Introduction: Drylands. Opportunities, challenges, and threats

Hyper-arid, arid, semi-arid and dry-sub-humid climate zones (all of them considered drylands) occupy over 40 % of the Earth’s land surface and are home to more than 2 billion people. Contrary to the popular image of this important set of biomes, drylands are home to 36 % of carbon stores, 30 % of forested areas, 50 % of the world’s livestock, and 44 % of croplands. These figures give an idea of their social, economic, and ecological importance – the focus of the monograph’s first article – and argue for the need to know and understand their functioning and manage human activities in an increasingly changing climate scenario. This is key to enabling their development and preventing their desertification.