Conservation: More than half of unassessable species may be at risk of extinction

56% of species whose extinction risk cannot be assessed for the International Union for Conservation of Nature (IUCN) Red List of Threatened Species due to a lack of ecological data are likely at risk of extinction. The findings, published in Communications Biology, indicate that these species, known as Data Deficient species, may be more threatened by extinction than other species that have been assessed by the IUCN, and highlight potential biases in current conservation priorities.

Jan Borgelt and colleagues trained a machine learning algorithm to calculate the extinction risk of 26,363 species that have been previously assessed for the IUCN Red List. Calculations were based on previously published data on the geographical areas the species live in, as well as factors known to influence biodiversity, such as climate change, land use by humans, and threats posed by invasive species. The authors then used this algorithm to predict extinction risks for all 7,699 Data Deficient species.

The researchers estimate that 4,336 (56%) of Data Deficient species are likely threatened with extinction. In comparison, the IUCN Red List reports that 28% of species it has assessed are at risk of extinction. Extinction risks for Data Deficient species varied between groups and geographical areas, with 85% of amphibians, 40% of ray-finned fish, 61% of mammals, 59% of reptiles, and 62% of insects likely at risk of extinction. Land-dwelling Data Deficient species at risk of extinction typically occupy smaller geographical areas within regions such as central Africa, southern Asia and Madagascar. One third to half of Data Deficient marine species around the world’s coastlines were predicted to be at risk of extinction.

These findings highlight the conservation importance of many Data Deficient species that are likely threatened by extinction but are not classified as threatened by the IUCN. The authors suggest that more accurate assessments of these species could help shift conservation priorities and facilitate their inclusion in sustainable development goals and biodiversity targets.