To the average person, "desertification" likely conjures up images of sandstorms sweeping across the Sahara. While this is one manifestation, desertification is a global process that persistently reduces the benefits people get from nature -- collectively termed "ecosystem services." This happens as plant cover is destroyed, water resources are over-exploited, soil quality is degraded due to erosion and use of chemicals, and consequently land productivity is irreversibly diminished.
Such processes are taking place all over the globe, not just in deserts.
Desertification is driven by an imbalance between human demand and the supply of benefits by natural systems. Population growth, inappropriate policies, and some aspects of globalization drive unsustainable pressure on drylands.