Strategies used to manage soil erosion & desertification (Cambridge International IGCSE Geography)

Specification link

This page covers section 10.3.5 of the CIE IGCSE specification .

• 10.3.5 - An evaluation of the strategies and techniques used to manage desertification and soil erosion; including sustainable.

What are soil erosion & desertification

Spec point — An evaluation of the strategies and techniques used to manage desertification and soil erosion; including sustainable.

• Soil erosion is the wearing away of the topsoil by the action of wind or water
• It is a natural process which is made worse by human activities which leave the soil exposed to wind and water

Causes of soil erosion

Deforestation

• Removes the trees reducing interception so the soil is more exposed to the rainfall
• Reduces the amount of roots which reduces infiltration and increases surface runoff
• The bare soil is more exposed to the wind which would have been reduced by tree cover

Overgrazing

• Removes vegetation cover which acts to protect the soil from both wind and water
• More animals trampling the land leads to compaction and increased surface runoff
• This happens more in LEDCs where farmers have less and less land to graze

Over-cultivation

• Land is not left to rest (fallow) between crops and so the fertility of the soil is reduced

Population increase

• More people increase the settlement sizes reducing the areas which can be farmed - increasing over-cultivation and overgrazing
• Increases the demand for food which leads to over-cultivation and overgrazing

Over-abstraction of groundwater

• This leads to the soil moisture content decreasing
• Drier soil is more easily eroded by wind or water

Human-induced climate change

• Changes in climate patterns, increasing floods and increasing droughts all lead to an increase in soil erosion

Salinisation

• Salinisation is also an increasing issue in many semi-arid areas

  • Occurs when high rates of evaporation lead to groundwater being drawn to the surface
  • When the groundwater evaporates salts are left in or on the topsoil
  • These salts make the land toxic to many crops and so the land can no longer be used

Desertification

• Soil erosion may over time lead to desertification
• Desertification is the spread of desert like conditions into semi-arid areas
• It is caused by both natural factors and human activities
• Many of the natural causes may be made worse by human-induced climate change

Natural causes

• Soil erosion leads to the loss of nutrients

  • As a result, plants cannot establish and grow

• Less predictable rainfall leads to drought and vegetation dying

• Intense rainfall leads to increased surface runoff

• Reduced vegetation means that fewer nutrients are added to the soil

Human causes

• Overgrazing reduces the amount of vegetation so the soil is bare and no nutrients are added to the soil

• Over-cultivation means that the crops take up all the remaining nutrients

• Deforestation decreases:

  • the nutrients added to the soil
  • infiltration
  • interception
  • the number of roots which bind the soil

• Population growth increases the pressure on the land increasing the number of animals and crops

Causes of desertification

Exam Hint Remember, desertification is not the expansion of the deserts that already exist. It is when semi-arid ecosystems become desert-like as a result of human activity and unsustainable land use.

Strategies used to manage soil erosion & desertification

Spec point — An evaluation of the strategies and techniques used to manage desertification and soil erosion; including sustainable.

• Halting and reversing soil erosion and desertification means tackling the causes
• There are a variety of political and social responses

Education

• Education, including:

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

Agroforestry

• This combines agriculture with forestry, which means some trees remain
• Increases the variety of plants grown which increases biodiversity

Afforestation

• Tree planting, such as the Great Green Wall across the Sahel

Contour Stones and Terraces

• Stones are laid along the contour lines of the land
• These reduce soil erosion and increase nutrients added to the soil

Use of contour stones to reduce soil erosion

Effectiveness of strategies used to manage soil erosion & desertification

Spec point — An evaluation of the strategies and techniques used to manage desertification and soil erosion; including sustainable.

• The strategies outlined have all proved effective in halting and even reversing soil erosion and desertification

Crop rotation

• Improves soil health and structure
• Breaks the cycle of pests and diseases

Agroforestry

• **Decreases deforestation **because crops are grown alongside the trees
• It 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

Afforestation

• Afforestation is effective because:

  • The roots of trees 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

• Great Green Wall

  • The Great Green Wall project was launched in 2007

  • The project aims to plant an 8 000-kilometre band of trees across 11 Sahel countries

  • By 2024, the Great Green Wall had:

    • Restored 30 million hectares of degraded land
    • Created three million new jobs

  • However, it is only 30% complete and there are only six years left on the project

Contour stones

• These help to reduce soil erosion by:

  • Preventing the soil from being blown or washed away
  • Increasing infiltration of water and reducing overland flow
  • Ensuring that dead organic matter stays in one place and can decompose, adding nutrients to the soil

• In Burkina Faso, Oxfam worked with farmers to improve the traditional stone wall, aiming to increase food production by using bund lines of stones across a slope to stop water and soil from running away

  • This method preserves the topsoil and has improved farming and food production in the village
  • They managed to increase millet, the staple crop in Burkina Faso, production by 50% on average