The Last Desert Grasslands

Disappearing grasslands

Westside of Alamo Mountain
Westside of Alamo Mountain

Otero Mesa has a long history of use and settlement by humans. However, for most of that history, modification of the landscape was localized and limited to areas adjacent to permanent water. We can get an idea of what the area looked like from U.S. survey reports following the war with Mexico in 1846-48. The original surveys described large expanses of “excellent” or “good” grassland in the valleys and plateaus between mountain ranges. Mesquite shrubs occurred so rarely that the surveyors took special note of their presence. In most places, soaptree yuccas were the only tall plants.

The pattern of land use changed dramatically after the American Civil war as a result of new technologies. The most important advance was the ability to drill deep wells and pump water by windmills. This allowed the livestock industry to expand into the waterless basins and mesas of the region. In addition, the expansion of railroads allowed cattle to be shipped to distant markets, spurring further growth in the industry.

By the early years of the twentieth century, overgrazing in combination with periodic droughts had damaged rangelands throughout the region and set in motion an irreversible process by which grasslands were converted shrublands. By the 1960s, virtually none of the original Chihuahuan Desert grasslands in the U.S. remained shrub free.

A number of factors were responsible for this dramatic transformation. The loss of vegetative cover reduced the ability of soils to absorb and store moisture. Rain falling on denuded watersheds led to increased runoff, erosion, and the lowering of water tables. Many springs and streams dried up. Today, most of the drainages in the region are ephemeral, with deeply incised channels that carry water only for very short periods following intense storms.

Indian Paintbrush on Flat Top Mountain.

Indian Paintbrush on Flat Top Mountain.

In many of the flat areas of the intermountain basins, the barren soil was exposed to wind erosion. Small silt particles were transported out of the region as aerosol dust while the sand particles were blown over the landscape. Where blowing sand encountered mesquite plants it was deposited to form coppice dunes. These dunes now occupy extensive areas of former black-grama grasslands. An example is the area surrounding the El Paso airport on land that is now part of Fort Bliss. High levels of grazing by domestic livestock reduced the height and abundance of grasses and herbaceous plants, and led to changes in the balance of rodent, rabbit and insect populations. The increase in bare soil and shrubs favored rabbits and certain rodents, putting more grazing pressure and stress on grasses, and further reducing their ability to compete with woody plants.

Although considerable research effort has focused on how to control “invasive” woody plants (especially mesquite and creosotebush) and on how to restore grasslands, rangelands continue to be plagued by an increasing abundance of shrubs and loss of grasses as the process of “desertification” continues.

The deterioration of the Chihuahuan Desert grasslands prompted ranchers to petition the U.S. government for help, leading to the establishment of research centers such as the U.S. Department of Agriculture’s Jornada Experimental Range (JER) north of Las Cruces, New Mexico. The focus of research at these centers was on grazing management and restoring the productivity of rangelands.

Records of vegetation changes at the 193,395 acre JER provide a clear picture of what has happened to the desert grasslands in southern New Mexico, southern Arizona and west Texas. In 1858, 60 percent of the JER was covered by grasslands with no or few shrubs, while mesquite shrubland accounted for 20 percent. A century later in 1960, essentially no grasslands remained while mesquite shrubland had increased to 60 percent of the land area. Similar scenarios have been described for other areas of southern New Mexico.

By the 1960s few areas remained of undegraded Chihuahuan Desert grassland in the United States. Surviving patches were usually small—less than 100 acres–and isolated, like grass atolls in a sea of mesquite savanna, mesquite coppice dunes, and other desert scrub formations. Otero Mesa is the rare exception.

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Coalition for Otero Mesa
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Contact us for more information about the Coalition for Otero Mesa, oil & gas development, or the ongoing effort to protect the last wild lands and open spaces in New Mexico.