Impacts of Desertification (AQA A Level Geography)

• 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. 

Impacts on ecosystems

• Ecosystems are affected by desertification in a number of ways:
  • 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  

Flow chart showing links between climate change, biodiversity loss and desertification

• 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 - 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
  • Species adaptation is slow and native species are outcompeted by inward, already-adapted species
  • Desertification destroys soil and vegetation carbon sinks, releasing it back into the atmosphere, enhancing global warming and further changes in climate conditions

• 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

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

• Desertification is a very difficult process to reverse while rainfall remains low
• However, there is some evidence that if rainfall increases, the fragile environment can start to recover 
• Solutions need to be realistic and help people to cope with the natural changes to prevent further degradation
• That means using accessible and appropriate technology
• Intermediate technology is a middle ground between low and high-tech farming methods
• Drought cannot be prevented, although there is experimentation on cloud seeding using silver iodide pellets to bring about rainstorms
• The best methods involve water storage schemes and increasing community preparedness
• Some solutions include:
  • Crop rotation and careful selection of crops
  • Fertilisers, High Yield Varieties (HYV) and Genetically Modified (GM) crops can:
    • Increase the yield and reduce the amount of land cultivated
    • HYV and GM crops tend to be drought and pest resistant
  • Solar and wind energy 
    • Cultivation of fast-growing species for fuelwood, and use of alternative (renewable) forms of energy for cooking
  • Working as a community, and education on agricultural management
    • Working with local people, to help them understand the issues, and how to manage them simply
    • Low-cost, simple and manageable solutions that help people to help themselves to survive and remain where they are
  • Building barriers (shelter beds) to wind and water erosion
    • Terracing and contour-plowing on steep slopes reduces soil erosion through runoff down the slope
    • Diguettes are lines of stones laid along the contours of sloping farmland to catch rain and allow the water to seep into the soil. Prevents the soil from being blown or washed away and ensures that dead organic matter stays in one place and can decompose adding nutrients to the soil
    • Zai pits (planting pockets or micro basins) are small holes, filled with minimal organic material. Rainfall water is caught and concentrated close to the plant roots where it is needed
    • Building semi-circular ‘demi-loons’ (half moon) shapes and planting seedlings within them reduces runoff and helps keep more water in the soil – and improves productivity

Diguettes or stone contouring on a slope to reduce soil run-off after rainfall

• Reforestation/afforestation
  • Planting trees and perennial shrubs to bind the soil, such as the Great Green Wall across the Sahel
  • This provides a protective cover that reduces soil erosion and retains soil moisture
  • 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 
• Changing farming practices to agroforestry crop plots
  • This combines agriculture with forestry, which means some trees remain, which:
    • Decreases deforestation
    • Provides shade as well as increases infiltration and interception, which reduces soil erosion
    • Provides organic matter from the trees and adds nutrients to the soil
• Management of water resources
  • Drip irrigation can be used to water crops more efficiently 
  • Earth dams can be used in the wet season to store water
  • Small dams in streams or existing gullies can reduce the speed of water and reduce soil erosion from runoff when it rains
  • Water spreading weirs, gently spread available water further across the land, reducing soil erosion
  • Building stone and cement weirs across valleys in a series along the length of a valley can control and hold back flow, but allow some ‘overflow’ downstream to the next weir
  • Overall, the speed of flow is reduced, allowing alluvium to be deposited, infiltration rates to increase, and the water table to rise = more cultivable land and food security increases
  • They are not cheap ($US400-20000 per ha), but are cheaper than a dam,
  • Also, aid organisations provide loans and the increased crop yields, help towards paying this back