Sustainability practice questions.

A community harvests timber from a forest each year at a rate equal to the forest's annual growth. What is the community using?

• The natural income of the forest
• The natural capital of the forest, which is being run down
• A non-renewable resource that cannot be replaced
• The carrying capacity of the forest for timber

Answer: The natural income of the forest

Natural income is the yield a stock produces that can be taken without reducing the stock itself, so harvesting at the growth rate leaves the natural capital intact. Cutting faster than the growth rate would begin to consume the capital.

A country's ecological footprint per capita is larger than its biocapacity per capita. This means that

• the country has more productive land than its people need
• the country's population has stopped growing
• the country's carrying capacity has been permanently destroyed
• the country's demand on ecosystems exceeds its own supply

Answer: the country's demand on ecosystems exceeds its own supply

The footprint measures the area of land and water needed to supply a population and absorb its waste, while biocapacity measures the productive area actually available. A deficit means the shortfall is met from elsewhere or from depleting stocks, not that capacity has been destroyed.

Which resource is best described as replenishable natural capital rather than renewable natural capital?

• A cod stock managed with an annual catch quota
• Groundwater in a slowly recharging aquifer
• A plantation of fast-growing eucalyptus
• Wind driving an offshore turbine array

Answer: Groundwater in a slowly recharging aquifer

Replenishable natural capital is non-living but is restored by natural processes over time, such as groundwater or the ozone layer, whereas renewable natural capital is living or a continuous flow. The distinction matters because replenishable stocks recover far more slowly than the rate at which they are usually abstracted.

What is the main purpose of carrying out an environmental impact assessment before a large dam is approved?

• To guarantee that any project affecting a protected species will be refused outright
• To calculate the financial return the dam will make over its lifetime
• To predict the likely environmental effects before the decision is taken
• To monitor pollution levels once the dam has begun operating

Answer: To predict the likely environmental effects before the decision is taken

An EIA establishes a baseline, predicts the effects of the proposal and sets out mitigation, so that the decision maker is informed before consent is given. It does not itself refuse projects, and monitoring after construction is a separate stage.

A city has an ecological footprint of 5.2 gha per person, while the biologically productive land inside its own boundary amounts to 0.1 gha per person. This comparison shows that

• the city runs an ecological deficit and depends on productive land elsewhere
• the city has a biocapacity surplus that it exports to the surrounding region
• the footprint must have been measured in the wrong unit, since footprints are given in tonnes
• the city's per-capita resource use must be below the global average

Answer: the city runs an ecological deficit and depends on productive land elsewhere

The footprint is the area demanded to supply resources and absorb waste, while biocapacity is the area available; where demand exceeds local supply the shortfall is imported through trade and global sinks. The unit is always area (gha), never mass.

The environmental impact assessment for a proposed port begins by measuring water quality, sediment movement and species abundance at the site before any construction starts. This stage of the assessment is the

• baseline study
• scoping exercise
• environmental audit
• post-project monitoring

Answer: baseline study

Without a baseline there is nothing against which later change can be measured, so the assessment could never attribute an impact to the port. Scoping decides which impacts are worth studying, and an audit examines an operation that is already running.