🌿 High biodiversity
Many species live in the ecosystem. If one species dies out, others can take its place as food or shelter. The ecosystem carries on working.
Biodiversity and Human Impact » Biodiversity and Waste Management
What you'll learn this session
Study time: 30 minutes
AQA spec: 4.7.3.1, 4.7.3.2
- What biodiversity is and why a high level of it keeps ecosystems stable
- Why the future of humans depends on biodiversity
- Why a growing population and a higher standard of living mean more resources used and more waste
- How pollution of water, air and land happens, and how it reduces biodiversity
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Unlock This CourseWhat is biodiversity?
Walk through a flower-filled meadow and you might see dozens of different plants, insects, birds and small mammals. Walk across a car park and you might see almost nothing alive. The meadow has a much higher biodiversity.
Biodiversity is the variety of all the different species of organisms on Earth, or within an ecosystem. So it can describe two scales: all the species on the whole planet, or just the species living in one place, such as a single pond, hedgerow or woodland.
The key word is species. A field with a million plants of one type of grass is full of living things, but it has very low biodiversity because there is only one species. A smaller patch with 30 different species has a much higher biodiversity.
Key terms:
- Biodiversity: the variety of all the different species of organisms on Earth, or within an ecosystem.
- Pollution: harmful substances released into the water, air or land.
- Sewage: waste water and waste from homes and buildings that is carried away in drains.
- Landfill: burying waste in the ground.
Why high biodiversity makes ecosystems stable
A great biodiversity ensures the stability of ecosystems. It does this by reducing the dependence of one species on another for food, shelter and the maintenance of the physical environment.
⚠ Low biodiversity
Few species live in the ecosystem, so each one is depended on heavily. If one species is lost, other species that relied on it can be lost too.
Think of a predator that eats only one type of prey. If that prey disappears, the predator has nothing to eat and may die out. A predator that can eat five different types of prey is much safer, because losing one type still leaves four.
The same idea works for shelter. An animal that can only nest in one type of tree is in trouble if that tree is lost. An animal that can use many types of tree can cope.
Species also help to maintain the physical environment. For example, plants hold soil in place and help to keep water in the ground. If many different plants do this job, the loss of one of them does not matter so much.
Common mistakes
Biodiversity is not just the number of animals. It is the variety of different species. Another mistake is to say that "more species means no species can die". High biodiversity does not stop species dying out. It reduces how much the other species depend on each one.
Why humans need biodiversity
The future of the human species on Earth relies on us maintaining a good level of biodiversity. We are part of ecosystems and we depend on other species and on stable ecosystems for the things we need to live.
Many human activities are reducing biodiversity. Only recently have measures been taken to try to stop this reduction. You will meet those measures in the lesson called Maintaining Biodiversity. The way land use, deforestation and global warming affect biodiversity is covered in the lesson called Land Use, Deforestation and Global Warming. This lesson looks at how waste and pollution cause harm.
More people, more resources, more waste
Rapid growth in the human population and an increase in the standard of living mean that increasingly more resources are used and more waste is produced. There are more people, and each person tends to use more.
Unless waste and chemical materials are properly handled, more pollution will be caused. Waste is not a problem if it is dealt with safely. It becomes a problem when it leaks, is dumped or is burned without care.
Worked example
Question: Explain why a higher standard of living can increase pollution. [2 marks]
Answer: A higher standard of living means people use more resources, so more waste is produced (1). If the waste is not handled properly, more pollution is caused (1).
Three places pollution can occur
💧 In water
From sewage, fertiliser or toxic chemicals.
☁ In air
From smoke and acidic gases.
🌍 On land
From landfill and from toxic chemicals.
Notice that toxic chemicals appear in two lists. Toxic chemicals can pollute water and they can pollute land, so make sure you can say both.
Pollution of the air by acidic gases from burning fuels links to your Chemistry course, where you may study atmospheric pollutants from fuels.
Worked example
Question: A farmer spreads too much fertiliser and some is washed into a stream. Which type of pollution is this? [1 mark]
Answer: Pollution of water (1), because fertiliser is one of the sources of water pollution.
How pollution reduces biodiversity
Pollution kills plants and animals, which can reduce biodiversity. When a species is killed off in an area, the variety of species there falls.
When biodiversity falls, the ecosystem becomes less stable. Fewer species are left, so the ones that remain depend on each other more. This is why pollution matters both for the species killed and for those that survive.
Common mistakes
Do not just write that pollution is "bad for the environment". In an exam, say that pollution kills plants and animals, and that this reduces biodiversity.
Exam-style question
(a) State what is meant by biodiversity. [1 mark]
(b) Explain why a pond with high biodiversity is more stable than a pond with low biodiversity. [2 marks]
(c) Name two sources of pollution in water. [2 marks]
(d) Explain how pollution can reduce biodiversity. [2 marks]
Model answer
(a) The variety of all the different species of organisms on Earth, or within an ecosystem (1).
(b) Species depend less on one another for food, shelter or the physical environment (1), so the loss of one species does not harm the others as much (1).
(c) Any two from: sewage (1), fertiliser (1), toxic chemicals (1).
(d) Pollution kills plants and animals (1), so the number of different species falls (1).
Exam tip
In (b), say what the species depend on one another for. Marks are given for food, shelter or the physical environment, not for the word "stable" alone.