Global patterns and drivers of the Anthropocene defaunation crisis

My research revealed that 48% of animal species are declining in population sizes, 49% are stable, and only 3% are increasing, Additionally, 33% of species categorised as non-threatened are declining. Integrating conservation categories with population trends revealed that 23% of vertebrates globally are at the highest risk of extinction (threatened declining), primarily in the tropics. Life history traits played a role in the declines of non-threatened vertebrates, while anthropogenic threats influenced taxon-dependent stages.

Moreover, only 2% of threatened vertebrates are experiencing population stability or increase. We revealed that the number of species on the verge of becoming categorised as threatened (1,830 Near Threatened declining species) is 31-fold higher than the number of species on the verge of becoming non-threatened (59 Vulnerable increasing species). Based on this latent extinction risk, we revealed that extinction risk hotspots are predicted to expand in geographic magnitude across each vertebrate taxonomic class.

For amphibians in particular, we revealed 41% of species are at the highest extinction risk (threatened declining), predominantly in the Neotropics and Sri Lanka. Life history traits influenced declines in non-threatened species, while environmental factors influenced declines in threatened species. Finally, our assessment of the role of UV-B in amphibian extinctions revealed that increasing UV-B radiation predicted the likelihood of being both threatened and declining for temperate salamanders, while decreasing UV-B predicted declining population sizes for temperate frogs and low elevation tropical frog species.

Overall, this thesis suggests that our understanding of biodiversity loss is underestimated when using conservation categories alone. The integration of extinction risk proxies provides a nuanced identification of species on the brink of extinction, aiding to anticipate potential oncoming crises in certain taxa and factors contributing to this increasing risk, offering a pre-emptive approach for conservation.