Climate change is expected to result in shifts in the spatial distribution of habitats and the species that occupy them, and responding to these shifts will be an important focus of applied conservation in the 21^st century.   Climate envelope models provide one tool that may be used to inform management activities relating to assessment and adaptation to future climate change.  As part of a larger effort to create climate envelope models for 21 species of threatened and endangered vertebrates occurring in southern Florida, we present a prototype model for the American crocodile (Crocodylus acutus) that illustrates both limitations and challenges associated with species distribution modeling, as well as how management recommendations can emerge from models of projected future distributions.  When modeling the contemporary climate envelope for a species, the often arbitrary selection of a geographic study area can have important implications for the differentiation of “suitable” and “unsuitable” climate space.  We compare models bounded by the entire western hemisphere with models bounded by a more realistic climate space determined by observed distributions of other New World crocodilians.  We explore projected future distributions of C. acutus in the year 2080 under high and low CO₂ emissions scenarios. 

Results/Conclusions

The high-emissions scenario projects a 70% expansion of suitable climate space for C. acutus from approximately 860,000 km² at present to 1.46 million km² in 2080.  The projected future climate envelope for C. acutus under a low-emissions scenario suggests a 45% expansion in area to approximately 1.25 million km², although the low-emissions scenario predicts a more northerly expansion of suitable climate space in Florida than the high-emissions scenario.  Both scenarios predict suitable climate space for C. acutus in Florida, but the high emissions scenario also predicts an expansion of suitable climate space into coastal portions of the northern Gulf of Mexico.  These data coupled with projections of sea level rise and land use changes provide information that will be useful in assessing the vulnerability of C. acutus to climate change and identifying opportunities for future protection for C. acutus.