Evaluating the impact of protected areas in lowering extinction risks in a biodiversity hotspot

The tropics harbour the highest species number on Earth, making them critical hotspots of biodiversity. However, there is an increased extinction risk towards the tropics, aka the tropical biodiversity crisis. Today, biodiversity loss is considered the main threat humanity faces. Yet, key locations may act as refugia (areas that ensure the persistence of biodiversity under environmental changes). Here, we used a set of five environmental variables (elevation, maximum temperature of the warmest month, temperature annual range, annual precipitation, and the human footprint index) to quantify the main drivers of extinction risk inside and outside protected areas for 7609 species of terrestrial animals and vascular plants distributed across Mexico. We used ordinal logistic regressions to assess drivers of extinction risk, as defined by the IUCN Red List, and evaluate the impact of the existing network of protected areas across Mexico to lower this risk. Outside protected areas, extinction risk was the highest for mammals and the lowest for reptiles. Protected areas had a positive impact by lowering the extinction risk of birds compared to outside these areas, while the opposite was observed for mammals, reptiles, vascular plants, amphibians, and arthropods. Extinction risk was greater in regions with high annual precipitation, high maximum temperature of the warmest month, low temperature annual range, as well as in areas with high elevations and human pressures on the environement. The network of protected areas in Mexico is crucial for the conservation of biodiversity; however, this network requires revision that accounts for climate change scenarios to better protect regions facing the greatest risks.