A framework for measuring national trends in the extinction risk of evolutionarily distinct species using the EDGE Index

Abstract

The biodiversity crisis is threatening evolutionarily distinct species, those that constitute long periods of unique evolutionary history or that are from highly imperilled lineages. The EDGE (Evolutionarily Distinct and Globally Endangered) index was designed to track the changing extinction risks of these species and is listed as an indicator in the Kunming-Montreal Global Biodiversity Framework. Here, we provide a set of guidelines for calculating the EDGE index at the national level and for addressing data uncertainty. We distinguish two approaches for calculating a country-level EDGE index, either generated directly by using national data or from disaggregated global data. Using two national Red Lists, we show the contrasting state of high evolutionarily distinct nesting birds across French territories, and the elevated threat status of high evolutionarily distinct endemic species for South African vertebrates. Using global extinction risk data, we then reveal the deteriorating state of birds, mammals, and amphibians over time, and we highlight the countries with the highest proportions of threatened evolutionarily distinct species. Application of these guidelines should aid countries in monitoring their evolutionarily irreplaceable species, which in turn can help target local conservation actions, while contributing to global efforts to preserve the tree of life.