8 - Cold environments

• Desert fringe areas


  Semi-deserts, semi-arid areas and drylands

  
• Desert fringe areas


  • Rain falls in a fairly predictable pattern, making settled agriculture possible
  • Support greater biodiversity and larger plants than hot deserts
  • Classified as fragile environments

  
• Desertification


  The spread of desert conditions into semi-desert and grassland areas
• Around 1 billion people, or 15% of the world's population, either experience or are threatened by habitable desert fringe areas turning into hot desert areas
• The Sahel is where the human risks created by desertification are greatest, with more than 100 million very poor and vulnerable people living there
• Long-term reduction in rainfall

  Likely cause of desertification in the Sahel
• The African continent has a long history of rainfall fluctuations of varying lengths, including cycles lasting decades
• It is uncertain whether global warming caused by humans will create even greater rainfall deficiencies in the Sahel or other desert fringes
• Some scientists think there is a possibility of rain returning to the Sahel due to global warming, as the heating of oceans adds more water vapour to the atmosphere
• The climatic system is complex and there remains much uncertainty over what will happen to desert fringes in the future
• Population growth


  High fertility, people living longer, and migration leading to more people in fragile desert fringe areas
• Removal of fuel wood

  Wood and vegetation still used for fuel in many countries, leading to unsustainable stripping of vegetation and soil erosion
• Over-cultivation


  Exhaustion of soil fertility due to more crops being planted and aquifers being drained dry, as well as commercial farming of water-hungry cash crops
• Overgrazing


  Too many goats and cattle grazed for too long on one site, preventing vegetation regrowth, due to political boundaries and civil war/instability
• Physical and human causes of desertification are often interlinked
• Protected and prone to wind or water erosion (when it rains), leading to desertification
• Over-cultivation


  Over-cropping land can exhaust the soil's fertility
• As health has improved over time, more of the children born into farming families are surviving infancy, which leads to a rise in small-scale subsistence agriculture. More crops are planted and some aquifers have been drained dry
• Commercial farming worsens this situation. For example, some European companies use large areas of fragile land in Ghana to grow water-hungry cash crops such as jatropha (to make vegetable oil)
• Overgrazing


  If too many goats and cattle are grazed for too long on one site, all the vegetation is eaten and may be unable to regrow
• Nomadic (migratory) groups used to wander freely, following the rain wherever it fell. They would give vegetation a chance to recover. Now they cannot, due to new political boundaries or because large companies have bought up land rights
• Civil war and political instability also force herders to stay too long in fragile places
• Soil erosion


  Fuel wood removal, over-cultivation and overgrazing all lead in turn to soil erosion
• If vegetation has been burned, eaten by cattle or killed by drought, the exposed topsoil becomes baked hard by sunlight
• When it finally arrives, intense rain washes over the soil rather than soaking into the ground, and carries the topsoil away. Once the soil has eroded, it becomes impossible for the vegetation to grow back. A 'tipping point' is reached
• Causes of desertification


  • Overgrazing by cattle
  • More wood used for fuel and shelter
  • Overuse of aquifers
  • Soil erosion
  • Cyclical drought bringing lower and less reliable rainfall
  • Global warming and rising temperatures
  • High fertility among local people
  • Refugees arriving from conflict zones
  • Extreme poverty
• The global issue of climate change plays a role in desertification
• Another contributing factor is that of local pressures, such as: population growth, removal of fuel wood, overgrazing, over-cultivation and soil erosion
• Millions of people fled their land and homes. They were housed in refugee camps, with help from the UN. But refugee camps create new environmental stress wherever they are located and cause desertification to spread
• When people finally return home, further desertification is expected. One charity estimates that each returning family will need 30–40 trees to rebuild their houses and fences. The desert fringes of Sudan do not have enough trees left to support this
• In 2003, nomadic cattle herders and settled farmers began to fight over water supplies and land. Herders were deliberately prevented from reaching water sources by farmers, which led to overgrazing. Once the vegetation was gone, their cattle died. In revenge, some herders chased farmers from their villages, and cut down their crops and trees
• One year out of every five brings drought, crop failure and livestock loss to Sudan
• In Sudan and neighbouring countries, food production has not kept pace with the growing population
• Bunds


  Low stone walls placed in lines across the slope gradient to help prevent soil erosion and slow down the flow of rainwater over the baked ground
• When water pools behind a bund, instead of running fast over the land, it has time to soak into the ground
• The African Union's proposed 'Green Wall' is a plan to plant a wall of trees across the entire Sahel region, running from the Atlantic Ocean in the west, all the way to the Indian Ocean in the east
• In 2019, the project was 15 per cent complete, with most progress taking place in Burkina Faso
• Climate change projections suggest increased aridity may threaten the survival of the trees in the long term
• Appropriate technology


  An alternative way of cooking using efficient stoves that can be made locally and burn much smaller amounts of wood and charcoal
• The Toyola stove in Ghana and the Upesi stove in Kenya are examples of efficient stoves being distributed to rural desert fringe communities by charities