What does it mean when the author says that Forest precede mankind and deserts follow.

The author of  "The Ailing Planet: the Green Movement's Role" describes the Earth as suffering from numerous maladies, because of the rampant misuse of her resources. Man in order to ensure his survival has mercilessly cut own trees. This uncontrolled deforestation has resulted in lush forested land being turned into barren stretches. Thus, the land which once was lush and green has now become lifeless like a desert.