Some argue that calculations of the number of livestock a region can support are a poor indicator of degradation on Africa's arid rangelands because the environment is so drought-prone. They conclude that drought destroys the vegetation with or without cattle. Others point out that measuring degradation in drier areas by the presence of annual, rather than perennial, plants is misleading because annuals are native there. Although the environmental status of drier rangeland may defy simple quantification, there is little debate that degradation is occurring in environments where rainfall is more plentiful and regular. In addition, these areas can support crops, so farmers have crowded pastoralists and their herds onto smaller areas, accelerating degradation.
Ranchers commonly overstock their land with cattle, leading to weed invasion and erosion.
In the savannas of northern and central Mexico, livestock are stocked at nearly four times the land's carrying capacity. And wealthy nations are not immune from the effects of overgrazing on rangeland. Spain and Portugal still bear the scars of pro-sheep land policies that began hundreds of years ago. Other studies indicate that half of US rangeland is severely degraded, with its carrying capacity reduced by at least 50 percent, and that the narrow streambank habitats crucial to arid-land ecology are in the worst condition in history. Damage to rangeland is only one measure of the destructiveness of current grazing patterns.