Riparian Corridors
Riparian systems support high levels of biological diversity (Motroni 1980) and are among the most endangered ecosystems in the United States (NRC 1992). Native riparian plant communities comprise some of the most productive wildlife habitat in North America (Motroni 1980) and are critically important to the life cycle of endangered salmonid species (FISRWG 1998). Aquatic macroinvertebrates, required prey of salmonids, are correlated with healthy riparian forests. Riparian habitat supports over three quarters of the amphibians and half of the reptiles in California (Warner and Hendrix 1984).
Furthermore, bird species diversity is highest in riparian habitat (Leymon 1984), which is also critical habitat for neo-tropical migrant species which utilize riparian corridors as resting, foraging, and breeding grounds. Of the 502 native species of land mammals in California, approximately 25 percent are limited to or dependent upon riparian and other wetland communities. In addition, riparian systems provide habitat for over half of the species officially listed as threatened or endangered in California and are responsible for the regulation of critical ecosystem functions in adjacent aquatic environments.
Riparian corridors are dynamic, disturbance-driven ecosystems, with hydrologic processes acting as a major force in determining terrestrial plant distribution and diversity. The total species richness bears a strong relationship to the variability, quality, and distribution of the different habitat types present. Riparian zones in a near-natural state contain a relatively high diversity of landforms, vegetation types, and successional stages that are concentrated within a small geographic area. It is important to realize that under natural conditions most of the habitat diversity originates from, and is sustained by, the high frequency of flooding and erosive disturbance caused by streams. They are especially attractive to wildlife because an adequate mix of habitat types, food, and shelter is consistently available even in the face of unpredictable natural disturbances such as drought, wildfires, or severe floods.
