More than one-half of the wetland habitats in the continental United States have disappeared. Land use changes have resulted in similar losses of coastal wetlands in Texas. Almost two-thirds of hardwood bottomlands (one of the more important habitats) are now gone. In the lower Rio Grande Valley, more than 95 percent of native brush has vanished. Native longleaf pine forests have declined from an estimated six million acres to less than one million acres. Some 95 percent of the originally occurring native prairies have also disappeared.

Remaining habitats have suffered too. Human development has fragmented them. Poor land management practices have modified them. And the introduction of exotic plants and animals has displaced native species.