GCSE Biology revision

Deforestation

Biodiversity and the effect of human interaction on ecosystems

AQA 4.1.1.1

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AQA student objectives

Learning pathway

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ALL 🎯

Identify and describe What is Deforestation?, Why Do People Clear Forests? and Loss of Biodiversity in the context of deforestation.

MOST 🎯🎯

Explain the relationships between What is Deforestation?, Why Do People Clear Forests? and Loss of Biodiversity and how they contribute to deforestation.

SOME 🎯🎯🎯

Apply and analyse knowledge of What is Deforestation?, Why Do People Clear Forests? and Loss of Biodiversity to interpret unfamiliar information about deforestation.

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Key knowledge

Read on screen, then print for Cornell-style active revision.

What is Deforestation?

Deforestation is the large-scale destruction and removal of forests, as dramatically illustrated by the shrinking rainforests of Borneo over the last 65 years.
Forests are often cleared using a method called slash and burn, where vegetation is cut down and set alight to quickly clear large areas of land.

Why Do People Clear Forests?

Forests are cleared to provide agricultural land for growing crops such as rice, palm oil, and biofuels, or for rearing cattle.
Deforestation also occurs to supply timber as a fuel source and to create land for housing and road construction.

Loss of Biodiversity

Deforestation leads to the extinction of species that depend on forest habitats, causing a significant loss of biodiversity.
The destruction of forests also results in the loss of potential new medicines, as many valuable medical compounds are found in tropical rainforest plants and animals.

Deforestation and Carbon Dioxide Levels

Burning trees (combustion) directly releases carbon dioxide into the atmosphere, contributing to the enhanced greenhouse effect.
When dead vegetation decomposes, microorganisms respire and release further carbon dioxide into the atmosphere.
Fewer trees means less photosynthesis, so less carbon dioxide is removed from the atmosphere, causing CO₂ levels to rise.
Cattle farming on deforested land releases methane, another potent greenhouse gas that contributes to global warming.

4. Deforestation and Carbon Dioxide LevelsAQA

Notes

Burning trees (combustion) directly releases carbon dioxide into the atmosphere, contributing to the enhanced greenhouse effect.
When dead vegetation decomposes, microorganisms respire and release further carbon dioxide into the atmosphere.
Fewer trees means less photosynthesis, so less carbon dioxide is removed from the atmosphere, causing CO₂ levels to rise.
Cattle farming on deforested land releases methane, another potent greenhouse gas that contributes to global warming.

Global Warming and Climate Change

Carbon dioxide and methane are greenhouse gases that trap heat in the atmosphere, contributing to the enhanced greenhouse effect and global warming.
The combined effect of increased CO₂ from combustion, decomposition, and reduced photosynthesis means deforestation has a significant impact on global climate change.

5. Global Warming and Climate ChangeAQA

Notes

Carbon dioxide and methane are greenhouse gases that trap heat in the atmosphere, contributing to the enhanced greenhouse effect and global warming.
The combined effect of increased CO₂ from combustion, decomposition, and reduced photosynthesis means deforestation has a significant impact on global climate change.

Soil Erosion and Flooding

When forests are removed, tree roots that bind the soil together are lost, leading to soil erosion and the leaching of minerals, making the soil less fertile.
Rainwater washes eroded soil into rivers, reducing the volume of water rivers can hold and causing flooding in local areas.
Terracing is a technique used in countries like Indonesia to reduce soil erosion on steep or hilly ground, as seen in the rice terraces of Bali.

6. Soil Erosion and FloodingAQA

Notes

When forests are removed, tree roots that bind the soil together are lost, leading to soil erosion and the leaching of minerals, making the soil less fertile.
Rainwater washes eroded soil into rivers, reducing the volume of water rivers can hold and causing flooding in local areas.
Terracing is a technique used in countries like Indonesia to reduce soil erosion on steep or hilly ground, as seen in the rice terraces of Bali.

Arguments For and Against Deforestation

Arguments for deforestation include the economic benefits of using wood for construction, paper, and furniture, as well as creating farmland to grow food and useful products.
Arguments against deforestation include increased global warming, loss of biodiversity, soil erosion leading to flooding, and the extinction of species.
A balanced discussion of deforestation must consider both the economic necessity and the serious environmental consequences.

7. Arguments For and Against DeforestationAQA

Notes

Arguments for deforestation include the economic benefits of using wood for construction, paper, and furniture, as well as creating farmland to grow food and useful products.
Arguments against deforestation include increased global warming, loss of biodiversity, soil erosion leading to flooding, and the extinction of species.
A balanced discussion of deforestation must consider both the economic necessity and the serious environmental consequences.

How Can We Reduce the Impact of Deforestation?

Governments can pass and enforce laws to limit deforestation, though weak enforcement in many countries means illegal clearing continues.
Replanting schemes require that any trees cut down are replaced, helping to restore forest cover over time.
Consumers can choose sustainable wood sources from forests that are responsibly managed and replenished.

8. How Can We Reduce the Impact of Deforestation?AQA

Notes

Governments can pass and enforce laws to limit deforestation, though weak enforcement in many countries means illegal clearing continues.
Replanting schemes require that any trees cut down are replaced, helping to restore forest cover over time.
Consumers can choose sustainable wood sources from forests that are responsibly managed and replenished.

Preserving Rainforests: A Case Study

Preserving rainforests increases biodiversity, reduces atmospheric CO₂, and allows scientists to investigate species as potential sources of new medicines.
Costa Rica is a leading example, having protected its rainforests and benefiting from increased biodiversity, reduced CO₂ levels, and a boost in eco-tourism revenue.

9. Preserving Rainforests: A Case StudyAQA

Notes

Preserving rainforests increases biodiversity, reduces atmospheric CO₂, and allows scientists to investigate species as potential sources of new medicines.
Costa Rica is a leading example, having protected its rainforests and benefiting from increased biodiversity, reduced CO₂ levels, and a boost in eco-tourism revenue.