Predicting biodiversity loss in terrestrial vertebrates: A global analysis of Red List Index trends and key drivers (2002–2021)

The Red List Index (RLI) serves as a vital indicator of extinction risks, where a hypothetical value of 1 implies no species are threatened, and 0 implies all species have gone extinct. Despite its importance, no prior country-level studies have analyzed factors predicting RLI trends over time. This study employs mixed-effect regression models to examine extinction risk trends across 193 countries from 2002 to 2021, incorporating factors such as the year of publication of a country's National Biodiversity Strategic and Action Plan (NBSAP), indigenous land hold/use, globalization, GDP per capita, population density, World Bank region, and island status. Initial 2002 RLI values emerged as the most significant predictor of extinction risk trends, suggesting potential biodiversity degradation cascades. After adjusting for key covariates, a 10-year lagged NBSAP publication was linked to a modest reduction in the average annual RLI decline, from −0.013 to −0.012. Island nations are particularly vulnerable, with extinction risks increasing 2.6 times faster than in mainland countries. While population density and GDP per capita correlated negatively with RLI trends, indigenous land hold/use emerged as a significant positive factor. Globalization (a weighted social, economic, and political index) had a slightly positive impact for mainland countries but was substantially negative for islands, likely due to invasive species. If current trends persist, many countries could face near-total species extinction within 400 years. This research underscores the urgent need for comprehensive conservation efforts to protect the billions of years of evolutionary history at risk. • Extinction risks declined from −0.13 to −0.12 annually after NBSAP publication. • Per capita GDP ties to higher extinction risks, especially in South Asia. • Island nations' extinction risks accelerated 2.5 times faster than non-island states. • Globalization linked to drastically faster extinction risk acceleration on islands. • Indigenous land hold/use associated with lower extinction risks.