Résumé
The likelihood and magnitude of the impacts of climate change on potential vegetation and the water cyclein Mesoamerica is evaluated. Mesoamerica is a global biodiversity hotspot with highly diverse topographicand climatic conditions and is among the tropical regions with the highest expected changes in precipitationand temperature under future climate scenarios. The biogeographic soil-vegetation-atmosphere modelMapped Atmosphere Plant Soil System (MAPSS) was used for simulating the integrated changes in leaf areaindex (LAI), vegetation types (grass, shrubs, and trees), evapotranspiration, and runoff at the end of thetwenty-first century. Uncertainty was estimated as the likelihood of changes in vegetation and water cycleunder three ensembles of model runs, one for each of the groups of greenhouse gas emission scenarios (low,intermediate, and high emissions), for a total of 136 runs generated with 23 general circulation models(GCMs). LAI is likely to decrease over 77%-89% of the region, depending on climate scenario groups,showing that potential vegetation will likely shift from humid to dry types. Accounting for potential effects ofCO2 on water use efficiency significantly decreased impacts on LAI. Runoff will decrease across the regioneven in areas where precipitation increases (even under increased water use efficiency), as temperaturechange will increase evapotranspiration. Higher emission scenarios show lower uncertainty (higher likelihood)in modeled impacts. Although the projection spread is high for future precipitation, the impacts ofclimate change on vegetation and water cycle are predicted with relatively low uncertainty.