Bison, Cattle, and the Shortgrass Prairie of West Texas and New Mexico
Cattle herds managed under “holistic planned grazing” can replace the animal impact of missing bison herds. As explained below, grazing by large animals is necessary for grassland health.
NOTE: article originally appeared in the Hudspeth County Herald on November 6th, 2015
Though the American bison, or buffalo, is now a national icon, in the 1870s it was U.S. government policy to eradicate the animal. For railroads and cattle ranchers, bison were unwelcome. The policy was also designed to crush the Plains Indians, and the effort ended ways of life that had persisted for more than 10,000 years.
But bison were not only at the center of Native cultures. The creatures were also a cornerstone of the grassland ecosystems of the Great Plains. Their decimation forever altered those ecosystems. On the Llano Estacado, which was once prime buffalo habitat, the impact was acute.
The rich soils of the Great Plains have been one of the country’s most valuable natural resources. But before the plains were a breadbasket, they were grasslands. In the early 19th century, open prairies stretched from the Mississippi River to the Rocky Mountains. The plateau of the Llano Estacado, in Eastern New Mexico and West Texas, was part of this grassland terrain.
The relatively wet climate of eastern plains – from Oklahoma to Iowa – supported tallgrass prairies. Grasses there grew to heights of 10 feet. In arid West Texas, it was a shortgrass prairie, dominated by blue grama and buffalograss.
“Grazing animals and grasses co-evolved,” Michael Nickell, museum scientist at the Sibley Nature Center in Midland, said. “You really can’t have one without the other.”
The prairie grasses and bison existed in a state of mutual dependence. Bison had evolved teeth and a circular chewing motion capable of grinding down tough grasses. And a protozoa in the bison’s gut allows the animal to digest cellulose and absorb nutrients from grasses.
The grasses, in turn, developed a mechanism for new growth that capitalized on grazing activity.
In most plants, new growth takes place at the tip of the limb, in a cluster of undifferentiated cells called an “apical meristem.” But prairie grasses are different, Nickell said.
“Grasses have what’s called a basal meristem,” he said, “so all their cell reproduction is at the base of the plant, and so the plants are being nibbled down almost to the ground, but they still grow back – they grow new shoots. If there’s any shoots of shrubs and things like that that are beginning to sprout up, they’re going to get nipped by the grazing animals, and they’ve got apical growing points, and you’ve just stunted the growth of that plant right there, like a little mesquite or whatever.”
The bison-eradication program of the 1870s was extremely effective. The herds were already diminished by a drought and a demand for buffalo hides and tongues. By 1875, the southern bison herd, centered on the Llano Estacado, had been reduced from 2 million to a few hundred animals.
Over 100,000 buffalo skulls were estimated to be in this pile
Buffalo were what ecologists call a “keystone species.” Their presence shaped the ecosystem, influencing what other plants and animals could live here. Grazing pressure from bison had confined mesquite and other shrubs to draws and arroyos. But with the bison gone, those shrubs established themselves on the prairie. The grasslands began their transformation into the mesquite brushlands that predominate today.
The eradication of bison herds was only one of several disruptions to the grassland ecosystem. Prairie dogs, once ubiquitous on the prairies, were targeted as hazards to livestock. The prairie dogs had also played the role of a “keystone species,” Nickell said.
“They did pretty much the same thing that the bison did,” Nickell said, “except they didn’t migrate like the bison did, but instead they spread out all over creation. And so any shrub that would come in and get sprouted, they would nip it off. They don’t want any trees or shrubs sprouting up to block their view. Most of their predators are going to be coming from the air.”
The suppression of wildfire impacted the grasslands, as did farming and ranching. By the early 20th century, the ancient shortgrass prairie had essentially vanished. Where grasses have returned to the Llano Estacado, most are not native species
“As far as the world is concerned, probably the prairies are the most endangered,” Nickell said. “In North America, the grassland prairie is probably the most endangered of all ecosystems. It’s certainly the most altered.”
Military planners and buffalo hunters knew the bison was a mighty animal. But they didn’t know the outsized role it played in the grasslands of West Texas.
Nature Notes is underwritten by the Dixon Water Foundation and is produced by Marfa Public Radio in cooperation with the Sibley Nature Center in Midland, Texas.This installment was written by Andrew Stuart. Nature Notes can be heard on Marfa Public Radio, at 93.5 FM, on Tuesdays and Thursdays at 7:35 a.m. and 3:45 p.m., Mountain Time, and again Thursday nights after the newscast aired at 6 p.m.
Properly grazed cattle herds help make plants healthy just like bison herds used to do. Here is an example: This winter we are running 500 heifers at Circle Ranch. Fresh feed is placed daily where we need animal impact. Pastures are changed every few days.
Here is a different example of how to use cattle to restore soil fertility and plants.
Plants need animals as much as animals need plants. In both these grazing examples, grazing is planned to mimic nature, and increased soil fertility is the end game .