The role of contaminants and pollution in species decline

Members of over 1,200 taxa have been listed as Threatened or Endangered, and over 4,000 additional organisms have been identified as Candidate Species or Species of Concern. Both naturally-occurring and anthropogenic activities (e.g., environmental contaminants and pollution) have been demonstrated to be a significant factor in depressing populations or catalyzing the final crash of some species. The objective of this project is to develop a synthesis document and database that lists and ranks the presumed causes of decline, with special emphasis on contaminants and pollutant-related situations. This will be accomplished by a synoptic review of all recovery plans (n=517) with listing packages (n= 1180) serving as a secondary source of information, followed by itemization, cross-referencing, enumeration, and ranking of contributing and limiting factors. To date we have analyzed most of the available recovery plans for freshwater mussels (n=39), reptiles (n=26). and amphibians (n=6). We categorized 116 reasons fur the decline in freshwater mussels, subsuming them into 6 classes: habitat alteration/availability (44.4%);.contaminants (24.1%); pollution (18.0%); exploitation/harvest (1.7%); introduction of exotic species (2.7%); miscellaneous others (9.2%). The 171 causes of decline for reptiles can be subsumed into the same categories: habitat alteration/availability (32.7%); contaminants (6.4%); pollution (9.9%); exploitation/harvest (28.7%); introduction of exotic species (11.1%); miscellaneous others (11.1%). The 34 causes for amphibian decline fall into 5 classes: habitat alteration/availability (50.0%); contaminants (5.9%); pollution (5.9%); exploitation/harvest (5.9%); miscellaneous others (32.3%). The contaminant and pollution related causes for the decline in mussels can be attributed to four classes of alterations: water quality (47.2%); effluents/ spills (46.7%); biocides (3.3%); other toxic compounds (2.8%). For reptiles, the contamination and pollution factors can also be divided similarly: water quality (2.0%); effluents/spills (51.0%); biocides (27.5%); other toxic compounds (19.6%). The amphibian data yields comparable results: water quality (16.67%); effluents/spills (16.67%); biocides (33.33%); and other toxic compounds (33.3%) as causes affecting amphibian decline. The applicability of these data is extensive. including facilitating reviews of Section 7 consultations and Environmental Impact Statements, reviewing permit applications, conducting environmental contaminant risk assessments, identifying specific data gaps and research needs, selecting potential management actions, and establishing priorities fur broad-based research on limiting factors applicable to groups of species rather than the current species-by-species approach. However, caution must be exercised in the use of these data because of the speculative nature of the causes; most of the causes (66.5%) are based on poorly documented expert opinion and/or guesswork. This is particularly true of the contaminant/pollution categories where only 17.6% of the incidents are documented in the literature.