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ECOREGIONS OF TEXAS
Citation:
Griffith, G. E., S. A. Bryce, J M. Omernik, J. Comstock, A. Rogers, B. Harrison, S. Hatch, AND D. Bezanson. ECOREGIONS OF TEXAS. USGS, Corvallis, OR, 2004.
Description:
Ecoregions denote areas of general similarity in ecosystems and in the type, quality, and quantity of environmental resources. They are designed to serve as a spatial framework for the research, assessment, management, and monitoring of ecosystems and ecosystem components. Ecoregions are directly applicable to many state agency activities, including the selection of regional stream reference sites, the development of biological criteria and water quality standards, and the establishment of management goals for nonpoint-source pollution. They are also relevant to integrated ecosystem management, an ultimate goal of many federal and state resource management agencies. The approach used to compile this map of Texas is based on the premise that ecological regions can be identified through the analysis of the patterns of biotic and abiotic phenomena that reflect differences in ecosystem quality and integrity. These phenomena include geology, physiography, vegetation, climate, soils, land use, wildlife, and hydrology. The relative importance of each characteristic varies from one ecological region to another regardless of the hierarchical level. A Roman numeral hierarchical scheme has been adopted for different levels of ecological regions. Level I and Level II divide the North American continent into 15 and 52 regions, respectively. At Level III, the continental United States contains 104 regions. Level IV is a further subdivision of the Level III ecoregions. Ecological and biological diversity of Texas is enormous. The state contains barrier islands and coastal lowlands, large river floodplain forests, rolling plains and plateaus, forested hills, deserts, and a variety of aquatic habitats. There are 12 level III ecoregions and 56 level IV ecoregions in Texas and most continue into ecologically similar parts of adjacent states in the U.S. or Mexico. The map of Level III and IV ecoregions of Texas was compiled at a scale of 1:250,000; it depicts revisions and subdivisions of earlier Level III ecoregions that were originally compiled at a smaller scale. Compilation of the map poster is part of a collaborative project primarily between the the U.S. EPA National Health and Environmental Effects Research Laboratory, U.S. EPA Region VI, U.S. Department of Agriculture's Natural Resources Conservation Service, and the Texas Commission onEnvironmental Quality. This project is also associated with an interagency effort to develop a common framework of ecological regions for the US. Reaching that objective requires recognition of the differences in the conceptual approaches and mapping methodologies applied to develop the most common ecoregion-type frameworks, including those developed by the USFS and the NRCS. As each of these frameworks is further refined, their differences are becoming less discernible. Regional collaborative projects such as this one in Texas, where some agreement has been reached among multiple resource management agencies, are a step toward attaining consensus and consistency in ecoregion frameworks for the entire nation.