Hello, I want to know what is meant by unsustainable in the following context from a book called Microbiology: a very short introduction.   Soils exposed by deforestation lack the physical structure, chemical composition, and indigenous populations of microbes needed to cultivate consecutive harvests of cereals and other food crops. Intensive grazing of cattle on deforested land is similarly unsustainable. Even in areas where soils are exceedingly rich, crop productivity falls