Using the Earth's resources and sustainable development: distinguish between finite and renewable resources given appropriate information.

The idea

A finite resource is used up faster than it is replaced, so its supply will eventually run out; examples include crude oil, coal, natural gas and metal ores. A renewable resource is replenished at a rate that keeps pace with use, so it need not run out; examples include solar, wind, hydroelectric, tidal and wave power, plus sustainably managed timber. To distinguish them, ask whether the resource is replaced within a human timescale. Given data, look for a falling reserve, a rising extraction cost or a stated formation time of millions of years, which indicate finite. A resource such as fresh water or wood can be renewable only if the rate of use stays below the rate of replacement.

What earns the marks

• Defines finite as a resource being used up faster than it is replaced, so it will eventually run out.
• Defines renewable as a resource replaced at the same rate as it is used, so it will not run out.
• Classifies named examples correctly, such as crude oil, coal and metal ores as finite, and solar, wind and hydroelectric power as renewable.
• Uses the timescale of replacement to justify a classification, for example fossil fuels form over millions of years but are extracted in decades.
• Applies the rate-of-use idea to borderline cases such as timber or fresh water, explaining that they are renewable only when managed sustainably.
• Interprets given information, such as reserve figures or formation times, to decide which category a resource belongs to.

Common mistakes and how to put them right

• Calling any natural material renewable because it comes from the Earth.

  Put it right: Renewable depends on replacement rate, not origin, so coal and oil are finite.

• Treating nuclear fuel as renewable because it does not produce carbon dioxide when used.

  Put it right: Uranium is mined from finite ore deposits, so it is finite.

• Assuming all biomass is automatically renewable.

  Put it right: Wood is renewable only if trees are replanted at least as fast as they are cut down.

Exam tips

• Quote the replacement rate or timescale from the data when justifying each classification.
• Use the words finite and renewable precisely, and avoid the vague term non-renewable unless the question uses it.
• For a table or chart, compare the rate of use with the rate of replacement before writing your conclusion.