ABSTRACT
The continuing loss of natural habitats to human settlement is the principal cause of declining biodiversity in North America and the largest impediment to conservation. Consequently, the key to effective conservation and long-term maintenance of biodiversity is habitat conservation and restoration, but in a context of sustainability and wise use (Bildstein et al., 1991; Brady, 1988; Howe, 1987; Zedler and Powell, 1993; and others). This means that many habitats, although forever altered from their natural states, are still capable of supporting rich natural biodiversity. Wetlands, because of high primary and secondary productivity, have long been attractive sites for human settlement or intense human activities, and consequently are some of the most disturbed natural habitats in North America, and the world. Howe (1987) and Dahl (1990) documented the extensive wetland losses in North America. In Mexico, habitat changes are occurring rapidly, and many of Mexico’s coastal wetlands are now degraded and severely threatened by human activities. The Río Colorado delta region (CRDR), which spans the U.S.-Mexico border, was noted by early biological explorers to have the greatest biological diversity and natural productivity in the southwestern United States and northwestern Mexico (Sykes, 1937). But today, the region may be one of the most ecologically degraded in North America.
