How does human activity harm the environment, and what can be done about it?
Describe the effects of human activity on the environment, including pollution and habitat loss, and ways to reduce the harm
A scaffolded answer to the N(A)-Level Biology outcome on human impact. How pollution, deforestation and the greenhouse effect harm the environment, and the steps people can take to reduce the damage.
Reviewed by: AI editorial process; not yet individually human-reviewed
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What this dot point is asking
This outcome wants you to describe how human activity harms the environment, including pollution, deforestation and the greenhouse effect, and to suggest ways the harm can be reduced. The marks reward naming a specific human activity, explaining the effect with a clear cause and effect (not just saying it is bad), and giving sensible ways to cut the damage. Linking back to the carbon cycle and food chains strengthens your answers.
The answer
Pollution
Pollution is the release of harmful substances into the environment. Common kinds are:
- Air pollution from burning fuels, including the gases that cause acid rain and the carbon dioxide that adds to global warming.
- Water pollution, for example when fertiliser or sewage runs into rivers and lakes, which can harm fish and other water life.
- Land pollution, such as plastic and other waste that does not rot away and harms wildlife.
Deforestation
Deforestation is cutting down large areas of forest, often for wood, farmland or building. It harms the environment in two main ways. It destroys habitats, so the animals and plants that lived there lose their homes and food, reducing biodiversity (the variety of living things). And it raises carbon dioxide, because fewer trees means less carbon dioxide removed by photosynthesis, and burning the wood releases even more.
The greenhouse effect and global warming
Some gases in the air, such as carbon dioxide, are greenhouse gases: they trap heat from the Sun instead of letting it escape into space. Human activity, especially burning fossil fuels and deforestation, raises the level of carbon dioxide, so more heat is trapped and the Earth becomes warmer. This global warming can melt ice, raise sea levels and change the weather.
Reducing the harm
People can reduce the damage by:
- burning fewer fossil fuels, for example using renewable energy such as solar or wind, and saving electricity;
- reducing, reusing and recycling to cut waste and pollution;
- planting trees (reforestation) to take in carbon dioxide and restore habitats;
- protecting habitats by creating nature reserves and reducing pollution of rivers and the sea.
Examples in context
Example 1. Why plastic in the sea is a problem. Plastic does not rot away, so it builds up in the oceans, where animals can be trapped in it or eat it and be harmed. Reducing, reusing and recycling plastic cuts the amount that reaches the sea. It shows land and water pollution harming food chains.
Example 2. Why countries plant millions of trees. Trees take in carbon dioxide by photosynthesis and provide habitats for wildlife. Large tree-planting projects aim to lower carbon dioxide and restore lost habitats, tackling both global warming and biodiversity loss. It shows a solution that works through the carbon cycle.
Try this
Q1. Name one greenhouse gas. [1 mark]
- Cue. Carbon dioxide (also accept methane).
Q2. State one harmful effect of deforestation. [1 mark]
- Cue. It destroys habitats and reduces biodiversity (or it raises carbon dioxide in the air).
Q3. Explain how using renewable energy instead of fossil fuels helps the environment. [2 marks]
- Cue. Renewable energy releases little or no carbon dioxide, so less heat is trapped, which reduces global warming and air pollution.
Exam-style practice questions
Practice questions written in the style of SEAB exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Original4 marksExplain how burning fossil fuels can lead to global warming.Show worked answer →
Burning fossil fuels (coal, oil and gas) releases carbon dioxide into the air. Carbon dioxide is a greenhouse gas, which means it traps heat from the Sun in the atmosphere instead of letting it escape into space.
As more fossil fuels are burned, the level of carbon dioxide in the air rises, so more heat is trapped. This makes the Earth warmer overall, which is global warming. It can melt ice, raise sea levels and change weather patterns.
What markers reward: burning fossil fuels releasing carbon dioxide, carbon dioxide being a greenhouse gas that traps heat, and more of it meaning more heat trapped and a warmer Earth. Saying carbon dioxide makes a hole in the ozone layer is a different problem and is not correct here.
Original4 marksDescribe two harmful effects of cutting down large areas of forest (deforestation).Show worked answer →
Effect 1: it destroys habitats. The animals and plants that lived in the forest lose their homes and food, so many of them die or have to move, which reduces biodiversity (the variety of living things).
Effect 2: it raises carbon dioxide in the air. Trees remove carbon dioxide by photosynthesis, so cutting them down means less is removed; and if the wood is burned, even more carbon dioxide is released. This adds to global warming.
What markers reward: two clear effects, such as loss of habitat and biodiversity, and more carbon dioxide in the air (less photosynthesis and/or burning), each briefly explained. Just saying it is bad for animals without explaining how scores only partly.
Related dot points
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