Is there a "breaking point" in the number of animals and land needed?

Is there such a thing as too many animals put in an area to try to revitalize it? How large of an area is needed to keep the animals moving? If you keep a large number of animals in a space, there will eventually be a reversal, causing what we all think we know about livestock and farmland. So what's the correlation between number of animals and amount of land needed so that it is beneficial, not detrimental?