Drylands make up 47% of the land surface of the Earth. Home to rich biological diversity, they are also central to the livelihoods of almost 2 billion people. Drylands ecosystems receive very erratic rainfall, and as a result are very fragile. Biodiversity in these ecosystems is under threat from a variety of human activities. The transformation of habitats for human use, mostly agricultural, and increases in over-exploitation, including overgrazing, has led to the degradation of up to 20% of drylands ecosystems - with stark results: desertification and drought, the endangerment of 2,311 species, the loss of over 40 billion dollars a year in lost agricultural production and the resulting rise of social, economic, and political tensions. Poverty has forced populations who are dependent on natural resources to overexploit already marginal lands in order to sustain their livelihoods.