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Modeling pesticide risk to California gnatcatchers
Citation:
Etterson, M., N. Schumaker, K. Garber, S. Lennartz, A. Kanarek, AND J. Connolly. Modeling pesticide risk to California gnatcatchers. American Ornithological Society, Tucson, AZ, April 09 - 14, 2018.
Impact/Purpose:
Although the utility of population models for chemical risk assessment has be recognized for decades, USEPA has yet to develop and adopt a methodology for population level risk assessment for birds. We provide an integrated modeling workflow that will allow USEPA risk assessors to conduct spatially explicit population level risk assessment for pesticides in agroecosystems. This work builds on previous USEPA work integrating TIM and MCnest by including HexSim to give a spatially explicit component. The model will likely be of interest to the regulated community and to the community of scientists conducting population level risk assessment for birds.
Description:
Pesticides are used widely in US agriculture and may affect non-target organisms, including birds. Recently, USEPA has worked with other federal agencies, including USFWS and NMFS, to revise and strengthen methods for conducting pesticide risk assessments under section 7 of the U.S. Endangered Species Act. Three existing USEPA models, the Terrestrial Investigation Model (TIM), the Markov Chain Nest Productivity Model (MCnest), and the HexSim modeling environment were modified to develop an integrated model for avian pesticide risk assessment. The model is parameterized using only data currently available under the standard pesticide registration process, together with life history data available in the scientific literature. The model will be demonstrated by simulating potential pesticide effects on the federally threatened California Gnatcatcher (Polioptila californica) in the U.S. portion of the species range. Two pesticides, malathion (organophosphate), and ë-cyhalothrin (pyrethroid), applied to wheat crops under varying spatially explicit usage consistent with the labeling for the two pesticides were modeled. Model-predicted declines in gnatcatcher abundance and changes in the distribution of the species following applications of each pesticide will be highlighted. The integrated TIM/MCnest/HexSim model should allow chemical risk assessors to evaluate spatial and temporal dynamics that are important to understanding population persistence in complex spatial landscapes with multiple stressors.