What does it actually mean to use a resource sustainably, and how do we measure whether we are?
Topic 5.12 Introduction to Sustainability: define sustainability and sustainable yield, and explain the indicators used to assess whether resource use is sustainable.
A focused answer to APES Topic 5.12, covering sustainability, sustainable yield, the difference between renewable and non-renewable resources, indicators of sustainability (biodiversity, soil, water, productivity), and the link to natural capital, with a worked sustainable-yield calculation.
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What this topic is asking
The College Board (Topic 5.12) wants you to define sustainability and sustainable yield, distinguish renewable from non-renewable resources, and name the indicators used to judge whether resource use is sustainable.
Defining sustainability
Sustainable yield
This is the same idea as maximum sustainable yield in fisheries (Topic 5.8) and applies to forests, groundwater and grazing land.
Renewable versus non-renewable
Indicators of sustainability
Scientists judge sustainability using measurable indicators: biodiversity (declining diversity signals stress), soil health (erosion and fertility), water quality and availability, and primary productivity. Stable or improving indicators suggest sustainable use; declining ones signal degradation. These tie back to ecosystem services (Topic 2.2) and natural capital, the stock of natural resources an economy draws on.
Why this matters
Sustainability is the unifying goal of Unit 5 and much of the course. Every problem in the unit, overfishing, overgrazing, deforestation, aquifer depletion, is unsustainable resource use, and every solution, sustainable agriculture, forestry and aquaculture (Topics 5.15 to 5.17), aims to bring use back within the regeneration rate.
Try this
Q1. Identify whether coal is a renewable or non-renewable resource. [1 point]
- Cue. Non-renewable (it forms only over geological time).
Q2. Explain why harvesting a fishery at its sustainable yield maintains the stock. [2 points]
- Cue. The sustainable yield removes only as many fish as reproduction replaces each year, so the breeding population stays the same size and can keep producing that yield indefinitely.
Exam-style practice questions
Practice questions written in the style of College Board exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
AP 2022 (style)4 marksSection II (FRQ). (a) Define sustainability. (b) Explain what is meant by sustainable yield. (c) Describe one indicator scientists use to assess the sustainability of an ecosystem. (d) Explain the difference between a renewable and a non-renewable resource, with an example of each.Show worked answer →
A 4-point FRQ on sustainability.
(a) Define (1 point): sustainability is using resources in a way that meets present needs without compromising the ability of future generations to meet their own (resources used no faster than they regenerate).
(b) Explain (1 point): sustainable yield is the amount of a renewable resource that can be harvested without reducing the supply for the future, because it is replaced by natural regeneration.
(c) Describe (1 point): an indicator such as biodiversity, soil health/quality, water quality and availability, or primary productivity; a stable or improving indicator suggests sustainable use.
(d) Explain (1 point): a renewable resource regenerates on a human timescale (for example timber, fish, solar energy); a non-renewable resource does not, or only over geological time (for example coal, oil, metal ores).
Markers reward the future-generations definition, harvest replaced by regeneration for sustainable yield, a valid indicator, and the renewable-versus-non-renewable distinction with examples.
AP 2019 (style)1 marksSection I (multiple choice). Which of the following is the best example of a sustainable practice? (A) Harvesting timber faster than the forest can regrow (B) Catching fish at the maximum sustainable yield (C) Pumping groundwater faster than it recharges (D) Clearcutting old-growth forest for farmland. Justify your choice.Show worked answer →
A 1-point MCQ on sustainability. The answer is (B).
Catching fish at the maximum sustainable yield removes only what reproduction replaces, so the stock is maintained indefinitely, which is sustainable. (A), (C) and (D) all use resources faster than they regenerate (or destroy them), so they are unsustainable. The trap is choosing an option that sounds productive; sustainability requires use at or below the regeneration rate.
Related dot points
- Topic 5.11 Ecological Footprints: define the ecological footprint, explain what it measures, and compare footprints between countries and lifestyles.
A focused answer to APES Topic 5.11, covering the ecological footprint, what it measures, the factors that raise or lower it, biocapacity and overshoot, comparison between countries, and how to interpret footprint data, with a worked footprint calculation.
- Topic 5.1 The Tragedy of the Commons: explain how shared, unregulated resources tend to be overexploited, and describe solutions such as regulation and privatisation.
A focused answer to APES Topic 5.1, covering the tragedy of the commons, why individual self-interest depletes shared resources, examples (fisheries, grazing land, the atmosphere), and solutions such as regulation, privatisation and cooperation, with a worked grazing example.
- Topic 5.15 Sustainable Agriculture: describe sustainable farming practices that conserve soil and water and maintain long-term productivity.
A focused answer to APES Topic 5.15, covering sustainable agriculture practices (crop rotation, contour ploughing, terracing, no-till, cover crops, strip cropping, agroforestry, rotational grazing) and how each conserves soil and water and maintains productivity, with a worked erosion-reduction calculation.
- Topic 5.17 Sustainable Forestry: describe sustainable forestry practices that reduce deforestation while still supplying timber.
A focused answer to APES Topic 5.17, covering sustainable forestry practices (selective cutting, reforestation, controlling pests and pathogens, sustainable yield, certification, reducing demand), how they reduce deforestation, and their benefits, with a worked sustainable-harvest calculation.
- Topic 2.2 Ecosystem Services: describe the four categories of ecosystem services and explain how the disruption of ecosystems affects the services they provide.
A focused answer to APES Topic 2.2, covering provisioning, regulating, cultural and supporting ecosystem services, examples of each, their economic value, and how disruption reduces them, with a worked valuation question.
Sources & how we know this
- AP Environmental Science Course and Exam Description — College Board (2020)