6.11 - Land Use

Land use and habitat destruction

• Land is a limited resource - the more of it humans take, the less is left for other organisms.
• Humans reduce the land available to wildlife by:
  • Building towns and cities
  • Quarrying to extract resources from the ground
  • Farming
  • Dumping waste
• As habitats are taken over, the species that lived there lose their homes, so the number and variety of organisms the area supports falls.

Pollution destroys habitats too

• Habitats are also destroyed by pollution entering rivers, lakes and the sea:
  • Sewage
  • Fertiliser washed off farmland
  • Toxic chemicals from industry
• These can make freshwater and marine habitats unable to support the species that once lived there.

Destroying peat bogs

• A peat bog is an area of acidic, waterlogged ground with too little oxygen for microorganisms to decay dead plants.
• Partly rotted plant material builds up over time as peat, locking away the carbon the plants took in while alive.
• Peat bogs are drained to create farmland, and dug up so the peat can be sold as garden compost or burnt as fuel.

Destroying a bog has two effects:

1. It removes a habitat, reducing the variety of plants, animals and microorganisms that lived there.
2. It lets the stored carbon escape - as oxygen returns to the drained soil, microorganisms decay the peat, and the decay or burning of peat releases carbon dioxide into the atmosphere.

Deforestation

• Deforestation is the large-scale cutting down of forests.
• It's happening fast in tropical regions, where rainforests grow.

Why forests are cleared

• Farming - Clearing land to raise cattle or grow crops such as rice.
• Biofuels - Growing crops for plant-based fuels burned in place of fossil fuels.
• Logging - Harvesting the wood itself for building or for fuel.

The harm deforestation causes

• More carbon dioxide in the atmosphere - Trees that are cut down can no longer photosynthesise and take in carbon dioxide, so more CO₂ stays in the air. Clearing forests by burning also releases the carbon stored in the trees as CO₂.
• Soil erosion and leaching - Removing tree cover exposes the soil, which is washed away by rain and has its minerals leached out.
• Disturbed water cycle - In some forests, losing the trees reduces evapotranspiration, disturbing the water cycle.
• Flooding - Loss of soil and tree cover can lead to flooding.
• Reduced biodiversity - Destroying a rainforest destroys a habitat that held a great variety of species, sharply reducing biodiversity and driving some species towards extinction.