Deforestation: causes and impacts Cambridge IGCSE Environmental Management revision
Not started
Learn it
In plain words
A forest takes centuries to grow and a chainsaw crew a few weeks to clear. An area of forest the size of a football pitch is lost every few seconds, and nearly every cause comes down to somebody needing the land or the wood.
9 things to know
- Deforestation is the removal of forest so that the land can be used for something else.
- Logging and timber extraction: trees are cut for building timber, furniture, paper and fuel.
- Farming: subsistence farmers clear small plots to feed their families. Commercial farming clears huge areas for cattle and for crops such as soya and palm oil.
- Roads and settlements are built for growing populations, and roads open the forest to more clearing.
- Extraction of rock, ores and minerals: mines and their roads need land. Hydro-electric power stations flood forest behind their dams.
- Climate change brings drought and wildfires, which kill trees.
- Impacts on living things. Habitats are lost and biodiversity falls. Genetic depletion is the loss of the variety of genes held in the forest's species, including some that could have given new crops and medicines.
- Impacts on soil and water. With no roots to bind it and no leaves to shelter it, soil is eroded, and land can become desert. The soil washes into rivers, causing silting and flooding.
- Impacts on climate. Fewer trees take in less carbon dioxide, and burning them releases it, which adds to global warming. Less water is returned to the air by transpiration, so rainfall patterns change.
Worked example
A hillside forest is cleared. The next year the town in the valley floods for the first time. Explain the link.
- Trees used to intercept the rain and take up water through their roots. Now the rain reaches the ground at once and runs off the surface.
- With no roots to hold it, soil is washed into the river.
- The soil settles on the river bed, which is silting, so the channel is shallower.
- More water arrives faster in a channel that holds less, so the river floods.
Tips and tricks
- Causes and impacts are different lists. Logging and farming are causes. Soil erosion and loss of biodiversity are impacts. Read which one the question wants.
- Do not write "trees give us oxygen" as the main impact. The points that score are habitat loss, soil erosion, flooding and the effect on carbon dioxide.
It lands in your notebook with its questions as flashcards.
Deforestation: causes and impacts: 6 questions and answers
These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.
What is deforestation?
Trees are cleared and not replaced.
Which crop is a major cause of commercial deforestation?
Large areas of forest are cleared for palm oil and soya.
What is genetic depletion?
Genes that could have been useful are gone for good.
Why does deforestation change rainfall patterns?
Much forest rain is recycled through the trees.
How does a hydro-electric power station cause deforestation?
The valley behind the dam goes under water.
Why does a new road through a forest lead to more deforestation than the road itself?Stretch
Clearing spreads outwards from the road.
Quiz
6 questions
Tap an answer and you’ll see straight away whether it’s right, and why.
Worksheet
3 questions, 9 marks. Write your answers on paper, then check them.
Deforestation: causes and impacts
Cambridge IGCSE Environmental Management 0680 · 9 marks · papermunch.org
Name ______________________________ Date ______________
State three causes of deforestation.[3]
Show answerHide answer
Any three: logging and timber extraction; subsistence and commercial farming; roads and settlements; extraction of rock, ores and minerals; hydro-electric power stations; climate change.
Explain how deforestation leads to soil erosion.[3]
Show answerHide answer
The leaves no longer shelter the soil from rain. The roots no longer bind the soil together. Rain and wind remove the loose soil.
Explain two ways in which deforestation adds to global warming.[3]
Show answerHide answer
Fewer trees remove less carbon dioxide from the atmosphere by photosynthesis. Burning or decay of the trees releases carbon dioxide. Carbon dioxide is a greenhouse gas, so more of it increases warming.
Answers: Deforestation: causes and impacts
- 1. Any three: logging and timber extraction; subsistence and commercial farming; roads and settlements; extraction of rock, ores and minerals; hydro-electric power stations; climate change.
- 2. The leaves no longer shelter the soil from rain. The roots no longer bind the soil together. Rain and wind remove the loose soil.
- 3. Fewer trees remove less carbon dioxide from the atmosphere by photosynthesis. Burning or decay of the trees releases carbon dioxide. Carbon dioxide is a greenhouse gas, so more of it increases warming.