Deforestation (AQA GCSE Biology Combined Science): Revision Notes
Deforestation
What is deforestation?
Deforestation means cutting down and clearing forests permanently to make the land available for other uses. This has already happened on a large scale in the UK and other parts of Europe. Today, it continues mainly in tropical areas around the world.
When forests are cleared, the land becomes available for many different purposes. However, this permanent removal of trees causes serious environmental problems that affect the whole planet.
The environmental consequences of deforestation extend far beyond the local area where trees are cut down, creating global impacts on climate and ecosystems.
Main reasons for deforestation
There are three main reasons why people cut down forests on a large scale:
Agriculture and farming
- Land is cleared to grow food crops like rice
- Grassland is created for feeding cattle and livestock
- This provides food for growing populations
Timber and building materials
- Trees are cut down to harvest wood for construction
- Timber is used for building houses and making furniture
- This provides materials for human settlements
Biofuel production
- Crops are grown to make biofuels such as ethanol for cars
- These are used as alternatives to fossil fuels
- This is meant to help reduce carbon emissions from transport
While some reasons for deforestation aim to address environmental concerns (like biofuels reducing fossil fuel use), the overall environmental cost often outweighs these benefits.
Environmental problems caused by deforestation
Deforestation creates serious environmental issues that contribute to climate change:
Increased carbon dioxide in the atmosphere
When trees are burned or cut down, this releases more carbon dioxide into the air. Trees store carbon in their wood, so destroying them puts this carbon back into the atmosphere as CO2. This contributes to global warming.
Reduced carbon dioxide removal
Fewer trees means less photosynthesis happening. Trees normally remove carbon dioxide from the air during photosynthesis and 'lock it up' for many years in their wood. When there are fewer trees, less CO2 is removed from the atmosphere, making climate change worse.
Deforestation has a double impact on climate change: it both increases CO2 emissions when trees are destroyed AND reduces the Earth's natural ability to remove CO2 from the atmosphere.
The role of peat and its destruction
Peat is partly decomposed plant material found in peat bogs and peatland areas. It forms over thousands of years as dead plants break down very slowly in waterlogged conditions.
Peat formation is an extremely slow process - it can take thousands of years to build up significant peat deposits, making their destruction particularly concerning from a conservation perspective.
Why peat matters
- Peat can be used as a fuel in some places
- It's also used to make garden compost
- Peat stores huge amounts of carbon
Problems when peat is destroyed
When peat decays further or is burned as fuel, it releases carbon dioxide into the atmosphere. This adds to global warming. The destruction of peat habitats also reduces biodiversity in these special ecosystems.
Peat destruction is particularly damaging because it releases carbon that has been stored for thousands of years, contributing significantly to greenhouse gas emissions.
Impact on biodiversity
What is biodiversity?
Biodiversity means the variety of all different species living in an ecosystem or on Earth. High biodiversity keeps ecosystems stable and healthy.
Why biodiversity is important
Different species depend on each other for:
- Food and shelter
- Maintaining the physical environment
Our future as a species depends on maintaining good levels of biodiversity around the world.
How deforestation reduces biodiversity
When forests are cleared, many species lose their homes and food sources. For example, when tropical rainforests are replaced with palm oil plantations, there are fewer different types of animals and plants. Studies show that palm oil plantations have much lower biodiversity than the original rainforest - fewer arthropod groups (like beetles and millipedes) survive in the plantations compared to natural forests.
Real-world Example: Palm Oil Plantations vs Rainforest
Research comparing tropical rainforests to palm oil plantations shows dramatic biodiversity loss:
- Original rainforest: High diversity of arthropod groups (beetles, millipedes, etc.)
- Palm oil plantation: Significantly fewer arthropod species survive
- Knock-on effect: Fewer arthropods means less food for larger animals like orangutans and birds
- Result: Entire food webs are disrupted when natural habitats are replaced
This reduction in biodiversity affects other organisms too. When there are fewer arthropod groups, there are also fewer animals like orangutans and birds that depend on them for food.
Species interdependence means that losing even small organisms like insects can have cascading effects throughout entire ecosystems, affecting much larger animals that depend on them.
Summary
Key Points to Remember:
- Deforestation is permanently clearing forests for agriculture, timber, and biofuels
- It increases CO2 in the atmosphere through burning trees and reduces CO2 removal through less photosynthesis
- Peat destruction releases stored carbon and contributes to global warming
- Biodiversity loss happens when natural habitats are replaced with single-crop plantations
- Species interdependence means losing some species affects many others in the ecosystem