The bottom-up assessment of threatened species

Identifying the percentage of endangered species is crucial for the protection of biodiversity from local to global levels. However, the high costs of species evaluation jeopardise the feasibility of evaluating all world species. We propose a model to consolidate imperfect local assessments to a first (conservative) estimation of national to global assessment. We used it for the evaluation of 8132 Belgian species starting with incomplete red lists at lower geographic levels (Belgian regions). The model is based on the logical assumption that if a species is safe («Least Concern») at local level (> 10 000 km2), then it is safe at global level. It can be used at various geographic levels to help aggregate imperfect local red lists into a first estimate of global ones. Testing the model shows that it gives very conservative results because less species are evaluated endangered at global level than when using other methods. Our model can deal with non-standard local red lists, with an error range that is reducing when local red lists become compliant with the IUCN standards. It cannot and does not aim to replace full IUCN-compliant assessments. We show the value of publishing the lists of currently safe species-not only those that are threatened. Actually, in the light of the sixth mass extinction, identifying safe species becomes as important as those that are endangered. We encourage trained biologists to evaluate less-known groups like invertebrates, algae, or microfungi. Our model facilitates a low cost first rough conservative estimate at global level. This can help historical reviews as well as identifying research and policy priorities. Our tests question the IUCN guidelines for species that are stable but only present in areas smaller than a few km2.SCOPUS: ar.jDecretOANoAutActif