Why the world’s drylands need urgent protection
“Broadly speaking, drylands are characterised by a scarcity of water. The United Nations Environment Programme defines them as lands with an aridity index (AI) of less than 0,65. (The AI is the ratio between average annual precipitation and potential evapotranspiration; if the former is less than the latter, the climate is regarded as arid.). It further divides drylands into hyper-arid lands, arid lands, semiarid lands and dry sub-humid lands.
Drylands cover about 41% of the Earth’s land surface, or about 6,1 billion hectares. They are distributed among all continents at tropical and temperate latitudes. Africa has the largest area of drylands (32% of the world’s total), followed by Asia, North America, Oceania, South America and
