Western pond turtles in Sequoia National Park and other California remote wildlands have been exposed to an assortment of agricultural and industrial contaminants, including some that aren’t currently in use, a new study shows.
Scientists sampled for 57 compounds, including pesticides, in turtles, invertebrates, and sediments from three sites: Sequoia National Park, Whiskeytown National Recreation Area, and Six Rivers National Forest.
None of the turtles at any of the sites carried pesticides currently in use, only those used in previous decades. However, both current pesticides and those used in the past were prominent in sediments and in the insects, snails, and mollusks that turtles eat at Sequoia National Park, which is immediately downwind of Central Valley agriculture.
Previous studies have linked pesticide use upwind of Sequoia National Park to the disappearance of a rare frog species, the foothill yellow-legged frog. Also, a 2013 study found that turtles in Sequoia National Park had signs of physiological impairment consistent with pesticide exposure.
“Pesticides don’t recognize boundaries,” says Brian Todd, associate professor of wildlife, fish, and conservation biology at University of California, Davis, and coauthor of the study that is published in the journal Chemosphere.
“Even though we think of national parks as being protected from conservation threats like development, they’re not immune from pesticides and global contaminants that cross park borders.”
Western pond turtles can be key indicators of exposure to environmental contaminants. They tend to accumulate contaminants due to their long life spans—they can live 50 years or more—and their generalist diets, make it easier for scientists to track a lifetime of exposure.
While researchers studied nine common pesticides, there were nearly 900 active ingredients applied to agricultural lands in California during the study. The interactions of those ingredients are not well understood.
“We need more information on how these compounds interact and how they affect non-target organisms,” Todd says. “Then we can continue to refine the types of pesticides used so they have fewer and fewer unintended consequences.”
Other researchers from UC Davis and from Oregon State University are coauthors of the study that was funded by the US National Park Service.
Source: UC Davis