Red Listing the world’s tree species: a review of recent progress

Abstract

The IUCN (International Union for Conservation of Nature) Red List of Threatened Spe- cies™ (RL) is widely recognised as an authoritative assessment of the conservation status of species, yet its coverage is uneven and incomplete. Trees account for approximately 20% of taxa currently included, but most of these were listed a decade ago. Over the last 10 yr, only 879 taxa have been added to the RL database, representing 11% of the number listed in 1998. However, progress has not been as limited as these data suggest. Ten recent assessments of different groups of trees are pro- filed, and the lessons learned from these assessments are summarised. In total, these assessments have evaluated >2500 tree taxa, but only a fraction of these have been added to the RL database, rais- ing concerns about the process of data management. Results indicated that a mean of 42% taxa were classified as threatened. Information on the status and distribution of most tree species is severely lacking, a situation compounded by taxonomic confusion in many groups. As a result, RL assessments will continue to be highly dependent on expert knowledge originating from herbarium data, which, as demonstrated here, tends to result in a relatively high proportion of taxa being listed under RL Cri- teria B1 and B2. Given this situation, attempts to use the RL to support global monitoring of biodiver- sity appear premature, and much greater support needs to be given to collection of primary field data and expert knowledge to accurately ascertain the current status of the world's threatened tree spe- cies.