Adaptation to environmental change can carry negative externalities. We document one such case: Farmers in California respond to heat and drought by extracting more groundwater, harming access to drinking water for nearby residents. Using yearly variation we show that surface water scarcity and heat increase agricultural well construction, groundwater depletion, and domestic well failures, and that well construction accounts for a large share of the latter effects. In our setting, adaptation also exacerbates inequality. Effects on domestic well failures are concentrated in low-income and Latino communities. Climate damage estimates may be incomplete without accounting for the external costs of adaptation.

Nitrate pollution of groundwater is a pernicious issue affecting people and ecosystems in many regions of the world. Although scientists agree that nitrogen compounds from human activity enter the groundwater system, there remains a need for estimates of the causal impacts of land use on the nitrate concentrations in well water––the location where nitrate contamination has the largest impact on human health. In this paper, we provide evidence of the link between nitrate concentrations measured in well water and local land use using a dataset of repeated cross-sectional samples of about 5,000 groundwater wells and a detailed dataset of remotely sensed land uses from 2007 to 2021. Findings show that a 10 percentage point increase in the share of land use to grow high nitrogen crops within 500 meters of a well (for example, from 5% to 15% of the land surrounding a well) relative to undeveloped land leads to a 5.8% increase in nitrate concentrations within 5 to 12 years. Compare this to a 10 percentage point increase in land developed for urban use, which leads to a 1.6% increase in nitrate concentrations over a similar time frame.

Nitrate contamination of drinking water is a widespread environmental concern and threatens human health. The magnitude of the environmental health consequences depend on an individuals’ ability to avoid exposure. However, there are a number of factors which may undermine one’s ability to avoid pollution exposure. This paper studies the heterogeneity in avoidance behavior following Safe Drinking Water Act nitrate violations. I find that consumers spend approximately $4.7 million annually on bottled water and soda to avoid nitrate contaminated drinking water. However, consumers in resource-constrained areas exhibit substantially less protective behavior. This lack of averting behavior corresponds with 143 additional infant deaths per year from nitrate contamination relative to areas with less-costly access to safe drinking water. These results underscore both there are substantial costs from nitrate pollution and that these costs are disproportionately distributed to those with less ability to protect themselves.