Ecosystem Health: Pesticide Use from Forest Management Practices Threatens Essential West Coast Marine Organisms

March 11, 2021 | A Portland State University (PSU) study, published in Toxics, finds that pesticides from the forestry industry threaten clams, mussels, and oysters (bivalves) along the Oregon state coast. Bivalves are excellent indicator species, signaling environmental contamination through their sedimentary, filter-feeding diet. However, continuous pesticide inputs— from various forestry management regimes—into watersheds along Oregon’s coastal zone endanger these species in downstream rivers and estuaries (river mouths). Although research demonstrates many forestry practices (e.g., road building, planting, clearcutting, thinning) have cumulative effects on the ecosystem, there is a lack of studies addressing the overall impact of multiple chemical mixtures and application on watersheds and subsequent aquatic transport. The study results detect 12 different chemical compounds (two herbicides, three fungicides, and seven insecticides) in both water and bivalve samples—five of which are current-use pesticides in forest management. Although pesticide concentration and type vary by season, organism, and watershed location, 38 percent of bivalve samples harbor pesticide concentrations high enough to accumulate in tissues. Indaziflam (a current-use herbicide in Oregon forestry) is present in seven percent of bivalve samples. Furthermore, water samples find current-use herbicides, hexazinone and atrazine, and banned pesticides, like DDT/DDE, contribute to aquatic contamination downstream. [Kaegan Scully- Engelmeyer, Kaegan et al. Exploring Biophysical Linkages between Coastal Forestry Management Practices and Aquatic Bivalve Contaminant Exposure. Toxics. 9(3):46, 2021.]