The Edwards Plateau region in Central Texas is an elevated expanse of land covering 35,000 square miles in area. It is bordered on the south and east by the Balcones Escarpment, also known as Balcones Canyonlands. When Spanish explorers first saw the terraced hills of the Edwards Plateau region, they named the land Balcones. The primary purpose of the refuge is to conserve the nesting habitat of the endangered Golden-cheeked Warbler and Black-capped Vireo. Limestone hills and spring fed canyons make up most of the Balcones Canyonlands National Wildlife Refuge, and the vegetation found in this area include various oaks, elm, and Ashe juniper trees. The Golden-cheeked Warbler and Black-capped Vireo depend on different successional stages of this vegetation.
European settlers came to the Edward?s Plateau region in the mid-1800?s and immediately created major landscape changes to the region, mainly through overgrazing of cattle and sheep. Along with historical habitat destruction, the current rate of urban development, in the Texas Hill Country, is removing and fragmenting wildlife habitat at an alarming rate. Acquiring the Refuge represents one of the last opportunities to obtain and manage a large block of the Texas Hill Country habitat. The Refuge, first established in 1992, is important to conserving the natural diversity of the Balcones Canyonlands ecosystem, including all the unique species and the habitat upon which they depend. Habitat management is primarily for the Black-capped Vireo and Golden-cheeked Warbler. Black-capped Vireo habitat is characterized by mid-successional shrub vegetation. Golden-cheeked Warbler habitat is characterized by large stands of mature trees (oaks, Ashe juniper, escarpment cherry, elms, etc.) found in and around steep canyons and hillsides, exclusively in Texas. Currently the Refuge manages 4,223 acres to conserve and protect the nesting habitat of the endangered Golden-cheeked Warbler and 1,482 acres for the Black-capped Vireo.
Lying below the Edwards Plateau is the karst habitat, an underground honeycomb of caves, sinkholes and springs. Endangered invertebrates inhabit these caves and are unique to this area of Texas. Even deeper below the surface lies the Edwards Aquifer, which stores billions of gallons of water that supply drinking water for the almost one million people in the San Antonio, Texas area. The aquifer is also the source of many Central Texas springs rivers, which eventually flow into the marshes, estuaries, and bays along the Texas coast. Protection of the springs is vital to the plants and animals that depend on the purity of the water.
Critical: Federal funding shortfall for acquisition (lost opportunities, see below)
Critical: Housing development (loss of tracts within Refuge, encroachment around Refuge)
Critical: Excessive disturbance of birds (proposed local airport expansion)
Major: Other (which category?): Over-population of white-tailed deer
Major: Succession (for vireo habitat, maturation beyond desired seral stage)
Major: Succession (invasion of grassland, oak shinneries with Ashe juniper)
Major: Excessive soil erosion (historical, from past land use practices)
Major: Introduction of non-indigenous fauna (imported red fire ant)
Major: Parasitism (Brown-headed Cowbird parasitism of songbird nests)
Local: Grazing/browsing (cows, goats; introduction of cowbirds, loss of vegetation structure)
Local: Deforestation (clearing of juniper-oak woodlands)
Local: Natural pests/diseases (oak wilt)
Local: Extraction industry (a few limestone quarries)
Potential: Fire (extreme fire danger in juniper-oak woodlands, esp. at urban/wildland interface)
Primary: Deciduous woods (Texas oak woodland on mesic slopes)
Primary: Mixed woods (juniper-oak woodlands, oak-elm-juniper woodlands)
Primary: Shrub/scrub (successional oak shinnery, second-growth juniper shrublands)
Secondary: Natural grassland (little bluestem prairie, oak-elm savannahs)
Secondary: Riparian (pecan-elm bottomland, cedar elm-hackberry and sycamore-elm riparian woodlands)
Secondary: Other grassland (restored/recovering pasture and cropland)