Citation:

Bradford, D F. FACTORS IMPLICATED IN AMPHIBIAN POPULATION DECLINES IN THE UNITED STATES. Chapter 23, Michael Lannoo (ed.), Lannoo, M.J. (ed) Declining Amphibians: A United States Repsonse to the Global Problem. University of California Press at Berkeley, Berkeley, CA, , 915-951, (2005).

Impact/Purpose:

The primary objectives of this research are to:

Develop methodologies so that landscape indicator values generated from different sensors on different dates (but in the same areas) are comparable; differences in metric values result from landscape changes and not differences in the sensors;

Quantify relationships between landscape metrics generated from wall-to-wall spatial data and (1) specific parameters related to water resource conditions in different environmental settings across the US, including but not limited to nutrients, sediment, and benthic communities, and (2) multi-species habitat suitability;

Develop and validate multivariate models based on quantification studies;

Develop GIS/model assessment protocols and tools to characterize risk of nutrient and sediment TMDL exceedence;

Complete an initial draft (potentially web based) of a national landscape condition assessment.

This research directly supports long-term goals established in ORDs multiyear plans related to GPRA Goal 2 (Water) and GPRA Goal 4 (Healthy Communities and Ecosystems), although funding for this task comes from Goal 4. Relative to the GRPA Goal 2 multiyear plan, this research is intended to "provide tools to assess and diagnose impairment in aquatic systems and the sources of associated stressors." Relative to the Goal 4 Multiyear Plan this research is intended to (1) provide states and tribes with an ability to assess the condition of waterbodies in a scientifically defensible and representative way, while allowing for aggregation and assessment of trends at multiple scales, (2) assist Federal, State and Local managers in diagnosing the probable cause and forecasting future conditions in a scientifically defensible manner to protect and restore ecosystems, and (3) provide Federal, State and Local managers with a scientifically defensible way to assess current and future ecological conditions, and probable causes of impairments, and a way to evaluate alternative future management scenarios.

Description:

Factors adversely affecting amphibian populations in the US were evaluated using information from species accounts written in a standardized format by multiple authors (Volume 2 of this book). For each species, factors implicated by the authors (i.e., known or suspected) as affecting the persistence of populations were identified. Each species was also classified by status with regards to change in its historical geographic range or number of sites within the range, and region of the US. Information was sufficient to classify the status of 81 % of the 91 anuran species native to the US, and 61% of the 176 native caudate species. Species classified as Major Decline or Some Extirpations (collectively referred to as adversely affected species) comprised 49% of the anurans and 38% of the caudates. Approximately a quarter of the species were classified as No Change for both anurans (26%) and caudates (23%), and relatively few species were classified as Increase (5% of anurans and 0% of caudates). The frequency of adversely affected species was exceptionally high for ranids in the western US, whereas no differences in frequency of adversely affected anurans were evident among non-western ranids, western non-ranids, and non-western non-ranids. Specific adverse factors were identified for 58% (53) of the 91 anurans and 53% (93 ) of the 176 caudates. Of the species with adverse factors implicated, land use was the most frequently implicated for both anurans (77% of the 53 species) and caudates (91% of the 93 species). Exotic species were the second most frequently 40 - implicated adverse factor for anurans and third for caudates (IO%). Chemical contamination ranked third for anurans (I 9%) and second for caudates (I7%). Less frequently implicated factors were disease, water source modification, collecting/harvesting, and UV-B radiation. Among the anurans with adverse factors implicated, exotic species were implicated significantly more frequently in the western US (76% of 21 species) than in the other regions (16% of 32 species). Among caudates chemical contamination was implicated significantly more frequently in the non-western US (23% of 65 species) than the western US (4% of 28 species).

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