Charles A Taylor

Pesticides are linked to negative health outcomes, but a causal relationship is difficult to establish due to nonrandom pesticide exposure. I use a peculiar ecological phenomenon, the mass emergence of cicadas in 13 and 17-year cycles across the eastern half of the US, to estimate the short and long-term impacts of pesticides. With a triple-difference setup that leverages the fact that cicadas only damage tree crops and not agricultural row crops, I show that insecticide use increases with cicada emergence in places with high apple production. Exposed cohorts experience higher infant mortality and adverse health impacts, followed by lower test scores and higher dropout rates. I exploit geo-spatial sources of variation and find evidence for pesticide exposure through a water channel. Moderate levels of environmental pollution, not just extreme exposure, can affect human health and development. The study design, which encompasses the entire chemical era of US agriculture since 1950, provides insights into the regulation of pesticides in the US and globally.

Post-war growth in agricultural productivity outpaced the US non-farm economy, spurred by steadily increasing crop yields. We argue that rising atmospheric CO₂ is responsible for a significant share of these yield gains. We present a novel methodology to estimate the CO₂ fertilization effect using data from NASA’s Orbiting Carbon Observatory-2 (OCO-2) satellite. Our study complements the many field experiments by regressing county yields on local CO₂ levels across the majority of US cropland under actual growing conditions. For identification, we utilize year-to-year anomalies from county-specific trends, an instrument for those CO₂ anomalies using wind patterns, and a spatial first-differences approach. We consistently find a large CO₂ fertilization effect: a 1 ppm increase in CO₂ equates to a 0.4%, 0.6%, 1% yield increase for corn, soybeans, and wheat, respectively. In a thought exercise, we apply the CO₂ fertilization effect we estimated in our sample from 2015-2021 backwards to 1940, and, assuming no other limiting factors, find that CO₂ was the dominant driver of yield growth–with implications for estimates of future climate change damages.

Human actions can alter the local and regional climate, particularly via land use. We assess the impact of the Great Plains Shelterbelt, a large-scale forestation program in the 1930s which planted 220 million trees across six US Midwestern states. The program led to a regional increase in precipitation and decrease in temperature, with impacts persisting for several decades. The change in climate extended to adjacent unforested land up to 200km away—enabling us to directly study climate adaptation. In places facing more favorable growing conditions, crop yields increased by 43%. Adaptation accounts for up to half of the yield increase, with farmers switching to more water-intensive production. This paper highlights the endogeneity risk in using spatial variation in climate trends in estimating climate damages, as well as the potential for tree planting to mitigate climate change impacts.

As the largest user of global water, irrigated agriculture accounts for 20% of global cropland and 40% of food production. Irrigation is also a potential adaptive response to drought and extreme temperatures. This paper examines the extent to which the current global irrigation footprint reflects climate change over the last 50 years. Utilizing exogenous variation in geological structure, I find evidence that farmers adapt by increasing irrigation in places that became dryer and hotter. The results hold globally and in the US. Observed recent warming is responsible for 9% of global irrigation growth. GRACE satellite data shows that climate-driven irrigation contributes to aquifer stress, as well as increased soil salinity, thus representing large negative externalities of adaptation to climate change and a potential threat to future food security.

Fertilizer is a major source of water pollution that causes widespread algal blooms and threatens aquatic ecosystems. Driven by agriculture, the benefits of fertilizer accrue to farmers but the costs are borne to downstream water users. The negative externality has yet to be quantified at a large scale in the US, partly because most farm pollution is unregulated under the Clean Water Act, and partly due to the lack of temporally-consistent, administrative-level water quality data. This study utilizes a long-term satellite-derived measure of algal bloom intensity that encompasses lakes, rivers, and coastal areas. We find a significant negative economic impact of algal blooms in locations downstream from agricultural areas, as well as in water-reliant regions (e.g., coastal areas) and economic sectors (e.g., fishing, tourism, recreation). The reduction in income extends for up to four years following high intensity algal blooms. From these results, we estimate the external cost of nitrogen fertilizer to be $580 per ton, or 66% of its 2020 market value.

In 2020 the EPA narrowed the definition of ‘Waters of the United States’, significantly limiting wetland protection under the Clean Water Act. Current policy debates center on the uncertainty around wetland benefits. We estimate the value of wetlands for flood mitigation across the US using detailed flood claims and land use data. We find the average hectare of wetland lost between 2001 and 2016 cost society $1,840 annually, and over $8,000 in developed areas. We document significant spatial heterogeneity in wetland benefits, with implications for flood insurance policy and the 50% of ‘isolated’ wetlands at risk of losing federal protection. (ungated) (replication)

Policy responses to the COVID-19 outbreak must strike a balance between maintaining essential supply chains and limiting the spread of the virus. Our results indicate a strong positive relationship between livestock-processing plants and local community transmission of COVID-19, suggesting that these plants may act as transmission vectors into the surrounding population and accelerate the spread of the virus beyond what would be predicted solely by population risk characteristics. We estimate the total excess COVID-19 cases and deaths associated with proximity to livestock plants to be 236,000 to 310,000 (6 to 8% of all US cases) and 4,300 to 5,200 (3 to 4% of all US deaths), respectively, as of July 2020, with the vast majority likely related to community spread outside these plants. The association is found primarily among large processing facilities and large meatpacking companies. In addition, we find evidence that plant closures attenuated county-wide cases and that plants that received USDA permission to increase their production-line speeds saw more county-wide cases.

Fertilizer is critical to agricultural supply chains, but its use results in downstream externalities in the form of aquatic hypoxic zones and algal blooms. Quantifying farm pollution is challenging due to its non-point nature and the lack of a temporally consistent, administrative-level dataset on water quality. This study offers a novel satellite-derived measure of algal bloom intensity that spans 30-plus years and encompasses lakes, riparian, and coastal aquatic resources across US counties. We show that fertilizer use is closely linked to our measure of water quality. Such farm pollution drives water quality impairment both locally and downstream from the fertilizer use, with impacts occurring at an annual and longer-term timescale.

Agricultural land use has recently peaked, both globally and across country income groups, after centuries of expansion and intensification. Such shifts in the evolution of global land use have implications for food security, biodiversity loss, and carbon emissions. While economic growth and land use are closely linked, it is difficult to determine the extent to which the relationship is causal, deterministic, and unidirectional. Here we utilize gridded datasets to study long-term global land use change from 1780-2010. We find evidence for an economic tipping point, where land use intensifies with economic development at low income levels, then reverses after incomes reach a critical threshold. Cropland peaks around $5,000 GDP per capita then declines. We utilize a Markov model to show that this reversal emerges from a variety of divergent land use pathways, in particular the expansion of protected areas and a reduction in land use lock-in. Our results suggest that economic development remains a powerful driver of land use change with implications for the future of natural ecosystems in the context of continued population and income growth.

Conflict, drought and locusts are leading concerns for African food security but the relative importance and spatiotemporal scale of crises resulting from each hazard is poorly characterized. Here we use continuous, subnational data to demonstrate that the rise of food insecurity across sub-Saharan Africa that began in 2014 is attributable to an increase in violent conflict, particularly in South Sudan and Nigeria. Although drought remains a leading trigger of food crises, the prevalence of drought-related crises did not increase from 2009 to 2018. When exposed to drought, pastoralists experienced more widespread, severe and long-lasting food crises than people living in agricultural zones. Food insecurity remained elevated in pastoral regions for 2 years following a drought, while agricultural regions returned to pre-drought food-security levels in ~12 months. The few confirmed famines during the 2009–2018 period coincided with both conflict and drought, while locusts had little effect on food security during this period.

Past pandemic experience can affect health outcomes in future pandemics. This paper focuses on the last major influenza pandemic in 1968 (H3N2), which killed up to 100,000 people in the US. We find that places with high influenza mortality in 1968 experienced 1-4% lower COVID-19 death rates. Our identification strategy isolates variation in COVID-19 rates across people born before and after 1968. In places with high 1968 influenza incidence, older cohorts experience lower COVID-19 death rates relative to younger ones. The relationship holds using county and patient-level data, as well as in hospital and nursing home settings. Results do not appear to be driven by systemic or policy-related factors, instead suggesting an individual-level response to prior influenza pandemic exposure. The findings merit investigation into potential biological and immunological mechanisms that account for these differences—and their implications for future pandemic preparedness.