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Cattle Fill Ecological Niche Where Buffalo No Longer RoamBy Don Comis
May 6, 1999
If the Central Great Plains can't have the buffalo back, the Plains should at least have a cow every 16 acres. This moderate grazing level makes for the most diverse and productive ecosystem, according to new findings of U.S. Department of Agriculture studies begun 60 years ago at the end of the Dust Bowl era.
The Dust Bowl was named for the billions of tons of dry soil blown away during years of drought in the overcropped Plains. Arguably the century's worst farming, ecological, economic and social disaster, the Dust Bowl taught a costly lesson. Agriculture could thrive long term only when compatible with soil, water and other resources--and climate.
After the Dust Bowl disaster, much of the Plains was returned to soil-protecting plants and grazing. Scientists have been working on determining grazing rates that would even out growth of individual plant species while preventing any from dominating in different parts of the Plains.
In northern Colorado, that rate is one yearling heifer per 16 acres, and ranch profitability turns out to also be highest at this moderate level, according to researchers with the Agricultural Research Service, USDA's chief scientific agency. ARS rangeland scientist Richard Hart and colleagues in Cheyenne, Wyo., conducted the studies on USDA's Central Plains Experimental Range near Nunn, Colo., about 40 miles south of Cheyenne. Yearling heifers have been grazed there five or six months a year since 1939. The range, established on abandoned Dust Bowl farms and ranches, is one of the world's longest running rangeland-grazing experiments.
ARS scientists counted 46 plant species on moderately grazed land, 43 under heavy grazing and 36 under light grazing. Cattle weight gains dropped on heavily grazed land, since there were more mouths to feed and less forage to go around. Ungrazed land had 46 species but low biodiversity; pricklypear cactus dominated.
A story on the research appears in the May issue of Agricultural Research and on the web at: