Oaxaca is the most floristically diverse state in Mexico, which is itself among the world’s most biodiverse countries. Varied topography and a wide range of climatic conditions undoubtedly contribute to this diversity and the State’s many endemic species, but also present challenges for modeling the potential effects of climate change on vegetation. We apply the emerging technique of exposure analysis to an updated vegetation map and different global climate models (GCMs) to predict the vulnerability of the major vegetation types found in Oaxaca. The technique uses a GIS platform to compare the present distribution of climatic conditions for the different vegetation types in their current location with projected conditions for those locations under near-future and end-of-century conditions and using two emissions scenarios. We define vulnerability as the degree of divergence between present and modeled future distributions of climate conditions where that type is found today.
Results/Conclusions:
The general trend across vegetation types and GCMs was for increased vulnerability for the end-of-century, high emissions scenario. That said, there were notable differences in the degree of vulnerability predicted for certain vegetation types and in different parts of the State. The pine-oak complexes of the central part of the State and on the Pacific slope were projected to be among the least vulnerable, while the tropical evergreen forests in the north-northeastern part of the state were projected to be most vulnerable, followed by coastal tropical dry forests. Of the major GCMs frequently used in climate modeling in Mexico, the one produced using the Reliable Ensemble Averaging method gave intermediate results, that nevertheless predicted extreme vulnerability for almost 40% of the State. These results are of particular concern in Oaxaca, where the vast majority of forests are under some form of community-based ownership/management and depended upon for a range of ecosystem services that may be threatened by the projected changes in climate.