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Unlock This CourseIn Causes of Deforestation you saw why forests are cleared: cattle, crops, timber, mining, settlement and dams. This lesson asks what happens next. The spec names four impacts of deforestation: loss of biodiversity, a contribution to climate change, economic development and increased soil erosion. It also wants you to say whether an impact is social, economic or environmental.
Tropical rainforests such as the Amazon basin and the Congo basin are fragile environments. Everything in them is closely linked, so clearing the trees upsets the whole system.
Key terms:
A rainforest has many layers and many habitats, so it holds a huge variety of species. When trees are cut down, animals lose their homes and their food. Some species can only live in one small area of forest. If that area is cleared, they can disappear for ever.
Trees take in carbon dioxide as they grow and store the carbon in their wood. When forest is burned or left to rot, that carbon goes back into the air as carbon dioxide, a greenhouse gas. Fewer trees also means less carbon dioxide taken in each year. Both effects add to the enhanced greenhouse effect.
Cleared land can be used to earn money. Timber can be sold. Cattle ranches and crop farms create jobs and food. Mines, roads and towns bring work and trade. This can raise incomes and help a country to develop.
Trees protect the soil. Leaves and branches slow down heavy rain, and roots hold the soil together. Without trees, rain hits bare ground and washes the soil away. Rivers fill with mud and the land becomes less fertile.
Soil erosion is the impact that links to all the others. Most of the nutrients in a rainforest are in the leaf litter and the top layer of soil. Once the trees are gone, the rain can strip this layer away. Crops then grow poorly, so farmers clear more forest. This is a cycle: clearing leads to erosion, erosion leads to poor soil, and poor soil leads to more clearing.
The spec asks for the social, economic and environmental impacts. Use these three questions:
Indigenous people who live in the forest can lose their homes, food and way of life. New jobs and settlements can also bring people better services, so social effects can be good or bad.
Money from timber, farming and mining is a benefit. The cost comes later, when eroded land earns less and the forest's other products are lost.
Loss of biodiversity, more carbon dioxide in the air and soil erosion are all environmental impacts.
Economic development is the one impact on the list that is a benefit. The other three are harmful. A good answer shows both sides: clearing forest can earn money now but may damage the environment and future income.
Exam answers score higher when each point is explained in steps. Link your ideas with words such as so, which means and therefore.
Question: Explain one impact of deforestation. [3 marks]
Answer: Trees are cut down to make room for cattle ranches (1). Without trees, heavy rain hits bare soil and washes it away, so soil erosion increases (1). The soil loses its nutrients, so crops grow poorly and farmers earn less (1).
(a) State two environmental impacts of deforestation. [2 marks]
(b) Explain how deforestation can lead to economic development. [3 marks]
(c) Explain how deforestation can contribute to climate change. [3 marks]
(a) Loss of biodiversity (1). Increased soil erosion (1).
(b) Cleared land can be used for cattle ranches or crops (1), which creates jobs and food (1). Timber can be sold, so the country earns money (1).
(c) Trees store carbon, and burning or rotting them releases carbon dioxide into the air (1). Carbon dioxide is a greenhouse gas that traps heat (1). Fewer trees means less carbon dioxide is taken in, so more stays in the air (1).
"Explain" needs a reason. Give the impact, then add a "so" or "which means" to show the next step.