Pesticide use may be influencing wild bee population decline: Study

The widespread use of pesticides may be contributing to the sharp decline in wild bee populations, a new study has found. While there are many reasons for the global bee population downswing, the surging application of two specific pesticides has been particularly influential in these dynamics, according to the study, published Tuesday in Nature Sustainability. Those two compounds, neonicotinoid and pyrethroid, have become “a major driver of changes in occupancy across hundreds of wild bee species,” the authors explained. For certain species, that change has been so significant that high pesticide use is contributing to a 43.3 percent decrease in the likelihood that a species will inhabit a particular location, per the study. To draw their conclusions, a University of Southern California-led research team inspected museum records, ecological surveys and community science data from the contiguous U.S., collected between 1996 and 2015. They then sifted through more than 200,000 unique observations of more than 1,000 species, which represent about a third of all known U.S. bee species, to determine how often different species inhabited various locations. In conjunction with these assessments, the researchers also analyzed government data on crop cover types and county-level pesticide application. “Across the contiguous United States, we found that higher pesticide use resulted in lower occupancy of wild bees,” the researchers stated. “The negative effect of pesticide use was consistent across all five families of bees.” The authors cited their findings as a compelling argument in support of alternative pest control strategies. They particularly touted the benefits of integrated pest management, which involves the deployment of natural predators, proactive efforts to reduce pest establishment and physical traps and barriers. The new study’s results build upon previous research led by the same team, who identified the flawed nature of current ecological risk assessments when it comes to pesticides and bees. In that study, they found that these assessments, which usually rely on honeybees — an invasive species — as a proxy for all bees, are underestimating the threat to wild ones by as much as a millionfold. “When we only focus on the western honeybee, we’re ignoring the unique responses of other wild bee species to pesticide exposure,” lead author Laura Melissa Guzman, an assistant professor of biological sciences at the sUniversity of Southern California, said in a statement. “More data and analysis on the long-term effects of pesticides will help guide these efforts to the benefit of all pollinators, including wild bees,” she added.