Banning wildlife trade is an immediate measure to protect species from overexploitation. Yet, regulations on the harvest and use of natural resources might have unintended side effects beyond the policy goals. Few causal inference studies have investigated the consequences of wildlife trade bans. We use the synthetic difference‐in‐differences causal inference approach based on an 11‐year online trade dataset to explore whether trade bans on three threatened species in Japan—giant water bugs (Kirkaldyia deyrolli), Tokyo salamanders (Hynobius tokyoensis), and golden venus chub (Hemigrammocypris neglectus)—have spillover effects on trades of substitutable nonbanned species. We found spillover effects of wildlife trade bans, leading to an increase in sales of nonbanned species in each taxon. This effect lasted over a year only for water bugs. Our results raise concerns about the unintended consequences of trade bans and underscore the importance of additional efforts concerning consumer research, monitoring and enforcement beyond the policy‐targeted species.
causal inference
,impact evaluation
,biodiversity conservation
,spillover
,wildlife trade
