"Mainstream" Science Finally
Learns Importance Of Grazing

(Editor’s note: Better late than never, "mainstream" scientists have finally discovered what ranchers and range management experts have been trying to pound into their heads for decades: that the world’s rangelands evolved under grazing, and thus need grazing animals to flourish. Who knows? In another 20 or 30 years, even environmental activists might wake up to the obvious. The Ted Turnerish romance with "bison" hinted at in the following article may grate on some readers, but it’s a start.)

WASHINGTON —(AP)— Where the buffalo go, more grasses will grow, researchers have discovered by measuring the effects of grazing in native tall-grass prairies.

Bison and other grazing animals are keys to keeping a healthy variety of grasses growing in the native prairie lands of North America, said Scott Collins, a National Science Foundation ecologist. Mowing the prairie also works, the scientist said.

Collins and his colleagues report on their findings in a study being published Friday in the journal Science.

In long-term field experiments, the researchers assessed the effects of fire, added nitrogen fertilizer, grazing and mowing on the variety of grasses that grow in a natural prairie.

Collins said they found the native prairies are being affected by the nitrogen put into the air by exhausts from cars. This fertilizing chemical tends to benefit some plants more than others, he said, and can diminish the species diversity.

In a natural prairie, he said, "nitrogen is a limited resource. When you take away the limitation and flush the system with nitrogen, a lot of plants that are good at sucking up nitrogen can dominate."

When people managing a prairie also burn the land periodically, to prevent trees from growing, and add fertilizer, it causes tall grasses to quickly create a canopy that blocks sunlight, said Collins. Short grasses and other plants cannot survive in the shade of this canopy, and diversity suffers.

However, if the canopy of tall grass is removed, by grazing or by mowing, he said, the prairie returns to a more natural state, with a much greater variety of grasses thriving.

Collins and his colleagues conducted the study in the Konza Prairie Long-term Ecological Research site in northeastern Kansas.

Tall grass prairies once stretched across parts of Illinois, Iowa, Kansas, South Dakota, Oklahoma and Texas. About 10 percent of such native prairie remains, in bits and pieces such as small plots along railroads, in cemeteries, near airports or in hay meadows.