Dunes are small hills, mounds or ridges of wind-blown soil material, usually sand, that are formed in both coastal and inland areas. The formation of coastal or inland dunes requires a source of loose sandy material and dry periods during which the sand can be picked up and transported by the wind. Dunes exist independently of any fixed surface feature and can move or drift from one location to another over time. They are the result of natural erosion processes and are natural features of the landscape in many coastal areas and deserts, yet they also can be symptoms of land degradation. Inland dunes are either an expression of aridity or can be indicators of desertification—the result of long-term land degradation in dryland areas.

Coastal dunes are the result of marine erosion in which sand is deposited on the shore by...