Continent most affected by desertification

Desertification is defined as the transformation of arable land to desert and drylands. It has a number of natural causes, including climate variation and soil erosion, but also arises as a result of human activities including over-intensive farming, deforestation and even population migration. According to a report published by the UN Economic and Social Council in 2007, around two-thirds of the African continent has been reduced to desert or drylands; around one-third of Africa is affected by moderate to severe desertification.

The report stated that Africa's desert and dryland areas are concentrated in the Sahelian region, the Horn of Africa and the Kalahari in the south and that land degradation affects at least 485 million people (65% of the entire African population).

"Desert" is typically defined as a region that receives 25 cm (10 in) or less rainfall per annum. The wider category of drylands is divided based on a range of factors including levels of precipitation and evapotranspiration: hyper-arid (desert), arid (semi-desert), semi-arid (grassland) and dry sub-humid (rangelands). For the purposes of this report, all dryland types were factored in.