Overgrazing

Causes

Overgrazing is caused by inappropriate grazing practices, such as high animal-to-land density on a parcel of land for extended periods, that inhibit vegetation cover in combination with poor land management (e.g., lack of vegetation rotation, grazing during inappropriate vegetation life cycle and productivity, inappropriate species, grazing on lands that are poor for grazing or have previously been degraded by grazing). Land management is more critical because a few ungulates can overgraze an area if not managed properly. Similarly, if the land is properly managed, a large population of ungulates could live on a parcel of land without the damage of overgrazing occurring. Management of land is limited by access to suitable rangelands, competition with agricultural land, and available water resources, all of which cause grazing ungulates to utilize the marginal lands.

Overgrazing Effects

The effects of overgrazing on the natural vegetation are frequently irreversible, and the practice significantly contributes to loss of topsoil, increased surface runoff, desertification, and the loss of biodiversity. The main ecological effect of overgrazing is the loss of vegetation cover as a result of inappropriate grazing, especially in temperate and tropical highland savannas and drylands (i.e., semi-desert, grassland, and range-land) located primarily in the global south. These savannas and drylands are home to some of the most impoverished people in the world. The practice of overgrazing allows the population to raise food in the short term, but the fragility of the drylands’ ecosystems results in the limited vegetation being significantly degraded, which results in topsoil loss, and the areas then become prone [Page 704]to erosion, making it difficult for the people to utilize the local resources.

Overgrazing reduces or removes the amount of vegetation of a pastureland and is detrimental to the habitat and ecosystem. For example, the grazing ungulates do not eat all the vegetation; instead, they selectively graze the most edible species and leave weeds and the least edible species. The noneaten species become the dominant species for the ecosystem, resulting in the land being less suitable for future grazing. Aside from the proliferation of unwanted plants, the overall loss of vegetation causes reduced groundcover and the plants being distributed more sparsely.

Overgrazing is damaging to the soil because of the loss of vegetation and because the soil becomes compacted by the grazing ungulates. The loss or reduction of vegetation results in the soil being exposed to higher temperatures via direct sunlight, and many species die off. Many of the remaining and subsequent plant generations have shallow root systems, which in turn diminishes the soil's ability to hold down the soil, making it vulnerable to wind and water erosion. The compact soil makes it more difficult for future plant generations to grow. The loss of vegetation decreases the amount of organic material (e.g., humus) available for replenishing the soil with nutrients. Ultimately, the damage to the topsoil results in the pastureland becoming a barren wasteland. In addition, the loss of vegetation concentration, soil degradation, and shallow root systems result in the cultivation of seral communities and make the degraded grazing lands susceptible to fires.

...