Banning wildlife trade can boost demand for unregulated threatened species

Regulation of natural resource use might have unintended spillover impacts beyond the policy targets. Overexploitation is a major cause of species extinction and banning wildlife trade is a common and immediate measure to tackle it. However, few rigorous studies have investigated consequences of wildlife trade bans, and those few studies have focused only on the policy target species. This means governments and researchers may have overlooked side effects of trade bans on unregulated threatened species. This study explores whether trade ban regulations on three threatened species (i.e., giant water bugs Kirkaldyia deyrolli, Tokyo salamanders Hynobius tokyoensis and golden venus chub Hemigrammocypris neglectus) have spillover impacts on the demand for non-banned species considered as substitutes. We draw on a 10-year online auction dataset and the recently developed causal inference approach—synthetic difference-in-differences—to analyze the trade ban regulation implemented in February 2020 in Japan, one of the largest wildlife trade markets. The results show that bans on the giant water bugs and Tokyo salamanders led to an increase in the trade of non-banned species, whereas there was no such evidence concerning the golden venus chub. The findings suggest that policy evaluations ignoring spillover effects might overstate the benefits of trade bans. Our findings raise concerns about the unintended consequences caused by trade bans and restate the importance of further efforts around consumer research, monitoring and enforcement beyond the species targeted by policies, while minimizing the costs by applying modern technologies and enhancing international cooperation.