Grasses spread through seed germination, and in some cases by underground and aboveground stems. As a general rule, root depth equals the height of the grass, but half of the root system dies back each year. This is natural and even desirable since the dead roots create new soil and you still have a sound root system if the grass isn’t topped too much. But heavy overgrazing causes grass roots to die back even more and creates an abnormally shallow root system. This is doubly dangerous in desert country where heat and the need to search out water pose crucial problems for all plants. Nor is this all, because other good things come—and other good things go—with a healthy ground cover. As each year’s grasses die back they fertilize the soil and insulate seedlings and roots from the sun’s killing heat, but when this cover is reduced, good grasses disappear and poorer grasses take over. Surface conditions are finally so changed that neither grasses nor grassland forbs and shrubs can grow. Seedlings may burst into brief life with a rain but when the sun bears down again day after day the unprotected plants perish. With nothing to hold it the soft topsoil blows and washes away. Desert downpours soon gully the ground, changing drainage patterns and lowering the water table beyond the reach of short grass roots. Longer rooted desert shrubs move in, first the shortlived tarbush, and finally creosotebush. The result is seen on Tornillo Flat today: typical Chihuahuan shrub desert with sparsely scattered creosotebush and cactuses.
What happened at Tornillo Flat also happened to other park grasslands. Chino grama, ignored by cattle and goats, but relished by sheep and horses, is and was the dominant grass of the Big Bend foothills. By 1944, overuse had so stripped the grasslands near Government Spring that you could hardly find a bunch of chino on the bare beige hills. Even in the mountains proper the grasses had all but disappeared, and biologists conducting an ecological survey found that the South Rim looked and smelled like a goat paddock.
Once the park was established and domestic animals were removed, native grasses got the chance to reestablish themselves. At first nature itself blocked recovery. For seven long years drought ruled all life in Texas. When the rains finally did come, grasses improved at different rates in different places. They had the most difficult time at lower elevations where heat and aridity are greatest. Several attempts to seed Tornillo Flat have been made, but it may take decades for these once bountiful bottomlands to green again. Grasses in the grassland belt surrounding the Chisos have made a remarkable comeback, however. In ten short years ground cover increased 30 percent. Grasses at the higher elevations are now probably as rich as ever.
The Fur Trade
Furs were an active commodity in the Big Bend until about 1940. Beaver once abounded along the river and its tributaries. Both fur bearers and predators were taken. The bighorn sheep was largely extirpated, selling for a time as “Mexican goat.” Wolves were extirpated before the park could provide refuge. Not all species were trapped. The javelina was hunted during World War I, for use in gloves, coats, and suitcases. The bristles went into brushes. Elmo Johnson (photo) bought furs from trappers at his trading post. Good profits required a good eye for raw furs, which Johnson possessed. Furs not trapped during the animal’s winter prime were nearly worthless, and values depended on their condition generally. No fur market existed in Mexico, so furs trapped there were sold at Texas trading posts, destined for the fur houses in St. Louis, Missouri. Only a portion of Johnson’s fur stocks shows in this 1929 photograph. Furs were a good business for him, because trappers took their value in goods, his first profit in the transaction. He then sold the furs for his second profit. Later, salaried government trappers worked this area to control predators. Today, all wildlife in the park is protected.
Gray fox
Mule Deer
