Desertification (SL IB Geography)

• Desertification is:

The process of desert-like conditions spreading into what were previously semi-arid areas, as the quality of soil and its fertility decline over time

• It is possible to argue that human activity and climate change may make many of the natural causes worse

Comparison Between Natural and Human Causes

Natural and human 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 

• Once desertification starts, a pattern follows in a downward spiral that not only affects the physical but also the human aspect
• Soil degradation → soil erosion → reduced agricultural output → malnutrition, famine → migration → conflict → soil degradation etc.
• The consequences of desertification include:
  • Loss of topsoil through exposure to wind and rain
  • Over-exploitation of biodiversity through agricultural practices
  • Vegetation is destroyed, leading to the migration of animals (and people)
  • Water sources are depleted through over-abstraction and/or lack of precipitation, and biodiversity is lost
  • Increased levels of soil salinity through poor irrigation practices 
• Desertification changes the landscape:
  • Reduced sand dune formation as less vegetation to trap loose material
  • Landslides on destabilised slopes where vegetation is removed
  • Vegetation slows wind speeds - as vegetation reduces, wind speeds increase leading to more frequent sandstorms
  • Soil moisture evaporation increases; the soil dries quickly
  • Plant root mat is lost; soil becomes unstable
  • Increased erosion eventually exposes bedrock
  • A combination of higher wind speeds and mobile sediment, transports sand, etc. into other areas, burying vegetation and soil
• Soil and sand encroachment impacts the ecosystem:
  • Land becomes less fertile, impacting flora and fauna as less organic matter is returned to the soil, further reducing growth and biodiversity decreases
  • Distribution of species has/is changing - flora and fauna populations that were present before desertification have either died out or migrated to less degraded areas
  • The process of species adaptation is slow, and inward-moving, already adapted species outcompete native species
  • Desertification destroys soil and vegetation carbon sinks, releasing it back into the atmosphere, enhancing global warming and further changes in climate conditions

Impacts on People in the Desert

• Desertification is a very difficult process to reverse while rainfall remains low
• Halting and reversing desertification means tackling the causes
• There are a variety of possible methods that can be used

Water management

• Contour stones or bunds can be used to increase infiltration
• Earth dams can be used in the wet season to store water
• Drip irrigation can be used to water crops more efficiently 

Education

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

Agroforestry 

• 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

Afforestation

• 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
  • Falling leaves and branches replace nutrients in the soil
  • The trees increase animal and insect activity, which helps improve soil quality

Contour stones or bunds

• 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

Stone contouring on a slope to reduce soil run-off after rainfall

Alternatives futures

• The future for those living in areas of desertification depends on the action taken to mitigate and ameliorate land degradation
• No one plan or action can solve the issue of desertification and this means there are two possible outcomes:
  • Desertification continues (business as usual)
  • Human intervention stops or reverses desertification

Table Showing Possible Futures