Edwards Plateau Ecological Region
The Edwards Plateau Ecological Region of Texas extends in the southwestern regions of Northcentral Texas and includes portions of Concho, Tom Green, Irion, Sterling, Glasscock, Reagan, and Irion counties and an separate area to the north in Coke, Taylor, and Nolan counties. The Edwards Plateau is an uplifted and elevated region originally formed from marine deposits of sandstone, limestone, shales, and dolomites 100 million years ago during the Cretaceous Period when this region was covered by an ocean. The western portion remains a relatively flat elevated plateau whereas the eastern portion known as the Hill Country is deeply eroded.
When the Edward Plateau region was settled by European man in the mid-1800s, it was maintained as a grassland savannah largely by grazing habits of bison and antelope as well as by frequent natural and man-made fires. The land supported a rich diversity of forbs and grasses. Cedar was restricted to overgrazed areas along rivers and streams, and in areas of shallow soils and steep canyons where fires did not occur frequently. White-tailed deer were rarely found in the grasslands. With European settlement came fences, cows, sheep, goats and the control of fire. Livestock were continuously grazed in fenced pastures which disrupted the natural movement patterns of grazing animals. Plants were not allowed to rest and recover from grazing. By 1900, continuous overgrazing and control of fire had taken its toll. The land began to change from a grassland to a brushland. Many of the woody brush species were readily grazed by sheep, goats, cattle, and an increasing deer herd. These animals have selective eating habits and eat the more desirable plants first and leave the less desirable plants for last. By the 1940's, many of the good quality plant species were highly depleted and not readily found on most ranges. The Edwards Plateau is now dominated by many poor quality browse, forb, and grass plants. Ashe juniper and red berry juniper (commonly called cedar) are highly undesirable forage plants for domestic livestock and deer. In much of the Edwards Plateau, cedar has become the dominant plant species causing a once diverse and healthy landscape to become a "cedar break" in many areas with very little plant diversity on the landscape.
Pronghorn antelope are found on several large ranches in this portion of Northcentral Texas and white-tailed deer population often exceed range carrying capacity. Drought is a common occurrence in this region that periodically has long term affects on wildlife populations and habitat resources. Low reproduction rates and survival of white-tailed deer and pronghorn fawns often results in downward population trends. Live oak, shin oak, Texas oak, blueberry and redberry juniper, mesquite, lotebush, yucca, pricklypear, persimmon, hackberry, catclaw, pricklyash, bumelia, sumac species, and many other woody species are common in most plant communities and contribute to habitat for many wildlife species as food and cover.
See Hill Country Wildlife Management page for additional information about the Edwards Plateau