The pace of publishing IUCN Red List assessments for trees has increased dramatically, with a total of 28,676 tree assessments, 19,087 of which were published during December 2018–December 2020. Trees comprise nearly one-third of all threatened species on the IUCN Red List, and, although it is valuable to have so many tree species assessed, it is alarming that so many are at risk of extinction. Assessments for the Global Tree Assessment were undertaken by botanists worldwide, coordinated by Botanic Gardens Conservation International and the IUCN Species Survival Commission Global Tree Specialist Group following a strategic approach set out in 2015 (Oryx, 49, 410–415).
A particular focus has been to prioritize assessments of endemic tree species of the most biodiverse countries, including Brazil, Colombia, Indonesia and Papua New Guinea, and the complete assessment of all 3,118 tree species of Madagascar, of which 2,904 (93%) are endemic. The latter was a collaborative effort involving Kew Madagascar Conservation Centre, Missouri Botanical Garden Madagascar Program, the University of Antananarivo, the IUCN Species Survival Commission Madagascar Plant Specialist Group, and other botanists. Priorities for conservation have been identified, and 63% of Madagascar's endemic trees are considered threatened with extinction.
In addition to the published IUCN Red List assessments, all other tree species now have either an IUCN Red List assessment awaiting formal review, a provisional assessment or a published national or regional Red List assessment. For the first time we have a comprehensive global overview of the status of trees and of each individual species. Data already published indicate that at least 26% of the world's 58,500 tree species are threatened with extinction. The target now is to ensure that all tree species have an up-to-date assessment published by 2023.
In the meantime, the priority is to scale up conservation action for those tree species we know are threatened with extinction. A combination of ex situ and in situ approaches will be employed, with major efforts to incorporate threatened trees into ecological restoration and tree planting initiatives.