Indicators to monitor the status of the tree of life

Following the failure to fully achieve any of the 20 Aichi biodiversity targets, the future of biodiversity rests in the balance. The Convention on Biological Diversity’s Kunming–Montreal Global Biodiversity Framework (GBF) presents the opportunity to preserve nature’s contributions to people (NCPs) for current and future generations by conserving biodiversity and averting extinctions. There is a need to safeguard the tree of life—the unique and shared evolutionary history of life on Earth—to maintain the benefits it bestows into the future. Two indicators have been adopted within the GBF to monitor progress toward safeguarding the tree of life: the phylogenetic diversity (PD) indicator and the evolutionarily distinct and globally endangered (EDGE) index. We applied both to the world’s mammals, birds, and cycads to show their utility at the global and national scale. The PD indicator can be used to monitor the overall conservation status of large parts of the evolutionary tree of life, a measure of biodiversity’s capacity to maintain NCPs for future generations. The EDGE index is used to monitor the performance of efforts to conserve the most distinctive species. The risk to PD of birds, cycads, and mammals increased, and mammals exhibited the greatest relative increase in threatened PD over time. These trends appeared robust to the choice of extinction risk weighting. EDGE species had predominantly worsening extinction risk. A greater proportion of EDGE mammals(12%) had increased extinction risk compared with threatened mammals in general (7%).B.H.D. was supported by the US National Science Foundation(awards 2031928 and 2113424). W.S.L. was supported by the KEI research grant (GP2021-15). R.G. was supported by the Natural Environment Research Council Science and Solutions for a Changing Planet Doctoral Training Programme (grant number NE/L002515/1), the CASE component of which is funded by the Zoological Society of London. This paper is part of the work of the IUCN Species Survival Commission’s Phylogenetic Diversity Task Force (www.pdtf.org), a global and diverse group of experts providing guidance on the inclusion of phylogenetic diversity in conservation strategies to promote wider adoption and greater understanding of this approach by conservation practitioners, decision-makers, and the public. We thank On the EDGE Conservation for hosting and supporting our work. The views expressed in this publication do not necessarily reflect those of IUCN