Banning wildlife trade can boost demand for unregulated threatened species

Natural resource regulation might have unintended spillover impacts beyond the policy targets. Banning wildlife trade is an immediate measure to protect species from overexploitation. However, few causal inference studies have investigated the consequences of wildlife trade bans. We use the synthetic difference-in-differences approach to causal inference based on a 10-year online auction dataset to explore whether trade bans on three threatened species in Japan–giant water bugs, Tokyo salamanders, and golden venus chub–have spillover impacts on trades of substitutable non-banned species. We find adverse conservation impacts of wildlife trade bans, leading to an increase in trade volume of non-banned species in each taxon although there are heterogeneity effects across taxa. Our results raise concerns about the unintended consequences of trade bans and restate the importance of further efforts around consumer research, monitoring and enforcement beyond the target species, while minimizing costs by applying modern technologies and enhancing international cooperation.