Deforestation

• Give 6 causes of deforestation.

  • Settlements
  • Farming
  • Logging
  • Mineral extraction
  • Energy
  • Road building
• Settlements

  The building of settlements caused mass deforestation.

  e.g. Manaus - a city in the middle of the rainforest with a population of 2.2 million people.
• Farming

  As the global demand for meat has increased, large areas have been cleared to make space for cattle farms in the Amazon Basin (pastoral farming).

  Many farmers are clearing land to grow cash crops e.g. soya beans (arable farming).
• Logging

  Tropical rainforests are cut down so valuable trees like mahogany can be accessed and sold for timber to make furniture.

  Other trees are cut down to make paper products.
• Mineral extraction

  The Amazon Basin is rich in natural resources e.g. iron ore, copper, tin, aluminium, manganese and gold.

  This has led to mine development - clears the rainforest.

  e.g. Carajas mine (Brazil) - the world's largest iron ore mine.
• Energy

  Creation of HEP (hydroelectric power) stations in the Amazon Basin has led to large areas of forest being flooded to create reservoirs and dams.
• Road building.

  Construction of access roads for farmers, loggers and miners results in large areas of the rainforest being destroyed.
• What is slash and burn?

  Agricultural practice involving cutting and burning of vegetation to clear land for cultivation.

  
  

  This practice can be done to clear land to make space for shifting cultivation.
• How is shifting cultivation sustainable?

  The ash from slash and burn acts as a fertiliser, adding nutrients to the soil.

  When the soil begins to turn infertile (usually after 3-5 years), the people move on.

  This is a sustainable method of farming.
• What happens to the soil after deforestation?

  Without trees and their roots, the soil is less stable and can easily be washed away (soil erosion).

  This can lead to nutrient-deficient soil, which makes it hard for plants to grow.

  Soil silt can wash into rivers, polluting water supplies and destrying fish and plant habitats.
• How much topsoil is Brazil losing a year as a result of soya farming?

  55 million tonnes.
• What are the negative impacts of deforestation on the atmosphere?

  Rainforests are carbon sinks - they take CO2 from the atmosphere and store it/convert it into oxygen.

  Deforestation releases carbon back into the atmosphere, increasing global dioxide levels.

  CO2 is a greenhouse gas. It traps infrared rays from the sun and heats up Earth's atmosphere.

  This raises average global temperatures, which leads to increased sea temperatures.
• What are the positive impacts of deforestation on the economy?

  Brazil makes $6.9 billion from trade in cattle ranches.

  The mining industry creates jobs e.g. the Buenaventura mining company in Peru employs 3100 people.

  Economic development has brought wealth to many countries surrounding the Amazon.
• EXAM QUESTION - Explain a negative effect of deforestation (3 marks).

  Deforestation of the forest for cattle ranching and soya farming, in the Amazon, removes the top soil layer (1 mark).

  This leads to less nutrients in the soils due to more leaching occurring (1 mark).

  In the long term, this decreases the biodiversity of the rainforest, as plants rely on the nutrients to survive (1 mark).