Biodiversity loss is a central issue in conservation biology, with protected areas being the primary approach to stop biodiversity loss. However, education has been identified as an important factor in this regard. Based on a database of threatened species and socio-economic features for 138 countries, we tested whether more protected areas or more education investment is associated with a lower proportion of threatened species (for different groups of vertebrates and plants). For this, we fitted generalized linear mixed-effects models (GLMM) to assess the relative importance of socio-economic variables on the proportion of threatened species. We found that education investment was negatively associated with the proportion of threatened species in 2007 and 2017, as well as with their change rates. Conversely, the percentage of protected land was significant for reptiles but showed weak relationships with other groups. Our results suggest that only increasing protected areas will not stop or reduce biodiversity loss, as the context and people’s attitudes towards wildlife also play major roles here. Therefore, investing in education, in addition to protected areas, would have the missing positive effect on achieving effective species conservation actions worldwide.