The pattern of land use of historic prairie generally involved tall-grass prairie becoming corn and bean farms, mixed-grass prairie becoming wheat fields and other crops, and short-grass prairie becoming rangeland. Replacement of long-rooted prairie grasses with forage crops has left the landscape vulnerable to the effects of overgrazing. Rangelands are susceptible to soil erosion and drought among other threats.
According the U.S. Census of Agriculture figures from 2007, there are 2,204,792 farms in the United States, of which nearly 700,000 graze livestock. In addition, there are over 278 millions acres of federal lands which permit grazing.
Prairies evolved with the presence of fire and grazing by buffalo; however, cattle differ from buffalo in that cattle will pull up an entire plant while buffalo graze the top portions of plants and move on.
Cattle grazing can result in a slowing of root growth, lowered moisture-carrying capacity, and overall loss of plant vigor, making forage more susceptible to disease and replacement by invasive species.
The U.S. Bureau of Land Management estimates that 58 percent of its 150 million acres of rangeland is in fair or poor condition due in part to overgrazing.
Because livestock prefer riparian or water bank habitats, effects of overgrazing have spread to aquatic and wildlife habitats, causing stream sedimentation and a reduction in photosynthesis and primary production.
- Photo Credit Pat Walden/Stock.xchng, Leo Cumings/Stock.xchng
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