Drylands encompass land areas characterized by a mean annual precipitation to mean annual potential evapotranspiration ratio (known as the aridity index) below 0.65. The aridity index defines four distinct dryland subtypes: hyper-arid (aridity index < 0.05), arid (0.05 ?aridity index < 0.20), semi-arid (0.20 ?aridity index < 0.50) and dry sub-humid …