The Time-varying Costs of Invasive Species: An Application to Wild Pig Damages in US Cropland Agriculture

Invasive species like wild pigs (WPs) inflict substantial economic losses on agricultural systems but accurately quantifying these costs is challenging due to limited data on population abundance. In the absence of data on species abundance, researchers frequently rely on species occurrence data for estimating economic impacts. We develop a conceptual model illustrating that stock dynamics lead to time-varying costs of invasions that bias occurrence-based estimates using two-way fixed effect (TWFE) methods. Then, we estimate the welfare cost to cropland agriculture of WP invasions in the southeastern US by combining more than a decade of data on the presence of WPs with land rental market and cropland data. We find that WPs cost an average of 1.6 million dollars per county per year (95% CI: $1.1 million to $2.1 million). Estimates using TWFE underestimate total costs by 21% of the unbiased estimate. The difference is driven by a 33% underestimate of impacts to cash rent with the arrival of WPs. We also provide evidence that producers adapt to WPs by planting fewer acres of corn and soy and more acres of cotton and sorghum. Our estimates support the need for targeted, effective WP elimination strategies in the US.