The layers of Santa Elena limestone visible on the canyon walls here in Big Bend National Park are evidence that where we are standing was once a shallow sea. Human effect did not cause this sea to shrink to its present Pacific shoreline. Earth’s evolution left this marvel, one of few public lands in the Lower 48 where the KT layer, the strata marking the Cretaceous and Tertiary periods of geologic time, is exposed and can be seen.
There is a vast area of the Park, though, that gives sobering evidence of the long-lasting change that humans can inflict upon an environment. Now it is called Tornillo Flat. Stretching on either side of the mostly dry Tornillo Creek, thousands of acres are nothing but rocky sand, parched by a relentless sun, and dotted by lonely mesquites and a forest of creosote bush, as far as the eye can see.
Had you been here in the 1870s when US military expeditions first surveyed the Big Bend, a much different sight would have greeted you. The Great Comanche Trail followed the path carved by Tornillo Creek. On either side of the creek, as far as the Comanches could see from horseback, as they drove their plundered cattle and horses back from their raids into Mexico, was grass tall enough to brush the bellies of their livestock. Their trail followed sources of water and food for their herds.
From forts along the Trans-Pecos, US Cavalry troopers, many Black Buffalo Soldiers, made southwest Texas safe for settlement by winning the Indian Wars. With Comanche raids marked only by memories and an October moon named for their lunar-lit travels, both Anglos and Mexicanos began to settle a land the early Spanish called ‘el despoblado,’ ‘the uninhabited place.’
By the early years of the Twentieth Century, some Mexican ranchers owned smaller holdings in the Big Bend, where the Rio Grande takes a sharp left, then right turn, on its way to the Gulf of Mexico. Anglo neighbors held title to larger ranches. While it was never easy living on these ranches and among the Mexicano-populated villages, with the Eastern demand for beef, mohair and mutton, the ranchers and their cowboys managed a living into a second generation.
By the late 1930s, word was out that the State of Texas was buying land for a new ‘Canyonlands’ State Park. With a recognition that they would not be long on their land, what with the possibility of a National Park, some ranchers began to push their land beyond its capacity. Over-grazing denuded grasslands. In places like Tornillo Flat, the very structure of the sod was uprooted.
What had been grasslands in the 1870s by 1944 had become desert. Now, a hundred years after ranches dotted the Big Bend, Tornillo Flat is still a wasteland. Although Park efforts to restore grass has been ongoing for a number of years, it is unlikely that it will ever be restored.
Here, where there was once a shallow sea complete with dinosaurs along its salty wetlands, the earth matured over millions of years to support a complex menagerie of insects, birds, reptiles and mammals. Then in the course of fifty or so years, humans destroyed an ecosystem.
Mr. Rubio from Florida, may not be able to tell you how old the earth is, since he is not a scientist, but I am here to bear witness that it is not so old and resistant that we cannot wreak havoc upon it. Only the willfully ignorant can doubt the effect of humans upon our planet.