Desertification (DP IB Geography)

Causes of Desertification

• 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

• 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 

Consequences of Desertification

• Desertification is a form of land degradation

• Land degradation indirectly affects about 350 million people in the developing world

• Land degradation occurs through changes in soil character, wind erosion, or water shortages (droughts), which leaves the land unproductive or lost

• Soils in arid and semi-arid regions are potentially very fertile, as there is insufficient water to leach minerals from the soil

• These soils have high pH values and intense evaporation at the surface results in the capillary rise of soil moisture and minerals; this is salinisation 

• When irrigation water is added to land and allowed to evaporate, this has the effect of increasing salinisation

• This process has made a lot of land in the hot deserts infertile

• Increased soil salinity restricts most plant growth and is also phytotoxic when there are high concentrations of sodium in the soil

• Soil erosion is the washing away or blowing away of topsoil, which greatly reduces the fertility of the remaining soil

• This is a natural process made worse through human activity

• There is a link between soil erosion and desertification

• 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

• Changes to hot desert ecosystems and landscapes have a knock-on effect on human populations

Social impacts

• Dust clouds (from soil erosion) affect air quality and health

• Reduction in clean water supplies creates hygiene issues and increases water-borne diseases

• People are forced to migrate, with many people—young men in particular—leaving to work in cities and towns

• This adds pressure on already limited urban resources

• Disputes occur over land between herdsmen and farmers

• Food shortages lead to malnutrition and famine, e.g. in Ethiopia

• This can also result in increased movement to refugee camps, e.g. Syria to Jordan

Economic impacts

• As the land becomes unproductive, farm income falls

• This leads to widespread poverty and an increased reliance on overseas aid

• Desertification also reduces vegetative productivity, leading to long-term declines in agricultural yields, livestock yields, plant standing biomass, and plant biodiversity

• Reduced agricultural exports, increased dependency on government grants

• People and communities suffer the loss of income, further reducing the ability to produce food, which affects the economy of the country

Climate change and desertification

• By 2050, temperatures in the world’s drylands could rise by 2 to 5°C, accelerating and increasing desertification impacts

• Precipitation rates will decrease; moving semi-arid areas into arid regions

• Extreme weather events are likely to become more frequent

• Increased migration to already overcrowded cities

• Less productive soils will lead to rural areas becoming less viable, forcing more people to migrate further afield, This adds pressure on other countries to provide food, water and shelter when they themselves may be struggling

• Some may stay and adapt by using soil conservation strategies or changing agricultural practices

Management of Desertification

• 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

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