reduction.

Find the reduction
Reduction = $15 - 9 = 6$ tonnes of carbon-dioxide equivalent.
Express as a percentage
$\dfrac{6}{15} \times 100$ .
$\frac{6}{15} \times 100 = 40\%$
Interpret
The measures cut the footprint by 40%, showing that home energy is a large, reducible source for this household.

Result: The household cuts its carbon footprint by 40%.

Typical mistakes

Confusing the ecological footprint (an area) with the carbon footprint (a mass of greenhouse gases).
Treating a footprint as an exact figure rather than an estimate based on assumptions and averages.

Active revision

A person's carbon footprint is 12 tonnes of carbon-dioxide equivalent per year. After switching to renewable electricity and cutting car use it falls to 8 tonnes. Calculate the percentage reduction.

Active recall

Recall the key points — then reveal.

Sources: AQA AS and A-level Environmental Science (7447) specification (AQA) · GCE AS and A level subject content (Department for Education)

Strategies for sustainable living and their evaluation#

AdvancedAQA 7447 3.6

Strategies for sustainability at every scale

Fig. 4Sustainability is pursued at every scale, using legislation, economic incentives and education.

Sustainability can be pursued at every scale, and the strategies at each reinforce one another. At the individual and household level, using energy and water efficiently, reducing and reusing and recycling, choosing low-carbon transport, and eating a more sustainable, less resource-intensive diet all reduce a person's footprint. At the community and national level, decisions about energy supply, transport systems, building standards, farming and waste shape the footprint of the whole society, often more powerfully than individual choices, because they change the options available to everyone.

At the global level, sustainability requires international cooperation, because many environmental problems, climate change, ozone depletion, fisheries, biodiversity, cross borders and cannot be solved by one country alone. International agreements set shared targets and rules, and where they are widely adopted and enforced they can be effective, as the Montreal Protocol showed for ozone. Such agreements are difficult to negotiate and enforce, and progress on climate has been slower, which makes the comparison between them a valuable subject for evaluation.

Achieving sustainable behaviour uses a mix of tools. Legislation and standards require or forbid certain actions; economic instruments, such as taxes on pollution, subsidies for clean technology and the polluter-pays principle, change the incentives so that the sustainable choice becomes the cheaper one; and education and information change what people know and value, enabling informed choices. Because each tool has strengths and limits, they are usually combined: a standard sets a floor, a tax gives an incentive to do better, and education builds the support that makes both durable.

Evaluating sustainability strategies means weighing their environmental benefit against their economic and social costs and their practicality, the same balancing of the three pillars introduced at the start of the chapter. A measure that is environmentally ideal may be too costly or socially unfair, while a cheap measure may achieve little; and there are genuine trade-offs between development and environmental protection, especially between richer and poorer countries. The strongest answers reach a reasoned overall judgement, recognise the trade-offs, and draw synoptically on the whole course, treating sustainability as the framework that ties together climate, resources, pollution and conservation.

Worked example

Evaluating a policy tool

A government introduces a tax on carbon emissions to encourage a shift to low-carbon energy. Evaluate this strategy.

Environmental benefit
By making high-carbon energy more expensive, the tax gives an incentive to use less and to switch to low-carbon sources, reducing emissions (the polluter-pays principle).
Economic and social costs
It raises the cost of energy, which can fall hardest on poorer households and on energy-intensive industry, so it may be socially unfair unless the revenue is used to offset this.
Judgement
A carbon tax can be effective if set high enough and enforced, but it works best combined with standards, investment in alternatives and measures to protect vulnerable groups, balancing the three pillars.

Result: A carbon tax can effectively cut emissions but must be designed to manage its social costs, illustrating the trade-offs of sustainability.

Typical mistakes

Focusing only on individual actions and overlooking the greater effect of national and global decisions.
Presenting a strategy as costless; sustainability involves genuine trade-offs between the environmental, economic and social pillars.

Active revision

Evaluate the use of a carbon tax as a strategy for reducing a country's greenhouse-gas emissions, considering its effectiveness and its social effects.

Active recall

Recall the key points — then reveal.

Sources: AQA AS and A-level Environmental Science (7447) specification (AQA) · GCE AS and A level subject content (Department for Education)

References & sources

Sources

AQA

AQA AS and A-level Environmental Science (7447) specification

Department for Education

GCE AS and A level subject content

Sustainability

4 sections~13 min reading time3 competenciesLevel Foundation 1 · Standard 1 · Advanced 2

Sustainability

Key points

Applying the definition of sustainability

Key points

Applying circular-economy thinking

Key points

Calculating a reduction in carbon footprint

Key points

Evaluating a policy tool

Sources

Sustainability

Key points

Applying the definition of sustainability

Key points

Applying circular-economy thinking

Key points

Calculating a reduction in carbon footprint

Key points

Evaluating a policy tool

Sources