Deforestation (Cambridge O Level Biology)

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Deforestation

Deforestation

  • Deforestation is the clearing of trees (usually on a large scale)
  • If trees are replaced by replanting it can be a sustainable practice
  • Generally, the trees are being cleared for the land to be used in a different way (for building, grazing for cattle, planting of monocultures such as palm oil plantations etc) and therefore it is not sustainable
  • As the amount of the Earth’s surface covered by trees decreases, it causes increasingly negative effects on the environment and is a particularly severe example of habitat destruction
  • Undesirable effects of deforestation include:
    • Extinction of species
    • Loss of soil
    • Flooding
    • Increase of carbon dioxide in the atmosphere

deforestation by burning

An example of an area of deforestation caused by deliberate burning of the forest for agriculture

Jami Dwyer, Public domain, via Wikimedia Commons

Consequences of Deforestation Table

Effect Consequence
Extinction/loss of biodiversity

Forest habitats, especially tropical rainforests, have a huge range of biodiversity and as habitat is destroyed it causes the loss of large numbers of plant and animal species

Many of these species are only found in these areas and therefore will become extinct

Soil erosion

Tree roots help to stabilise the soil, preventing it from being eroded by rain

Trees will usually take up nutrients and minerals from the soil through their roots

Without trees, nutrients and minerals will remain unused in the soil so will be washed away into rivers and lakes by rain (leaching)

This loss of soil nutrients is permanent and makes it very difficult for forest trees to regrow, even if the land is not cultivated with crop plants or grass for cattle

Flooding Without trees the topsoil will be loose and unstable so will be easily washed away by rain, increasing the risk of flash flooding and landslides
Increased carbon dioxide in the atmosphere

Trees carry out photosynthesis during which they take in carbon dioxide and release oxygen

The removal of significant numbers of trees means less carbon dioxide is being removed from the atmosphere (and less oxygen released)

When areas of land in forests are cleared for land use, the trees are often burned as opposed to being cut down. This releases carbon dioxide (it is an example of combustion), further increasing carbon dioxide levels in the atmosphere and contributing to global warming

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Phil

Author: Phil

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Phil has a BSc in Biochemistry from the University of Birmingham, followed by an MBA from Manchester Business School. He has 15 years of teaching and tutoring experience, teaching Biology in schools before becoming director of a growing tuition agency. He has also examined Biology for one of the leading UK exam boards. Phil has a particular passion for empowering students to overcome their fear of numbers in a scientific context.