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Human Impact on the Environment

Deforestation and overfishing

  • 3 things to know
  • Component 1

Overview

Three reasons why tropical forest is cleared, three further ways of making forestry sustainable and conflict between production and conservation in forestry.

What you need to know

Answer each one before you reveal it.

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Key term

Explain why land often becomes infertile within a few years of clearance.

Key term

Define deforestation.

Key term

Give three environmental consequences of deforestation.

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    Define deforestation.

    Model answer

    The permanent clearance of forest so that the land is put to another use.

  2. 2

    Name three reasons why tropical forest is cleared.

    Model answer

    To sell the timber, to create farmland for cattle or crops such as oil palm and soya, and to reach minerals beneath the ground.

  3. 3

    Give three environmental consequences of deforestation.

    Model answer

    Habitats and the species in them are lost, the exposed soil is eroded and its nutrients leached away, and the carbon held in the trees is released as carbon dioxide.

  4. 4

    Explain why land often becomes infertile within a few years of clearance.

    Model answer

    In a tropical forest most nutrients are held in the living vegetation rather than in the soil, so once the trees are gone there is no leaf fall to replace them, heavy rain leaches the thin nutrient layer away and the roots that held the soil no longer do so.

  5. 5

    Why does deforestation reduce rainfall in a region?

    Model answer

    Much of the rain that falls on a forest is returned to the air by transpiration from the canopy, so removing the trees breaks that cycle and the local climate becomes drier.

  6. 6

    What is coppicing?

    Model answer

    Cutting a broadleaved tree back to a stump from which new shoots grow, so that a crop of poles can be harvested repeatedly without the tree being killed.

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