Katie Fellows

Project title: Climate change, pesticide use, and exposure disparities in agricultural communities: A case study of almond orchards in California

Degree: PhD | Program: Environmental and Occupational Hygiene (EOHY) | Project type: Thesis/Dissertation
Completed in: 2019 | Faculty advisor: Edmund Y. W. Seto


Anthropogenic climate change is expected to influence pest dynamics and pesticide application timing and rate, but little research has attempted to quantify the relationship or associated health impacts. Changing pesticide applications will impact risk of human exposure, particularly in agricultural communities. A multi-disciplined analysis method is presented here that assesses the association between climate change and agricultural pesticide use, utilizing a combination of climate science, ecological assessment, and public health methods to examine how pesticide use has and is expected to increase with climate change, and what that entails for human health. Presented here is a spatial and temporal assessment of the impacts of climate change on insecticide use and human health in the California Central Valley. Historical climate data was utilized to estimate degree-days and pest generations for economic pests of concern on the almond crop. Statistically downscaled climate model projections were then used to calculate pest dynamics through 2099. Results indicated an increase of one to two full generations for both pests considered in the analysis by the end of the century. Pesticide use reports were next assessed for trends in insecticide use as well as correlation with degree-days and climate. The modelled relationship was applied to climate projections to project insecticide use through 2099. Insecticide use was found to have a strong seasonal trend, with most applications occurring in the southern region; use was projected to increase throughout the entire valley by the end of the century. A geospatial assessment of insecticide use intensity and demographics was then used to characterize populations that are more likely to be exposed to insecticides in the Central Valley. This assessment maps areas with the greatest risk of exposure potential, based on use intensity and proximity to orchards, and identifies areas that are disproportionately impacted based on social vulnerability indicators. Those living in the southern region of the valley were found to be at greatest risk of exposure, and these same communities were also found to be the most socially vulnerable. By understanding how climate change impacts vulnerable communities and human health, we can mitigate future exposure and reduce pesticide-induced disease.