The global wildlife trade involves thousands of species and is relied upon by millions of people for nutrition and income. Reconciling the demand for species with their conservation is crucial, resulting in a need for a greater understanding of the volumes in which species are traded and whether this is likely to harm their populations. Most previous work has focused on the trade patterns of specific species (e.g., pangolin spp.) or cumulative trade totals across entire taxonomic groups. The former assumes we are already aware of species that need action or study, while the latter risks obscuring species-specific deviations from the wider trend. This thesis broadly addresses the need for large-scale, species-level studies of the impacts and management of the wildlife trade. In Chapter 2, I conducted a meta-analysis of 31 studies examining the impacts of wildlife trade on terrestrial vertebrate species abundance. I found evidence of mean declines in species abundance of 62% where trade occurred relative to untraded locations, but also a swathe of systematic geographic and taxonomic biases, underpinned by great inter-specific variation in severity of impact from minimal to local extirpation. Chapters 3 and 4 focus on unpicking species-level nuance in the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) trade database, which comprehensively captures the legal international trade in CITES-listed species. In Chapter 3, I developed hierarchical Bayesian hurdle models to unpick the species-level occurrence and volumes of 1025 wild-sourced birds, mammals, amphibians, and reptiles in commercial trade. Across species and threat status (as assessed by the International Union for Conservation of Nature, IUCN), the wild-sourced trade is largely declining to absence. However, traded volumes were largely unconnected to changes in a species’ threat status, often because trade had disappeared prior to the change, but in some cases, because trade continued unchanged despite increasing extinction risk. In Chapter 4, I applied modified hierarchical Bayesian hurdle models to contrast the captive- and wild-sourced international trade in 779 commercially traded CITES-listed bird species and their relative associations with key reproductive traits. This revealed a pervasive species-level shift from wild- to captive-sourced trade, with adult survival, age at first reproduction and longevity reproductive traits associated with captive trade volumes. In combination, the results across the thesis highlight the critical importance of species-specific data to generate informed conclusions on trade, with impacts, volumes, and trends varying by orders of magnitude for both closely related and demographically similar species. Integrating transparent assessments of sustainability into CITES processes is key to both protecting species and ensuring a future for sustainable use and trade.
