The management of insects, diseases, fire, and grazing and implications for terrestrial vertebrates using riparian habitats in Eastern Oregon and Washington
Riparian habitats in eastern Oregon and Washington, USA compose a small percentage of the landscape, and yet these habitats are essential for many species of vertebrates. Riparian areas are sensitive to disturbance agents, which can pose a formidable challenge to effective management of these habitats. Moreover, few studies have documented the effects of disturbance agents on riparian habitats and associated fauna. In general, disturbances from insects and disease likely have strong effects on cavity nesters and insect feeders, and use of Bt (Bacillus thuringiensis) to control insect pests decreases the food supply for insectivores. Most fire effects on terrestrial vertebrates are through changes in habitat, food, and competitors, and responses to fire are variable and species specific. Salvage logging likely has negative effects for species that use dead and dying trees. Livestock grazing in riparian areas can eliminate nesting substrates, alter habitat structure and composition, compact soil, trample banks, encourage cowbird expansion, and increase exotic plants. The magnitude of these effects depends on the timing and intensity of grazing. There are almost no studies on how landscape-level vegetation patterns (including riparian corridors) contribute to the viability of wildlife populations. Managers have usually chosen to buffer riparian areas from harvest, spraying, and prescribed fire, but there are no decision-support tools or guidelines for management of riparian habitat for terrestrial vertebrates.