The current biodiversity crisis has received a great deal of attention over the past two decades. As of 2006, the World Conservation Union (IUCN) found that of 40,177 species assessed using IUCN Red List criteria, 16,199 are now listed as threatened with extinction. They found that one out of every eight bird species, one out of every four mammal species, and one out of every three species of amphibians was at risk of extinction. While a number of factors have been attributed to the decline of amphibians (e.g., chemical pollution, disease, global climate change, introduction of exotic species), habitat loss and degradation are generally accepted as the main cause of this decline. Amphibians are especially sensitive to loss and degradation of habitat due to their unique life history requirements (i.e. most amphibians require both aquatic and terrestrial resources to complete their life cycle).
While there are many types of habitat loss and degradation (e.g., agriculture, land development), many studies have focused on the impacts of logging on wildlife populations and on ecosystem processes. For amphibians, much of the work has focused on pond-breeding amphibians or amphibians that do not require water for reproduction. Little information, however, exists on the effects of logging on amphibians that require streams for reproduction. In order to mitigate the impacts of habitat alteration on stream amphibians, it is necessary to have a clear understanding of the role abiotic and biotic factors play in determining habitat use and abundance. Additionally, we must determine the effects of forest management practices, such as timber harvesting, have on amphibian populations in order to develop alternative management strategies.
I have used direct (e.g., area-constrained daytime searches, visual encounter nighttime searches) and indirect (laboratory studies) methods to estimate the habitat use of stream salamanders. Specifically, I have determined the core terrestrial habitat use and the abiotic and biotic factors associated with microhabitat use and abundance, as well as determining how stream salamanders respond to predators in altered environments. Further, I have demonstrated the effects even-aged timber harvesting has on stream salamander populations and how current United States Forest Service regulations on riparian buffer widths function to protect these populations.
My data show that core terrestrial habitat use, microhabitat use, and overall stream salamander abundance are dependent on leaf litter depth and soil moisture. Furthermore, as leaf litter depth and soil moisture are reduced as a result of even-aged timber harvesting, the core terrestrial habitat use and abundance of salamanders decrease as a result of fewer microhabitats being available. The decrease in suitable microhabitats available is accompanied by a resulting increase in competition between stream salamander species. Lastly, I found that current USFS regulations for riparian buffer widths are vastly inadequate to protect stream salamander populations from activities such as timber harvesting.