2.3.3 Desertification | AQA GCSE Geography Revision Notes 2018

Causes of Desertifiication

Desertification is caused by both natural factors and human activities
It can be argued that many of the natural causes may be made worse by human activity and climate change

Comparison Between Natural and Human Causes

Natural causes	Human causes
Soil erosion leads to the loss of nutrients. Plants are unable to establish and grow	Overgrazing means the vegetation has all gone due to the numbers of animals or the land does not have chance to recover
Rainfall patterns have become less predictable leading to drought and any vegetation dying due to lack of water	Over-cultivation leads to all the nutrients being taken up by crops leaving none for future vegetation to grow
Reduced vegetation means that nutrients are not added to the soil through the decomposition of dead organic matter	Deforestation removes shade for the soil and means there are no roots which bind the soil together. This increases soil erosion, whilst decreasing infiltration and interception
Any rain that does fall is often in short, intense bursts, leading to increased surface run off and soil erosion	Population growth puts increased pressure on the land as people raise more animals and grow more crops

causes-of-desertification-edexcel-igcse-geography

Causes of desertification

In areas such as Kenya, both human and natural factors lead to desertification
Grazing patterns and traditional lifestyles mean that:
- Nomadic Masai farmers have been forced to use smaller and smaller areas of land for grazing
  - This results in overgrazing, which removes the vegetation
  - The soil no longer has protection from the wind and rain which leads to soil erosion and desertification
Population growth increases the demand for food and fuelwood
- This leads to over-cultivation and deforestation
- Deforestation:
  - Reduces the amount of nutrients returned to the soil
  - Exposes the soil to wind and rain
- This further increases soil erosion, leading to desertification
In Kenya increasing temperatures and more irregular rainfall are natural causes of desertification
However, these could be the result of the enhanced greenhouse effect (human cause) leading to climate change

Education including:
- Sustainable farming methods including agroforestry and crop rotation, which help to keep the soil healthy
- Family planning to reduce population growth

This combines agriculture with forestry, which means some trees remain, which:
- Decreases deforestation
- Provides shade as well as increasing infiltration and interception, which reduces soil erosion
- Provides organic matter from the trees and adds nutrients to the soil

Tree planting, such as the Great Green Wall across the Sahel, helps to reverse desertification in several ways:
- The roots help to bind the soil together reducing soil erosion
- The canopy offers shade helping to prevent the soil from drying out and also reducing soil erosion from rainfall landing directly on the soil
- Nutrients in the soil are replaced by falling leaves and branches
- The trees increase animal and insect activity which helps improve soil quality

These help to reduce soil erosion by:
- Preventing the soil from being blown or washed away
- Reduce overland flow
- Ensuring that dead organic matter stays in one place and can decompose adding nutrients to the soil
Additionally they increase infiltration of water into the soil

contour-stones

Benefits of contour stones