Raising awareness through the Global Tree Assessment: Extinction risk of six fully assessed tree groups

Abstract

Societal Impact Statement: Trees are essential to life on earth—playing important economic, ecological and cultural roles. However, the world is facing a biodiversity crisis, and to be able to effectively conserve tree species with limited funds, we need to know which tree species are threatened. The Global Tree Assessment has addressed this gap in knowledge through accelerating the production of International Union for Conservation of Nature (IUCN) Red List assessments. Analysing the results of completed taxonomic groups allows for targeted conservation. Here, we explore the extinction risk of six understudied genera with ethnobotanical uses, allowing for conservation priorities to be set. Summary: To highlight the ongoing progress of the Global Tree Assessment, a synthesis of the International Union for Conservation of Nature (IUCN) Red List data has been produced for six genera (Gilbertiodendron, Humiriastrum, Liquidambar, Nectandra, Teijsmanniodendron and Tilia) which have all their tree species assessed. This was used to analyse the extinction risk within these groups with the aim of setting conservation priorities and raising awareness of genera not previously publicised in the Global Tree Assessment. The genera were chosen based on completeness, in terms of number of tree species with published IUCN Red List assessments. IUCN Red List categories, threats and uses from each species' IUCN Red List assessment were analysed. An ex situ survey was also carried out to identify species found in botanic gardens, arboreta and seed banks. Higher threat levels were found in the predominately tropical genera (Gilbertiodendron, Humiriastrum, Nectandra and Teijsmanniodendron) compared with the broadly more temperate genera (Tilia and Liquidambar). Habitat loss due to agriculture is a major threat in all genera with exploitation also a key threat to Gilbertiodendron and Tilia. Gilbertiodendron, Humiriastrum, Nectandra and Teijsmanniodendron have no threatened species conserved in ex situ collections. We have identified a need for a range of conservation measures, including collecting threatened species of these groups for ex situ conservation, to ensure no species becomes extinct.