Conference Agenda

North America has lost nearly three billion birds since 1970, with grassland obligates ac counting for the steepest decline at 53% (Rosenberg et al., 2019). While ecological studies have attributed these losses to habitat conversion and pesticide exposure, the role of upstream economic drivers (in particular trade policy) has not been causally established. This paper exploits the staggered Canada-US (CUSFTA, 1989) and US-Mexico (NAFTA, 1994) agricul tural tariff elimination schedules, with crop-specific zero-tariff dates spanning 1990 to 1998 on the relevant bilateral margin. Combining stop-level Breeding Bird Survey data on 838 sites with a Bartik-style continuous exposure measure and a Sun-Abraham staggered difference-in differences estimator, we identify the effect of trade-induced crop reallocation on local avian bio diversity. We find that NAFTA exposure caused a 4 to 9% decline in local species richness over five years, rising to 10 to 12% in areas dominated by the soybean cohort. Effects are concen trated on grassland obligate species; generalist species, which would be the most direct margin for a pesticide-mediated channel, show no significant response. This habitat-specific pattern, combined with a contemporaneous-only pesticide response that fades within three years, iden tifies land-cover simplification rather than chemical intensification as the operative mechanism. The findings establish the first causal estimate of an agricultural trade liberalization’s effect on local avian diversity in a developed exporting economy, identified through the staggered tariff phase-out of NAFTA/CUSFTA.