Impacts of wildlife trade on terrestrial biodiversity.

The wildlife trade is worth billions of dollars annually and affects most major taxonomic groups. Despite this, a global understanding of the trade's impacts on species populations is lacking. We performed a quantitative meta-analysis of the wildlife trade that synthesized 506 species-level effect sizes from 31 studies, estimating trade-driven declines in mammals (452 effect sizes), birds (36) and reptiles (18). Overall, species declined in abundance by 62% (95% confidence interval (CI), 20 to 82%) where trade occurs. Reductions involving national or international trade were greatest, driving declines of 76% (95% CI, 36 to 91%) and 66% (95% CI, 12 to 87%), respectively. The impacts of trade were pervasive, requiring over 102 hours of travel time from settlements for trade to have no mean effect. Current protective measures fail species, with significant declines even where the harvesting for trade occurs in protected areas. Population declines tracked species threat status, indicating heightened extirpation and extinction risk in traded species. Critically, for such a severe global threat to wildlife, our analysis unearthed a limited number of studies using treatment versus control comparisons, and no studies on amphibians, invertebrates, cacti or orchids. Improved management, tackling both unsustainable demand and trade reporting, must be a conservation priority to prevent rampant trade-induced declines.