Analyzing the conservation statuses of 14,669 European terrestrial and aquatic species, researchers reveal that 19% of them face extinction threats, with higher proportions observed for plants (27%) and invertebrates (24%). When extrapolated globally, these figures suggest approximately 2 million endangered species worldwide, double the previous estimate by the UN. This underscores the imperative to enhance biodiversity monitoring programs.
Given the rapid global decline in biodiversity, various international agreements and conventions (Aichi targets, UN Sustainable Development Goals, etc.) have been implemented to protect and preserve species. Specialized platforms and tools, such as the International Union for Conservation of Nature (IUCN) Red List, have been developed to assess conservation efforts’ progress. The IUCN Red List is widely recognized as a global benchmark for species conservation status.
However, assessments carry uncertainties due to data gaps, particularly regarding insects. Despite insects, which constitute 90% of invertebrates and encompass 97% of animal species, they are underrepresented in conservation data. Insects, essential for ecosystem services like pollination and decomposition, should be included in conservation efforts alongside plants and vertebrates.
Previous estimates indicated that 10% of insects were at risk of extinction. Based on data primarily from continental Europe, the new study, published in PLOS ONE, provides a more comprehensive synthesis of global biodiversity.
Under-Assessment of Insects
In Europe, the taxonomic coverage of the IUCN Red List is more comprehensive than elsewhere globally due to substantial funding contributions. The list currently includes 14,669 species, covering diverse taxonomic groups, including all European vertebrates, about 12% of plant species, and functionally important invertebrate groups (bees, butterflies, dragonflies, grasshoppers, crickets, freshwater and terrestrial mollusks, and a selection of saproxylic beetles).
Efforts have identified taxonomic groups that are generally underrepresented in conservation databases. While the assessed species were selected based on funders’ priorities, they are more diverse than those listed in international datasets like the Living Planet Index (LPI).
The new study, which the National Museum of Natural History of Luxembourg is co-leading, aims to compile all research on the IUCN Red List in Europe. It particularly catalogs species assessments until the end of 2020 to analyze distribution patterns and threats to biodiversity in Europe.
Analyses reveal that approximately one-fifth (19.4%) of the 14,669 assessed species face extinction threats (classified as critically endangered, endangered, or vulnerable). This rate is higher for plants (27%) and invertebrates (24%) than for vertebrates (18%). Axel Hochkirch, the study’s lead author and researcher at the National Museum of Natural History of Luxembourg, emphasizes that “What our study does is really highlight that insects are as threatened as other taxa. And because they are the most species-rich group of animals on our planet, this is really something which should be addressed.“
The high rate of endangered insects is attributed to recent additions to the IUCN list and a high prevalence of insufficient data. Despite the relative precision of surveys in Europe, the proportion of species with insufficient data for conservation status assessment remains relatively high (18% of known species). This deficit is particularly significant for invertebrates (24%) compared to plants (11%) and vertebrates (10%). Moreover, 60% of invertebrates have an “unknown” demographic status, according to IUCN Red List evaluators.
Global extrapolation of the analysis indicates that estimates remain largely consistent with previous assessments by other organizations, except for insects. It has been deduced that 2 million animal and plant species are at risk of extinction globally, doubling the UN’s last evaluation.
The study also confirms major decline factors reported in previous investigations. The main contributing factor is agricultural expansion, then overexploitation of natural resources, pollution, and urbanization. Overall, these factors lead to the loss and fragmentation of natural habitats. The analysis unequivocally reaffirms the extent of the impact of land-use change on biodiversity on a continental scale.
Researchers emphasize that it is not too late to strengthen and expedite conservation efforts and sustainable practices. For instance, in the Western context, reintroducing large carnivores helps balance burgeoning deer populations threatening vulnerable flora. Artificial corridors, now visible in France, mitigate the effects of habitat fragmentation on biodiversity. Agroecology is particularly promising for protecting thousands of hectares of forests and millions of insects by regenerating and safeguarding soils while ensuring long-term livelihoods.