Ecoregions denote areas of general similarity in ecosystems, and in the type, quality, and quantity of environmental resources. They are general purpose regions that are useful for structuring and implementing ecosystem management strategies across political boundaries (such as state lines) and across agencies. Ecoregions stratify the environment according to its probable response to disturbance, and recognize the spatial differences in the capacities and potentials of ecosystems. Ecoregion frameworks are useful for (1) inventorying and assessing national and regional environmental resources, (2) setting regional resource management goals, (3) establishing geographical research frameworks, and (4) developing regional biological criteria and water quality standards.