Conservation evidence is biased but can support decision‐making for prevalent and severe threats in tetrapods

Tackling the global decline in biodiversity requires effective conservation actions to manage ongoing threats. Evidence from the success of past interventions can help identify effective actions. Such evidence‐based conservation is facilitated by searchable resources that synthesize knowledge across taxa and conditions. The existing evidence base has known taxonomic and geographic gaps, but how the diversity and prevalence of threats affecting biodiversity is represented remains unclear. We assessed the availability of evidence to address conservation threats, testing whether more evidence exists for actions tackling threats that affect more species (taxonomic prevalence) and from locations where threats are more likely (spatial prevalence). We focused on amphibians, reptiles, birds and mammals, groups with published conservation evidence synopses and completed IUCN Red List assessments listing threats. Overall, there were more studies testing conservation actions directed at more common threats (high taxonomic prevalence). Actions tackling threats linked to agriculture and exploitation of natural resources, which affect the largest number of species (34.9% and 31.0% of 35128 species, respectively), had more evidence (20.6% and 18.5% of 3662 studies, respectively). However, actions for some threats were understudied (e.g. energy production and mining), while some had more evidence than expected (e.g. invasive species). Actions targeting more prevalent threats were not identified as more effective or better understood. More studies tested conservation actions in areas where species were more likely to be impacted by threats (high spatial prevalence). However, only limited or no evidence was available for some highly impacted areas. For example, none of the 253 studies of actions addressing the impact of agriculture on birds were located in Africa, a region where 12% of the land is classed as high agriculture impact. Synthesis and applications: Despite taxonomic and spatial biases, substantial conservation evidence is available to support decision‐making by practitioners, particularly for the most prevalent and severe threats. Given the current biodiversity crisis, it is critical that this information is more widely used and that coordination among academic and practitioner partners is encouraged to evaluate current evidence and fill gaps, for example, regarding energy production and mining. A reliable and transferable evidence base is essential to effectively tackle the biodiversity crisis.