Global climate change affects organisms in all biomes and ecosystems. Two natural compensatory responses are possible. Given enough time and dispersal, species may shift to more favorable thermal environments, or they may adjust to new environments by behavioral plasticity, physiological plasticity, or adaptation. Alternatively, failure to adjust or adapt culminates in demographic collapse and extinction. Despite accumulating evidence of contemporary climate change affecting species ranges and phenologies, evidence of extinctions at either local or global scales is lacking. Here we compare recent and historical surveys for 48 Mexican species in the genus Sceloporus from 200 sites. We compared the patterns of local extinctions with temperature change derived from Mexican climatological data. We also modeled extinction risk using expected rates of temperature change from the WorldClim data base. We used this data to extend our model to lizard species worldwide.
Results/Conclusions
Our surveys revealed that since 1975 12% of local populations of Sceloporus species have gone extinct. Our global extension resulted in an estimated 4% of local populations have gone extinct worldwide between 1975 and 2009. However, by 2080 local extinctions are projected to reach 39% worldwide, and species extinctions will reach 20%. Global extinction projections were validated with local extinctions observed from 1975 to 2009 for regional biotas on four other continents confirming that lizards have crossed a threshold for climate change extinctions.
