Deforestation | tutor2u Geography
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Deforestation

  • Levels: AS, A Level
  • Exam boards: AQA, Edexcel, OCR, IB

The removal of long-established woodland is known as deforestation (the opposite – replanting a forest is ‘reforestation’ while establishing a new forest where one has not existed for a significant period of time is ‘afforestation’).

Deforestation can be conducted deliberately – usually for economic reasons – or by natural environmental processes.

Causes of Natural Process Deforestation

  • Volcanism: volcanic blast effects, lava flows, pyroclastic clouds and ash falls can all cause forest areas to be destroyed. (see the region to the west of Mt St. Helen’s after its eruption in 1980
  • Landslides: mass movement of hillsides can destroy forested slopes. Ironically, it is often human deforestation of upper slopes and plateaux that can contribute to landslides.
  • Drought: significant forest loss occurs at the margins of deserts when periodic rainfall becomes less intense and prolonged to the extent that trees are unable to adapt and survive.
  • Rising sea levels: forests on low-lying land close to the sea may be damaged irreversibly by periodic inundation by the sea, or by the seeping of saltwater into groundwater supplies as sea levels rise.
  • Increasing disease: some diseases attack particular tree species – such as Dutch Elm disease. In western Canada, conifers are being attacked by the pine bark beetle which is able to extend its range northwards due to milder winter temperatures.
  • Wildfires: increasing summer droughts and shorter winters are extending the range of wildfires in much of SW Australia, Mediterranean Europe and California which can devastate vast areas of forest.

Causes of Human Process Deforestation

  • Fuelwood: for much of human history, and still in many parts of rural Africa, trees are harvested for fuelwood. With growing populations the denudation may occur faster than regrowth.
  • Commercial logging: the exploitation of trees for timber, construction materials and paper products is one of the biggest causes of deforestation in Canada, Scandinavia and the Amazon Basin.
  • Land clearance: the removal of forest to create additional farmland for grazing or crop production, large-scale industrial activity such as strip-mining or, in some cases, urban expansion.
  • Acid rain damage: the production of sulphur and nitrous oxides by power stations and vehicle exhausts can combine with water droplets in the lower atmosphere to produce acid rain. Much forest in central Europe has been severely damaged by acid rain emanating from industrial regions further west.

Key Consequences of Deforestation

  • Loss of biodiversity of tree species.
  • Loss of habitat for wildlife.
  • Reduced transpiration causing local rainfall patterns to change to more episodic, intense rainfall events.
  • Greater soil drying as there is less shading material.
  • Increased soil erosion with more intense raindrop impact and less tree material to hold soil in place.
  • Increased flooding as faster surface run-off with more soil content adds to river levels in a shorter lag-time.
  • Reduced absorption of carbon dioxide from the atmosphere with consequences for climate change.
  • Reduced biomass to add to nutrient levels in the soil – particularly leaf litter.
  • Reduced visual attractiveness of landscape: people typically value water, forests and varying relief. Loss of forest can reduce tourism and leisure attractiveness of an area.
  • Short-term economic gain for local communities. (But potential for ‘boom and bust’ if trees are not replaced at an equivalent rate to that of exploitation.)
  • Increasing the range of potential habitats (coniferous forest supports only a narrow range of habitats; clearing and replacing with a variety of alternative habitats can increase species diversity.)
Could blockchain save the Amazon rainforest?

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