Global Change in Aridlands
Our global change research is motivated by the fact that aridlands span diverse ecosystems on all continents, comprising over 40% of Earth’s terrestrial surface (i.e., 6.1 Bn ha), 44% of all cultivation, and one-third of the human population. Aridlands are also where impacts from climate change are expected to be relatively severe (e.g., California, Mexico, sub-Saharan Africa) compared to other global regions. Unfortunately, aridlands, especially aridland soils, remain vastly understudied relative to their area.
 Here, we define aridlands using the United Nations Environment Program Aridity Index (AI), where AI = Mean Annual Precipitation / Mean Annual Potential Evapotranspiration, and according to hyperarid (AI < 0.03, 7.5%), arid (0.03 – 0.2, 12.1%), semiarid (0.2 – 0.5, 17.7%), and dry sub-humid (0.5 – 0.65, 9.9%) climate classes (AI values, % global land area).