Sahara desert

• Climate


  The weather conditions prevailing in an area in general or over a long period
• The Sahara


  • Largest and hottest desert in the world
  • Covers roughly the same area as the USA
  • About one-quarter is covered by sand desert (ergs)
  • The rest consists of gravel-strewn plains (reg) and areas of barren rocks (hamada)
  • Used to be wetter 1000 years ago
  • Growing even larger, spreading to the south due to more overgrazing and deforestation
• Sahel


  A semi-arid belt of poor, dry soil 300-500 km wide from north to south, stretching from west to east across north Africa between the Sahara Desert and the savanna grasslands
• In the Sahel, average rainfall ranges from 300 to 600 mm per year, and up to 90 per cent of the moisture evaporates
• Drought is natural to the Sahel


  Desertification and land degradation by people have moved the limit for growing crops and grazing animals further south each year
• Countries like Mali now have even less inhabitable land to survive on
• Desertification caused by climate change


  1. Less rainfall

  2. Land degradation

  3. Overgrazing

  4. Overcultivation

  5. Deforestation

  6. More bare ground exposed

  7. More wind erosion

  8. Less topsoil
• Desertification caused by human activity


  1. Population pressure

  2. Migration or starvation

  3. Less nutrients for decomposers to return to soil

  4. Land supports few people and animals
• More bare ground exposed

  More wind erosion and dust storms remove soil
• Less rainfall


  • Less water stored in rock, soil and plants
  • Scrub and desert plants evaporated away
  • High temperatures heat bare ground
  • Crops fail, animals have poorer grazing areas