3))Hot desert-adaptation human activity challenge case study

• Hadley cell


  • Global-scale tropical atmospheric circulation
  • Warm air rises along the equator (intertropical convergence zone)
  • Warm air contains more water vapour than cold air
  • As the warm air rises and cools, water vapour condenses and forms rain
  • The air masses move towards the tropics and sink back towards Earth as part of the Hadley convection cells
  • The sinking air is dry, resulting in arid climates
  • The sinking air becomes compressed and heats up, absorbing any moisture from the clouds and creating clear skies
  • High pressure systems are associated with dry weather and clear skies
• Latitude is not the only factor that determines climate
• Winds


  • Winds that blow from continental interiors are dry
  • Regions affected by winds blowing from a water mass are more humid
• Continentality


  • The further away from the oceans, the less water there is in the atmosphere
• Relief


  • Mountain ranges may cut off areas from local rain patterns in a phenomenon known as rain-shadow effect
  • As a warm air mass meets a mountain, it is pushed upwards to higher altitudes to produce rain or showers, and when it passes over a mountain it cools down
  • It goes down the other side of a mountain, gaining back its warm mass which sucks up moisture as it travels downwards
  • The removal of moisture results in a dry region devoid of further precipitation
• Cold ocean currents


  • Air blowing over a cold ocean current, e.g. the Benguela current off Namibia, cools down and causes offshore rain and fogs
  • Once the air moves over land it is warmed up and any water evaporates
• Plant adaptation in hot deserts

  • Long roots to reach underground water
  • Thick trunks
  • Waxy leaves to avoid moisture loss
  • Spikes to deter consumer species
  • Seeds that can lie dormant for years and germinate very quickly after rain
  • Lichen extracts minerals from rocks
• Organisms in hot deserts/ plant adaptation

  • Get drinking water from their food
  • Live in burrows to protect from sun
  • Have little urine production
  • Have light-coloured skins/furs to reflect sunlight
  • Have reduced sweating
• Primary consumers


  • They tend to be small
  • There are many of them
  • They are herbivores (vegetarians)
• Secondary consumers


  Organisms that eat primary consumers
• Secondary consumers


  They are meat eaters (carnivores)
• There are relatively few large mammals in deserts because most are not capable of storing sufficient water and withstanding the heat
• Deserts often provide little shelter from the sun for large animals
• In ecosystems with low species diversity, competition for limited resources can be intense
• Earth house in Taos

  • Wooden frame
  • Covered with clay to keep it cool in the daytime heat
  • Small windows to reduce sunlight and keep temperatures low inside
  • Light colour reflects sunlight
• Benefits from the River Colorado's water

  • Enables irrigation and farming activities
  • Brings water to cities throughout the Western Desert area
  • Provides an income as it is used to attract tourists
  • Hydroelectric power plants installed at water dams provide electricity
• Water security


  A society's capacity to have enough water of sufficient quality for survival and to carry out different productive activities
• Problems caused by Colorado river management

  1. Ecosystems are disturbed as the dams prevent silt and sand to be carried by the river

  2. Silt heats up the water-cooler water changes the ecosystem

  3. Sandbanks which have been home to many species in the lower course, disappear

  4. Economic activities disappear as the river course changes
• Under a 1944 treaty established between the U.S. and Mexican governments, Mexico was allotted a guaranteed annual quantity of water
• Drought and rising temperatures

  Have accelerated evaporation from reservoirs
• Melted snowpack faster


  Rivers run dry earlier
• Tropical-desert constree affect Que in