Possibly the most impressive return to a workable environment is the Loess Plateau in China. Centuries of poor management of crops allowed the area of 640,000 square kilometers {250,000 square miles} to be without plant life to keep the fertile topsoil from washing and blowing away. This plateau was alone responsible for the Yellow River in China to have its characteristic yellow color. Yellow loess soil washed down and made the turbid yellow water. Its soil has been termed the "most highly erodible soil" on the planet.

In the time of about one generation of human life, the most inhabited portion of the plateau was turned around. Terracing, replanting, and education has allowed the soil to sustain plant life that holds the soil in place for the rains that formerly washed the soil downstream. Winds no longer blow that topsoil into Beijing, making for unhealthy breathing conditions. Life for the inhabitants has returned to the peaceful agrarian style of those who lived there centuries before.

Of great importance is that work to make the change was done almost exclusively with hard manual labor. Using hand tools to dig the terraces, plant trees and other vegetation, and to re-route some of the minor drainages allowed the transformation. Inhabitants are educated to help keep the plants growing and not allow the plateau to return to its recent past.

Work continues to return more of the plateau to allow the soil to remain stable.

More Info: en.wikipedia.org