Deforestation and Desertification

Deforestation: the removal of forests

The importance of forests (such as the tropical rain forests):

They provide many habitats with a large biodiversity

They absorb large quantities of rain water and release it slowly so maintaining a steady rainfall in local areas. This is useful to farmers

Tree roots hold the soil together and the canopy of leaves reduces the force in rain. If the trees were removed rain may hit the unstable soil with sufficient force to dislodge it causing soil erosion. This eroded soil can block waterways causing flooding

If old trees are burned there is a quick release of all of the carbon dioxide that had been assimilated by that tree over its lifetime – this will slightly increase the level of carbon dioxide in the atmosphere adding to the greenhouse effect

Timber can be obtained from forests in a sustainable way (i.e. without damaging the forest) by:

Replanting to replace removed trees

Selective logging  - removing only some of the trees from a particular area

Coppicing – where trees are not removed but, instead, cut back and allowed to regrow. Doing this in rotation throughout a forest means that there is not complete destruction of one area. In fact coppiced woodland may have a higher biodiversity because the fact that each area is at a different stage of regrowth means that there is a range of different habitats

Desertification: the conversion of fertile land to desert (i.e. where there is insufficient rainfall to support much life – note there are cold deserts)

The land most at risk of desertification is called marginal land; here there is enough water to just sustain life.

Desertification of marginal land can be caused by:

Overgrazing – if plants are unable to regrow quickly enough because of the lack of water. This reduces the plant cover exposing the soil which can then be eroded by the wind and the rain. This erosion is worsened by the trampling of animals

The removal of plants for fuel and building reduces the plant cover and increases erosion

Cultivation of crops – loosens the soil, increasing erosion

Because of the many problems discussed on these pages several laws have been passed, both by the UK and the European parliaments, to attempt to reduce the control air and water quality. It is possible that your exam will include a description of some of these laws and you will be required to comment on their effects.

You do not need to know anything about the laws before the exam 

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