Overgrazing

"OVERGRAZING"

Overgrazing occurs when plants are exposed to intensive grazing for extended periods of time, or without sufficient recovery periods. It can be caused by either livestock in poorly managed agricultural applications, game reserves, or nature reserves.

 

Causes Of Overgrazing

Overgrazing occurs when too much green material is repeatedly removed from a plant and it does not have sufficient leaf mass to regrow. Residual plant matter is needed to hold the soil and prevent erosion by water or wind. Overgrazed rangeland is often characterized by an increase in weeds or unpalatable plants, increased soil erosion, and a decrease in the biomass of important forage plants. Rangelands typically receive less precipitation than more productive farmland, and have few or low growing plants which shouldn't be confused with an overgrazed site. Overgrazing should not be confused with overstocking. Overstocking is when a site is heavily stocked with more animals than the site could support for a grazing season, such as is often the case with targeted grazing. However, poor management coupled with overstocking can severely degrade a site.

Effects of Overgrazing 

(i) Land Degradation:

Overgrazing removes the vegetal cover over the soil and the exposed soil gets compacted due to which the operative soil depth declines. So the roots cannot go much deep into the soil and adequate soil moisture is not available.

Organic recycling also declines in the ecosystem because not enough detritus or litter remains on the soil to be decomposed. The humus, content of the soil decreases and overgrazing leads to organically poor, dry, compacted soil.

Due to trampling by cattle the soil loses infiltration capacity, which reduces percolation of water into the soil and as a result of this more water gets lost from the ecosystem along with surface run off. Thus overgrazing leads to multiple actions resulting in loss of soil structure, hydraulic conductivity and soil fertility.

(ii) Soil Erosion:

Due to overgrazing by cattle, the cover of vegetation almost gets removed from the land. The soil becomes exposed and gets eroded by the action of strong wind, rainfall etc. the grass roots are very good binders of soil. When the grasses are removed, the soil becomes loose and susceptible to the action of wind and water.

(iii) Loss of Useful Species:

Overgrazing adversely affects the composition of plant population and their regeneration capacity. The original grassland consists of good quality grasses and herbs with high nutritive value.

When the livestock graze upon them heavily, even the root stocks which carry the reserve food or regeneration get destroyed. Now some other species appear in their place. These secondary species are hardier and are less nutritive in nature. Some livestock keep on overgrazing these species also.

Solutions

Overgrazing is a phenomenon that is exactly what the term suggests, when land used for pasture and grazing for livestock is overly grazed, resulting in poor vegetation growth.  This occurs because the grass and native vegetation does not have enough recovery time to replenish itself.  This can have catastrophic effects on the ecosystem the land is contained in, resulting in erosion of the land because of a breakdown in the root systems.  Some solutions to the problem of overgrazing would be livestock rotation and the planting of warm-weather grasses along with cool weather grasses.  Livestock should be rotated to other pasturelands to give the vegetation enough time to recover and grow back.  Also, the planting of cool weather grasses will take off the pressure from warm weather grasses and give a longer production period for vegetation to grow. 

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