South Texas Plains ecoregion
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| South Texas Plains ecoregion | |
|---|---|
| Name | South Texas Plains |
| Area km2 | 185000 |
| Biogeographic realm | Nearctic |
| Biome | Temperate grasslands, savannas, and shrublands |
| Bordering | Tamaulipan mezquital, Gulf Coastal Plains, Chihuahuan Desert |
| Countries | United States |
| States | Texas |
South Texas Plains ecoregion The South Texas Plains ecoregion occupies the southernmost portion of Texas and forms a transition between the Gulf of Mexico coastline, the Chihuahuan Desert to the west, and the interior Tamaulipan mezquital and Eastern Temperate Forests to the east. Its landscape of thornscrub, grassland, and riparian corridors has been shaped by centuries of indigenous presence, Spanish colonial land grants, Republic of Texas era ranching, and modern U.S. Fish and Wildlife Service and Texas Parks and Wildlife Department conservation efforts aimed at species like the Northern Aplomado Falcon and Whooping Crane.
Geography and Boundaries
The ecoregion spans coastal plains, barrier islands, and inland brush country across counties including Cameron County, Texas, Hidalgo County, Texas, Willacy County, Texas, Starr County, Texas, Jim Hogg County, Texas, and Webb County, Texas. Major geographic features include the Rio Grande, Laguna Madre, and the Gulf Intracoastal Waterway, with nearby urban centers such as Brownsville, Texas, McAllen, Texas, Corpus Christi, Texas, and Laredo, Texas. It borders ecoregions mapped by the World Wildlife Fund and the Environmental Protection Agency (EPA), and contains protected areas like Bentsen-Rio Grande Valley State Park, Laguna Atascosa National Wildlife Refuge, and Santa Ana National Wildlife Refuge.
Climate
The climate is subtropical to semi-arid, influenced by the Gulf of Mexico and seasonal shifts tied to the North Atlantic Oscillation and El Niño–Southern Oscillation. Summers are hot and humid in coastal zones near Corpus Christi Bay and drier inland near Del Rio, Texas; winters can bring cold fronts associated with the Sibirian Express pattern and episodic freezing that affect species like the Texas horned lizard. Average annual precipitation varies from about 380 mm near interior scrub to over 900 mm in gulf-influenced corridors, with rainfall regimes documented by the National Oceanic and Atmospheric Administration and regional forecasts from the National Weather Service.
Geology and Soils
Underlying geology comprises Pleistocene and Holocene deposits, Pliocene Gulf Coast sediments, and localized limestone and caliche beds. Soils range from saline tidal marsh peat along Laguna Madre to clay loams and sandy loams inland, including soils classified by the Natural Resources Conservation Service as typical of floodplains and shrublands. Features such as barrier islands and tidal flats reflect sediment transport from the Mississippi River and local estuarine dynamics, with petroleum-bearing formations exploited historically by companies like Gulf Oil and modern operators regulated by the Texas Railroad Commission.
Vegetation and Habitats
Vegetation is a mosaic of mesquite thornscrub, blackland prairie remnants, coastal cordgrass marshes, mangrove stands near the Gulf of Mexico, and riparian galleries along the Rio Grande. Dominant plant taxa include Prosopis glandulosa (mesquite), Acacia rigidula (blackbrush), Spartina alterniflora in salt marshes, and isolated pockets of Quercus fusiformis (plateau live oak). Habitats support migratory corridors used by species tracked by organizations such as the Audubon Society and the National Audubon Society, and include crucial stopover sites on the Central Flyway migratory route.
Wildlife and Conservation Status
Fauna includes endemic and at-risk taxa: Northern Aplomado Falcon reintroduction projects, Ocelot populations in thornscrub, remnant Jaguarundi reports, and wintering Whooping Crane occurrences in coastal marshes. Other species include White-tailed Deer, Nilgai (introduced), migratory shorebirds like the Red Knot, and reptiles such as the Texas horned lizard. Conservation is coordinated by agencies and NGOs including the U.S. Fish and Wildlife Service, The Nature Conservancy, World Wildlife Fund, and Pew Charitable Trusts; many populations face fragmented habitat and are listed under the Endangered Species Act and state statutes administered by the Texas Parks and Wildlife Department.
Human Use and Land Management
Land uses include cattle ranching established during the Spanish colonization of the Americas and Ranching in Texas, citrus and vegetable agriculture concentrated in the Lower Rio Grande Valley, energy development from oil and gas industry activity, and coastal tourism around South Padre Island. Land management involves conservation easements administered by organizations such as the Land Trust Alliance, federal wetlands regulation under the Clean Water Act, and cross-border initiatives with Mexico addressing water rights from treaties like the Treaty of Guadalupe Hidalgo legacy and cooperative frameworks with the International Boundary and Water Commission.
Threats and Restoration Efforts
Primary threats include habitat conversion for agriculture and urban expansion in metropolitan areas like McAllen, Texas, Brownsville, Texas, invasive species such as Tamarix and Arundo donax, altered fire regimes due to suppression policies, and climate change impacts including sea-level rise affecting Laguna Madre and storm surge from Hurricane Harvey-scale events. Restoration efforts feature large-scale brush management, prescribed fire programs coordinated with the Texas A&M Forest Service, riparian restoration funded by the Natural Resources Conservation Service’s Conservation Reserve Program, and reintroduction and corridor projects led by U.S. Fish and Wildlife Service and partners like Wildlife Conservation Society.