Sustainability (College Board AP® Environmental Science) : Study Guide

Sustainable resource use & environmental sustainability indicators

What is sustainability?

• Sustainability refers to humans using Earth's resources in a way that ensures they are not depleted for future generations

• Sustainable practices aim to balance environmental, social, and economic needs to maintain a healthy planet

• Key principles of sustainability:

  • Conserving natural resources by using them efficiently

  • Reducing waste and pollution through responsible consumption

  • Protecting ecosystems to maintain biodiversity and climate stability

Environmental sustainability indicators

• Environmental indicators help measure progress toward sustainability by tracking changes in ecosystems and resource availability

• These indicators help scientists and policymakers assess environmental health and make informed decisions

Biological diversity (biodiversity)

• Higher biodiversity supports ecosystem stability and resilience

  • A decline in biodiversity is a sign of habitat destruction, pollution, or climate change effects

  • For example, the rapid loss of tropical rainforest species due to deforestation reduces global biodiversity

Food production

• Sustainable food production is necessary to feed a growing human population without degrading land and water resources

• Indicators of food production include:

  • Crop yields (how much food is produced per area)

  • Soil fertility (nutrient levels in soil)

  • Water availability (for irrigation)

• For example, unsustainable farming practices, such as overuse of fertilizers and pesticides, degrade soil quality and reduce long-term food production

Average global surface temperatures & CO₂ concentrations

• Rising global temperatures and increasing CO₂ levels indicate climate change

• Higher CO₂ emissions from fossil fuel burning contribute to global warming

• Monitoring these indicators helps predict climate-related risks such as sea level rise, extreme weather, and droughts

  • For example, the past decade has seen the highest recorded global temperatures, increasing climate-related natural disasters

Human population growth

• A growing human population places greater demand on resources, such as food, water, and energy

• Indicators include:

  • Birth rates and death rates

  • Urbanization trends

  • Resource consumption per capita

• Countries with rapid population growth, such as India and Nigeria, face resource shortages and environmental pressures

Resource depletion

• Overuse of natural resources, such as freshwater, fossil fuels, and forests, leads to long-term shortages

• Unsustainable resource use can result in:

  • Deforestation (loss of forests for agriculture or development)

  • Soil degradation (nutrient loss from over-farming)

  • Water scarcity (depletion of groundwater and freshwater reserves)

The three pillars of sustainability

• Sustainability includes three pillars:

  • Environmental sustainability

  • Social sustainability

  • Economic sustainability

• These pillars are interdependent and must be balanced for overall sustainability

  • For example, a business implementing green practices (environmental) might also improve employee well-being (social) and reduce unnecessary spending (economic) to improve the overall long-term sustainability of the business

Models of sustainability

• Weak sustainability models only show an overlap in the three pillars

  • This type of model does not take into account the importance of the intricate relationships between the pillars

• Strong sustainability models show how the economy is nested within society and how both of these are nested within the natural environment

  • This type of model emphasises the interconnectivity of the three pillars

What is sustainable yield?

Definition of sustainable yield

• Sustainable yield refers to the amount of a renewable resource that can be harvested without depleting it faster than it can naturally regenerate

• This ensures:

  • long-term availability of the resource

  • future generations can continue to use the resource at the same rate

• Applies to forests, fisheries, freshwater supplies, and agricultural crops

Factors affecting sustainable yield

Regeneration rate

• Renewable resources must replenish at a rate equal to or greater than the rate of harvesting

  • For example, fish populations must reproduce fast enough to replace those that are caught

Ecosystem health

• A degraded ecosystem reduces the ability of a resource to regenerate

  • For example, deforestation can lead to soil erosion, making it harder for trees to regrow

Human management practices

• Overexploitation can exceed sustainable limits, causing resource depletion

• Sustainable management includes quotas, protected areas, and seasonal restrictions

Examples of sustainable vs. unsustainable yield

• Sustainable yield:

  • Selective logging in forests, where only mature trees are harvested, allowing younger trees to grow

  • Regulated fishing quotas that ensure fish populations remain stable

• Unsustainable yield:

  • Overfishing that depletes fish stocks faster than they can reproduce

  • Excessive groundwater extraction, leading to water table depletion and land subsidence