1. Safriel, U. et al. Dryland systems in The Millennium Ecosystem Assessment Series, Ecosystems and Human Well-being: Current State and Trends, Volume 1 (eds. Hassan, R., Scholes, R. & Ash, N.) 623–662 (Island Press, 2005).
2. Schimel, D. S. Drylands in the Earth system. Science 327, 418–419 (2010).
3. Middleton, N. J. & Thomas, D. S. G. World Atlas of Desertification, 2 nd Edition (Arnold, 1997).
4. Prăvălie, R. Drylands extent and environmental issues. A global approach. Earth-Sci. Rev. 161, 259–278 (2016).
5. Trabucco, A. & Zomer, R. J. Global Aridity Index (Global-Aridity) and Global Potential Evapo-Transpiration (Global-PET) Geospatial Database. CGIAR Consortium for Spatial Information. http://www.cgiar-csi.org (2009).