The heat map and legend values represent applied toxicity as the Net Toxicity Index (NTI). Results are displayed for each study extent, a) California’s HUC8 watersheds and b) the HUC12 subwatersheds in the Bay-Delta Watershed. The NTI ranges identify the magnitude of toxicity released during pesticide applications. Credit: Parker et al., 2023, PLOS Water
Key points:
- A new tool analyzes and quantifies pesticide applications and toxicity by watershed.
- The Environmental Release Tool (ERT) was used to analyze pesticide use and quantify toxicity across 140 California watersheds.
- The results say targeting a small number of pesticides in a few watersheds can reduce aquatic toxicity in California agricultural centers.
Pesticides are a leading source of chemical hazards in environments like watersheds. Reducing the effect of pesticides requires scientists to quantify use, measure toxicity and track impacts over spatial and temporal scales. A study published in PLOS Water details a new tool developed by University of California, Santa Barbara researchers than can evaluate pesticide toxicity at high resolution.
The research group created the web and desktop application Environmental Release Tool (ERT) using watershed data from the U.S. Geological Survey. They then used ERT to analyze pesticide use across 140 California watersheds receiving agricultural pesticide applications. The ERT was able to quantify the toxicity released to aquatic taxa across these watershed areas, representing approximately 20 percent of the pesticide mass in the U.S. and covering hundreds of commodities.
Additionally, the study results from ERT reveal that small changes could have a big environmental impact. Mitigation actions on two pesticides and 16 site types would reduce about 90 percent of the toxicity to fish, aquatic invertebrates, nonvascular plants and vascular plants. Only 20 percent of the total agricultural watersheds are responsible for 80 percent of the toxicity, further supporting the idea that targeting a small number of sites could have a big effect on reducing overall applied toxicity.
“The applied toxicity of agricultural pesticides in California is dominated by a handful of pesticides, and a few crops like almonds and other nuts. Careful selection of less toxic pesticides for the same crops can drastically reduce overall applied toxicity in California, and probably around the world,” conclude the study authors.