The number of shipments in the CITES Trade Database does not accurately reflect the volume of traded wildlife

Abstract

Volume estimation of the wildlife trade is crucial for effective biodiversity protection. Recently, Mair et al. (Biol. Conserv. 2019, 239, 108260) used the number of shipments reported in the CITES Trade Database as an estimate of the total traded volume of species to rapidly assess the appropriateness of species listings in CITES Appendices. The aims of the present study were to (1) test the presumed relationship between the number of shipments and the volume of various traded terms converted to whole organism equivalents (WOEs) and (2) compare the distribution of species in defined trade volume categories based on different calculation methods. The number of shipments did not reflect traded volume in 15% of species. Different calculation methods led to different categorisations for more than one-third of the species. In general, the number of shipments underestimates the volume of species traded in small-sized terms that allow trade in larger and less-frequent shipments and vice versa. In contrast, WOEs quantification does not consider the species that are traded in non-convertible terms (e.g., meat) or units (e.g., kilograms). Due to the structure of the data in the CITES Trade Database, it is not possible to find the only objective method of trade quantification for the whole data set. However, we recommend to use shipments approach only to exclude species with zero trade, and evaluate the real volume using WOEs where possible.