This article has been reviewed by the following Topic Editor: Mark McGinley
Introduction
Last Maples SNA, near Vanderpool, Texas, United States (Photograph by Roy Heideman)
The Edwards Plateau Savannas form an important part of the Texas Hill country, a moderately-sized ecoregion separated from adjacent units by a distinct soil type (mollisols) and a vegetation type distinguished by juniper-oak savanna and mesquite Acacia savanna underlain by mid to short grasslands. In other aspects, the Edwards Plateau Savannas is an ecoregion that is intermediate among the dry grassland and savanna ecoregions in terms of rainfall, temperature, and length of growing season. It is estimated that up to 90 percent of this ecoregion has been converted to pasture, urban areas, and agricultural crops. Previously, major disturbance regimes were dominated by fire, drought, and perhaps grazing by bison (Bison bison).
The limestone bedrock of the Edwards Plateau helps to contribute to the distinctiveness of the biota. An array of species are specialists on limestone habitats, including caves. Some of the largest assemblages of cave-dwelling bats anywhere in the world, indeed the largest aggregations of mammals anywhere in the world, roost in several of the large caves of this ecoregion. Millions of Mexican free-tailed bats (Tadarida brasiliensis) use these caves as maternity roosts, creating a globally outstanding phenomena. The high number of endemic invertebrate cave species also qualify this ecoregion as a global hotspot for cave-dwelling species. The aquatic vertebrates endemic to the Plateau include the widemouth blindcat (Satan eurystomus), San Marcos salamander (Eurycea nana), Comal blind salamander (Eurycea tridentifera), Texas blind salamander (Typhlomolge rathbuni), Blanco blind salamander (Typhlomolge robusta), and the Texas salamander (Eurycea neotenes).
This ecoregion also ranks among the top ten ecoregions for reptiles and birds. The Edwards Plateau Savannas contains most of the breeding habitat for an endemic migratory warbler, the golden-cheeked warbler (Dendroica chrysoparia), which nests only in mature oak-juniper savannas, or cedar brakes. Some important breeding habitat for the black-capped vireo (Vireo atricapillus), a species endangered by habitat loss, occurs in this ecoregion. A disjunct population of maples (Acer spp.) occur in mesic pockets, an unusual example of a relict population in a presently dry region.
Conservation Status
Habitat Loss and Degradation
Only about two percent of the remaining habitat in this important ecoregion is considered intact. Important ecological processes such as fire have been suppressed, leading to changes in vegetation structure and composition. Extensive soil loss has contributed to changes in the disturbance regimes of riparian communities. Overgrazing has fragmented and eliminated native grasslands and contributed to the expansion of woody species.
The southern and western portions of the Edwards Plateau are heavily altered by major encroachment of shrubs as a result of fire suppression. The eastern section of the plateau is in better condition and contains much second growth.
Remaining Blocks of Intact Habitat
The Edwards plateau contains only a few relatively small areas of intact habitat. These occur around Austin, where about 30 percent of a 182 square kilometers (km2) tract has been acquired and put under conservation management. About 50 percent of a 122 km2 tract in the Balcones Canyonlands has been acquired. Other intact blocks remain in Real County along the Frio River and in small patches outside San Antonio in northwest Bexar County.
West of Bandera, Texas, United States (Photograph by Robert Parvin)
When acquired, the new wildlife refuge near Austin and the Balcones Canyonlands will improve protection of biodiversity. Until then, many of the area's threatened species and habitats face considerable risk.
Types and Severity of Threats
Urban and suburban sprawl around Austin and San Antonio pose a high threat to remaining habitats. Invasion of exotic species and overgrazing will also increase habitat degradation unless mitigated by conservation measures. Cedar choppers in the hill country have removed much of the old growth juniper-oak woodland. Change in riparian disturbance regimes affects the dynamics of this system and threatens species dependent upon this habitat.
Suite of Priority Activities to Enhance Biodiversity Conservation
Priority sites for conservation include:
Areas along the Balcones Escarpment
Areas in western Travis County and northwest Bexar County that preserve the best remaining contiguous habitat of the golden-cheeked warbler
Karst areas that contain the highest concentration of Mexican free-tailed bat maternity colonies in the world
Fort Hood, which contains the largest population of golden-cheeked warblers and black-capped vireos under a single management unit, as well as significant karst features
Areas of high salamander diversity and endemism. Some individual springs, streams, and artesian wells are the only known localities for some species.
National, State, and local Chapter of the Audubon Society
Native Plant Society of Texas
The Nature Conservancy
The Nature Conservancy - Southeast Regional Office
The Nature Conservancy of Texas
Save our Springs Association
Sierra Club, Lone Star Chapter
Relationship to Other Classification Schemes
The boundary of the Edwards Plateau Savannas is taken from Omernik. It generally corresponds to Küchler’s juniper-oak savanna and Bailey section 315D (Edwards Plateau).
Additional Information on this Ecoregion
For a shorter summary of this entry, see the WWF WildWorld profile of this ecoregion.
To see the species that live in this ecoregion, including images and threat levels, see the WWF Wildfinder description of this ecoregion.
Disclaimer:
This article is taken wholly from, or contains information that was originally published by, the World Wildlife Fund. Topic editors and authors for the Encyclopedia of Earth may have edited its content or added new information. The use of information from the World Wildlife Fund should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content.
Are you absolutely sure you want to delete this article? This process cannot be undone and is permanent.
World Wildlife Fund (Lead Author);Mark McGinley (Topic Editor) "Edwards Plateau savanna". In: Encyclopedia of Earth. Eds. Cutler J. Cleveland (Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment). [First published in the Encyclopedia of Earth August 25, 2008; Last revised Date August 25, 2008; Retrieved May 26, 2012 <http://www.eoearth.org/article/Edwards_Plateau_savanna>
The Author
Known worldwide by its panda logo, World Wildlife Fund (WWF) leads international efforts to protect endangered species and their habitats. Now in its fifth decade, WWF works in more than 100 countries around the globe to conserve the diversity of life on Earth. With nearly 1.2 million members in the U.S. and another 4 million worldwide, WWF is the world's largest privately financed conservation organization. WWF directs its conservation efforts toward three global goals: 1) saving endangered ... (Full Bio)
Introduction
Last Maples SNA, near Vanderpool, Texas, United States (Photograph by Roy Heideman)
The Edwards Plateau Savannas form an important part of the Texas Hill country, a moderately-sized ecoregion separated from adjacent units by a distinct soil type (mollisols) and a vegetation type distinguished by juniper-oak savanna and mesquite Acacia savanna underlain by mid to short grasslands. In other aspects, the Edwards Plateau Savannas is an ecoregion that is intermediate among the dry grassland and savanna ecoregions in terms of rainfall, temperature, and length of growing season. It is estimated that up to 90 percent of this ecoregion has been converted to pasture, urban areas, and agricultural crops. Previously, major disturbance regimes were dominated by fire, drought, and perhaps grazing by bison (Bison bison).
The limestone bedrock of the Edwards Plateau helps to contribute to the distinctiveness of the biota. An array of species are specialists on limestone habitats, including caves. Some of the largest assemblages of cave-dwelling bats anywhere in the world, indeed the largest aggregations of mammals anywhere in the world, roost in several of the large caves of this ecoregion. Millions of Mexican free-tailed bats (Tadarida brasiliensis) use these caves as maternity roosts, creating a globally outstanding phenomena. The high number of endemic invertebrate cave species also qualify this ecoregion as a global hotspot for cave-dwelling species. The aquatic vertebrates endemic to the Plateau include the widemouth blindcat (Satan eurystomus), San Marcos salamander (Eurycea nana), Comal blind salamander (Eurycea tridentifera), Texas blind salamander (Typhlomolge rathbuni), Blanco blind salamander (Typhlomolge robusta), and the Texas salamander (Eurycea neotenes).
This ecoregion also ranks among the top ten ecoregions for reptiles and birds. The Edwards Plateau Savannas contains most of the breeding habitat for an endemic migratory warbler, the golden-cheeked warbler (Dendroica chrysoparia), which nests only in mature oak-juniper savannas, or cedar brakes. Some important breeding habitat for the black-capped vireo (Vireo atricapillus), a species endangered by habitat loss, occurs in this ecoregion. A disjunct population of maples (Acer spp.) occur in mesic pockets, an unusual example of a relict population in a presently dry region.
Conservation Status
Habitat Loss and Degradation
Only about two percent of the remaining habitat in this important ecoregion is considered intact. Important ecological processes such as fire have been suppressed, leading to changes in vegetation structure and composition. Extensive soil loss has contributed to changes in the disturbance regimes of riparian communities. Overgrazing has fragmented and eliminated native grasslands and contributed to the expansion of woody species.
The southern and western portions of the Edwards Plateau are heavily altered by major encroachment of shrubs as a result of fire suppression. The eastern section of the plateau is in better condition and contains much second growth.
Remaining Blocks of Intact Habitat
The Edwards plateau contains only a few relatively small areas of intact habitat. These occur around Austin, where about 30 percent of a 182 square kilometers (km2) tract has been acquired and put under conservation management. About 50 percent of a 122 km2 tract in the Balcones Canyonlands has been acquired. Other intact blocks remain in Real County along the Frio River and in small patches outside San Antonio in northwest Bexar County.
West of Bandera, Texas, United States (Photograph by Robert Parvin)
When acquired, the new wildlife refuge near Austin and the Balcones Canyonlands will improve protection of biodiversity. Until then, many of the area's threatened species and habitats face considerable risk.
Types and Severity of Threats
Urban and suburban sprawl around Austin and San Antonio pose a high threat to remaining habitats. Invasion of exotic species and overgrazing will also increase habitat degradation unless mitigated by conservation measures. Cedar choppers in the hill country have removed much of the old growth juniper-oak woodland. Change in riparian disturbance regimes affects the dynamics of this system and threatens species dependent upon this habitat.
Suite of Priority Activities to Enhance Biodiversity Conservation
Priority sites for conservation include:
Areas along the Balcones Escarpment
Areas in western Travis County and northwest Bexar County that preserve the best remaining contiguous habitat of the golden-cheeked warbler
Karst areas that contain the highest concentration of Mexican free-tailed bat maternity colonies in the world
Fort Hood, which contains the largest population of golden-cheeked warblers and black-capped vireos under a single management unit, as well as significant karst features
Areas of high salamander diversity and endemism. Some individual springs, streams, and artesian wells are the only known localities for some species.
National, State, and local Chapter of the Audubon Society
Native Plant Society of Texas
The Nature Conservancy
The Nature Conservancy - Southeast Regional Office
The Nature Conservancy of Texas
Save our Springs Association
Sierra Club, Lone Star Chapter
Relationship to Other Classification Schemes
The boundary of the Edwards Plateau Savannas is taken from Omernik. It generally corresponds to Küchler’s juniper-oak savanna and Bailey section 315D (Edwards Plateau).
Additional Information on this Ecoregion
For a shorter summary of this entry, see the WWF WildWorld profile of this ecoregion.
To see the species that live in this ecoregion, including images and threat levels, see the WWF Wildfinder description of this ecoregion.
Disclaimer:
This article is taken wholly from, or contains information that was originally published by, the World Wildlife Fund. Topic editors and authors for the Encyclopedia of Earth may have edited its content or added new information. The use of information from the World Wildlife Fund should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content.
Are you absolutely sure you want to delete this article? This process cannot be undone and is permanent.
Last Maples SNA, near Vanderpool, Texas, United States (Photograph by Roy Heideman)
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Mexican free-tailed bat (''Tadarida brasiliensis'') (Photograph by Bat Conservation International)
West of Bandera, Texas, United States (Photograph by Robert Parvin)
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