page_title: Drylands
section_title: Dry and sub-humid lands
hierarchical_section_title: Drylands / The four sub-types / Dry and sub-humid lands
caption_attribution_description: English: Spiny Forest, Madagascar
context_page_description: Drylands are defined by a scarcity of water. Drylands are zones where precipitation is balanced by evaporation from surfaces and by transpiration by plants. The United Nations Environment Program defines drylands as tropical and temperate areas with an aridity index of less than 0.65. One can classify drylands into four sub-types:
  dry sub-humid lands
  semi-arid lands
  arid lands
  hyper-arid lands
  Some authorities regard hyper-arid lands as deserts although a number of the world's deserts include both hyper-arid and arid climate zones. The UNCCD excludes hyper-arid zones from its definition of drylands.
  Drylands cover 41.3% of the earth's land surface, including 15% of Latin America, 66% of Africa, 40% of Asia and 24% of Europe. There is a significantly greater proportion of drylands in developing countries, and the proportion increases with aridity: almost 100% of all hyper-arid lands are in the developing world. Nevertheless, the United States, Australia and several countries in Southern Europe also contain significant dryland areas.
context_section_description: Countries like Burkina Faso, Botswana, Iraq, Kazakhstan, Turkmenistan and the Republic of Moldova, are 99% covered in areas of dry and sub-humid lands. The biodiversity of dry and sub-humid lands allow them to adapt to the unpredictable rainfall patterns, that leads to floods and droughts. These areas produce the vast amount the world's crops and livestock. Even further than producing the vast majority of crops in the world, it is also significant because it includes many different biomes. 
     Biomes include:
  Grassland
  Savannahs
  Mediterranean climate
caption: Spiny forest, Madagascar
exif: {"Image Copyright": ""}