Edwards Plateau

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Edwards Plateau
Edwards Plateau.png
A photograph taken by NASA of the Edwards Plateau and Balcones Escarpment
Edwards Plateau Savannas map.svg
Ecology
Realm Nearctic
Biome Temperate grasslands, savannas, and shrublands
Bird species191 [1]
Mammal species64 [1]
Geography
CountryUnited States
State Texas
Conservation
Habitat loss5.35% [1]
Protected2.26% [1]

The Edwards Plateau is a geographic region forming the crossroads of Central, South and West Texas, United States. It is named in honor of Haden Edwards. [2] It is bounded by the Balcones Fault to the south and east; the Llano Uplift and the Llano Estacado to the north; and the Pecos River and Chihuahuan Desert to the west. [3] San Angelo, Austin, San Antonio and Del Rio roughly outline the area. The plateau, especially its southeast portion, is also known as the Texas Hill Country.

Contents

Natural history

Edwards Plateau terrain as seen from U.S. Route 277 between Del Rio and Sonora Terrain of the Edwards Plateau north of Del Rio, TX DDSCN0924.JPG
Edwards Plateau terrain as seen from U.S. Route 277 between Del Rio and Sonora

The bedrock consists primarily of limestone, with elevations ranging between 100 and 3000 ft. Caves are numerous.

The landscape of the plateau is mostly savanna scattered with trees. It mostly lacks deep soil suitable for farming, though the soil type is fertile mollisol, so some cotton, grain sorghum, and oats are grown. For the most part, though, the thin soil and rough terrain areas are primarily grazing regions, with cattle, sheep, and goats (Angora and meat types) predominant. [4] Several rivers cross the region, which generally flow to the south and east through the Texas Hill Country toward the Gulf of Mexico; springs occur (in wet years), but permanent surface water supplies are sparse throughout the area, except for man-made reservoirs. The area is well drained; rainwater flows into the Edwards Aquifer recharge zone at the south of the plateau to feed rivers to the south. Rainfall varies from 15 to 33 inches per year, typically, from northwest to southeast, and the area has a moderate temperature and a reasonably long growing season.

Flora

Trees of the savanna include Ashe junipers (locally called mountain cedar) and oak species, especially plateau live oak and Texas red oak, scattered over grasses such as little bluestem and sideoats grama, a vegetation type historically shaped by droughts and regular fires. Pecan trees are native in floodplains along springs and rivers, which are often lined with stands of baldcypress. [5] The Balcones Fault zone which runs along the southern and eastern edge of the plateau is an ecological demarcation for the ranges of a number of species.

Fauna

Caves of the Edwards Plateau are important habitats for wildlife and for many endemic species. The area is home to some of the largest colonies of bats in the world, including millions of Mexican free-tailed bats. The largest colony of these inhabits Bracken Cave near San Antonio, while the Congress Avenue Bridge in Austin is the summer home for over half a million (they winter in Mexico) and is the largest bat colony anywhere in an urban area. The Edwards Plateau is home to at least 14 endemic freshwater fishes, including two subterranean species of catfish [6] and 13 fish species considered to be spring-associated. [7] Mechanisms for spring association of fishes is not fully understood, but thought to mediated by water temperature. [8] The large numbers of reptiles and birds also include breeding populations of the Texan endemic golden-cheeked warbler (Setophagachrysoparia).

Much of the natural habitat of the plateau has been converted to residential development, especially around Austin and San Antonio in the eastern part of the plateau. Further alteration to the savanna has incurred though the encroachment of shrubs now that grassland fires are carefully controlled. Small areas of intact habitat remain in protected areas such as the Balcones Canyonlands National Wildlife Refuge and Lost Maples State Natural Area. Another important area for wildlife is Fort Cavazos military base. [9]

Human history

Enchanted Rock near Fredericksburg by Hermann Lungkwitz, 1864, oil on canvas Enchanted Rock near Fredericksburg.jpg
Enchanted Rock near Fredericksburg by Hermann Lungkwitz, 1864, oil on canvas

Earliest human settlement of this area was by Native Americans. [10] First it was used and wandered about by Jumano and Coahuiltecan groups, then the Apacheria extended into the Southern Plains by the forerunners of the Lipan and Mescalero Apaches. After the expulsion of the Apachean groups from the Plains by the Comanche, this area was dominated by the Penateka band of the Southern Comanche.

Counties in the Edwards Plateau

According to the Texas Parks and Wildlife Department, all or portions of these 41 counties comprise the Edwards Plateau geographic region: [11]

The Texas Water Development Board, a state government agency, includes additional counties all or partly in the Edwards Plateau area: [12]

A map showing the counties is provided by Texas Parks and Wildlife Department for the Edwards Plateau Ecoregion. [13] The ecoregion is somewhat larger than the geographic region, as the map from Texas Parks And Wildlife includes additional counties that are listed by the Texas Water Development Board, notably the isolated area of Edwards Plateau in Taylor, Runnels, and Nolan Counties that is separated from the main region.

See also

Related Research Articles

<span class="mw-page-title-main">Williamson County, Texas</span> County in Texas, United States

Williamson County is a county in the U.S. state of Texas. As of the 2020 census, its population was 609,017. Its county seat is Georgetown. The county is named for Robert McAlpin Williamson, a community leader and a veteran of the Battle of San Jacinto.

<span class="mw-page-title-main">Travis County, Texas</span> County in Texas, U.S.

Travis County is located in Central Texas. As of the 2020 census, the population was 1,290,188. It is the fifth-most populous county in Texas. Its county seat and most populous city is Austin, the capital of Texas. The county was established in 1840 and is named in honor of William Barret Travis, the commander of the Republic of Texas forces at the Battle of the Alamo. Travis County is part of the Austin–Round Rock–Georgetown Metropolitan Statistical Area. It is located along the Balcones Fault, the boundary between the Edwards Plateau to the west and the Blackland Prairie to the east.

<span class="mw-page-title-main">Texas Hill Country</span> Region of Texas

The Texas Hill Country is a geographic region of Central and South Texas, forming the southeast part of the Edwards Plateau. Given its location, climate, terrain, and vegetation, the Hill Country can be considered the border between the American Southeast and Southwest. The region represents the very remote rural countryside of Central Texas, but also is home to growing suburban neighborhoods and affluent retirement communities.

<span class="mw-page-title-main">Balcones Fault</span> Fault zone in Texas, United States

The Balcones Fault or Balcones Fault Zone is an area of largely normal faulting in the U.S. state of Texas that runs roughly from the southwest part of the state near Del Rio to the north-central region near Dallas along Interstate 35. The Balcones Fault zone is made up of many smaller features, including normal faults, grabens, and horsts. One of the obvious features is the Mount Bonnell Fault.

<span class="mw-page-title-main">Mount Bonnell</span> Hilltop and park in Austin, Texas

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<span class="mw-page-title-main">Barton Creek</span> River in the United States of America

Barton Creek is a tributary that feeds the Colorado River as it flows through the Texas Hill Country. The creek passes through some of the more scenic areas in Greater Austin, surrounded in many parts by a greenbelt of protected lands that serves as a habitat for many indigenous species of flora and fauna. The creek passes through Barton Creek Greenbelt and is fed by Barton Springs.

<span class="mw-page-title-main">Golden-cheeked warbler</span> Species of bird

The golden-cheeked warbler is an endangered species of bird that breeds in Central Texas, from Palo Pinto County southwestward along the eastern and southern edge of the Edwards Plateau to Kinney County. The golden-cheeked warbler is the only bird species with a breeding range endemic to Texas.

<span class="mw-page-title-main">Texas Blackland Prairies</span> Temperate grassland region of Texas, US

The Texas Blackland Prairies are a temperate grassland ecoregion located in Texas that runs roughly 300 miles (480 km) from the Red River in North Texas to San Antonio in the south. The prairie was named after its rich, dark soil. Less than 1% of the original Blackland prairie vegetation remains, scattered across Texas in parcels.

<span class="mw-page-title-main">Edwards Aquifer</span> Source of drinking water in Texas

The Edwards Aquifer is one of the most prolific artesian aquifers in the world. Located on the eastern edge of the Edwards Plateau in the U.S. state of Texas, it is the source of drinking water for two million people, and is the primary water supply for agriculture and industry in the aquifer's region. Additionally, the Edwards Aquifer feeds the Comal and San Marcos Springs, provides springflow for recreational and downstream uses in the Nueces, San Antonio, Guadalupe, and San Marcos river basins, and is home to several unique and endangered species.

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The term Cross Timbers, also known as Ecoregion 29, Central Oklahoma/Texas Plains, is used to describe a strip of land in the United States that runs from southeastern Kansas across Central Oklahoma to Central Texas. Made up of a mix of prairie, savanna, and woodland, it forms part of the boundary between the more heavily forested eastern country and the almost treeless Great Plains, and also marks the western habitat limit of many mammals and insects.

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<span class="mw-page-title-main">Pedernales Falls State Park</span> State park in Texas, United States

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Palaemon antrorum, also known as the Balcones cave shrimp and the Texas cave shrimp, is a species of palaemonid shrimp endemic to Texas. It is listed as an endangered species on the IUCN Red List, and as a Species of Concern by the United States Endangered Species Act.

<span class="mw-page-title-main">Tamaulipan mezquital</span> Xeric shrublands ecoregion in Mexico and the United States

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<span class="mw-page-title-main">Balcones Canyonlands National Wildlife Refuge</span> National Wildlife Refuge in Texas

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Comanche Springs was an aquifer of six artesian springs geographically located between the Edwards Plateau and the Trans-Pecos regions of West Texas. The military fortification Camp Stockton was built around the springs, eventually growing become the city of Fort Stockton.

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References

  1. 1 2 3 4 Hoekstra, J. M.; Molnar, J. L.; Jennings, M.; Revenga, C.; Spalding, M. D.; Boucher, T. M.; Robertson, J. C.; Heibel, T. J.; Ellison, K. (2010). Molnar, J. L. (ed.). The Atlas of Global Conservation: Changes, Challenges, and Opportunities to Make a Difference . University of California Press. ISBN   978-0-520-26256-0.
  2. ↑ McCrain, James. "Edwards County". TSHA.
  3. ↑ Demarest, D. "Edwards Plateau". Partners in Flight. Archived from the original on May 21, 2013. Retrieved September 2, 2014.
  4. ↑ Johnson, E. H. "Edwards Plateau". Handbook of Texas Online. Retrieved March 12, 2009.
  5. ↑ Hill, Robert T. (1891). "A brief description of the Cretaceous rocks of Texas and their economic uses". In E. T. Dumble (ed.). First Annual Report of the Geological Survey of Texas, 1889. Austin: State Printing Office. p. 134. Archived from the original on June 21, 2010. Retrieved March 21, 2010.
  6. ↑ Bowles, David E.; Arsuffi, Thomas L. (December 1, 1993). "Karst aquatic ecosystems of the Edwards Plateau region of central Texas, USA: A consideration of their importance, threats to their existence, and efforts for their conservation". Aquatic Conservation: Marine and Freshwater Ecosystems. 3 (4): 317–329. Bibcode:1993ACMFE...3..317B. doi:10.1002/aqc.3270030406. ISSN   1099-0755.
  7. ↑ Craig, Cody A.; Kollaus, Kristy A.; Behen, Kenneth P. K.; Bonner, Timothy H. (February 1, 2016). "Relationships among spring flow, habitats, and fishes within evolutionary refugia of the Edwards Plateau". Ecosphere. 7 (2): n/a. Bibcode:2016Ecosp...7E1205C. doi: 10.1002/ecs2.1205 . ISSN   2150-8925.
  8. ↑ Bonner, Timothy H.; Maikoetter, Jeremy D.; Craig, Cody A. (January 4, 2019). "Temperature-mediated feeding between spring-associated and riverine-associated congeners, with implications for community segregation". PeerJ. 6: e6144. doi: 10.7717/peerj.6144 . ISSN   2167-8359. PMC   6322479 . PMID   30631643.
  9. ↑ "Edwards Plateau". Terrestrial Ecoregions. World Wildlife Fund.
  10. ↑ Maria de Fátima Wade. 2003. The Native Americans of the Texas Edwards Plateau, 1582-1799, University of Texas Press, 293 pages ISBN   0-292-79156-9, ISBN   978-0-292-79156-5
  11. ↑ Texas Parks and Wildlife http://www.tpwd.state.tx.us/huntwild/wild/birding/pif/assist/pif_regions/region_7.phtml
  12. ↑ Mace, Robert. "Aquifers of the Edwards Plateau" (PDF). Texas Water Development Board. Retrieved October 11, 2020.
  13. ↑ "Ecoregions of Texas" (PDF). Texas Parks And Wildlife. Retrieved October 12, 2020.

30°18′N99°36′W / 30.3°N 99.6°W / 30.3; -99.6

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