Playa lakes are integral wetlands of the Southern Great Plains. Playas, meaning "beach" in Spanish, are found in semiarid environments throughout the world but are most numerous in the Playa Lakes Region of southwestern Kansas, southeastern Colorado, the Oklahoma Panhandle, eastern New Mexico, and northwestern Texas. There are approximately 21,000 playa lakes on the Llano Estacado of Texas and New Mexico alone.
Playas are the most apparent topographical aspect of the essentially flat southern High Plains. They are small depressional wetlands, underlain by a clay soil, with a closed watershed. Perhaps the most ephemeral wetlands in North America, playas are dependent on localized, unpredictable, late spring and summer thunderstorms to collect and hold water. Playas can therefore be dry or flooded at any given time, and the plants and animals associated with them have to be able to adapt to such changeable conditions. Playas collect nearly 90 percent of the precipitation runoff on the southern High Plains and are the primary source of flood control. Most overlie the southern portion of the Ogallala Aquifer, and they provide approximately 80 percent of its annual water recharge. This is a critical function of playas, because the southern High Plains are heavily cultivated and grazed, and both endeavors are dependent on the Ogallala Aquifer.
Because of the dominance of agriculture, playas are the primary remaining wildlife habitat in the region. Most wildlife species in the area depend on playa habitats for existence. Thirty-seven mammalian species and almost 200 bird species have been reported in playas. Playas constitute vital nesting, migration, and wintering habitats for wetland birds, including shore and wading species. It has been estimated that nearly two million ducks, 600,000 geese, and 500,000 sandhill cranes winter in playas during wet years. Playas are also the principal breeding sites for amphibians in the region.
A total of 346 plant species are associated with playas. These include not only traditional wetland species but also many prairie plants no longer found in the surrounding uplands. Playas therefore serve as a seed repository for the flora of the region.
Threats to playas include physical alteration, direct application of agricultural chemicals, overgrazing, and sedimentation. Of these, sedimentation is the most serious. Approximately 90 percent of playas surrounded by cropland have lost their original volume due to sedimentation. At the current rate, all playas could fill with sediment within ninety-five years. Fortunately, measures are being taken to prevent or slow future sedimentation effects, restore degraded playas, and conserve these precious wetlands. These include taking land out of production through the Conservation Reserve Program, erosion control through contour farming, and creating buffers of native vegetation around the playas.
See also PHYSICAL ENVIRONMENT: Bird Migrations.
David A. Haukos Texas Tech University
Haukos, David A., and Loren M. Smith. Common Flora of the Playa Lakes. Lubbock: Texas Tech University Press, 1997.
Luo, Hong-Ren, Loren M. Smith, B. L. Allen, and David A. Haukos. "Effects of Sedimentation on Playa Wetland Volume." Ecological Applications 7 (1997): 247-52.