Global convergence of rainfall-streamflow regulation by natural forests

Abstract:

Vegetation interacts with the hydrological cycle at multiple scales. Forests, in particular, have been recognized to influence the water cycle through multiple processes that interact at different spatial and temporal scales. This issue has precluded a comprehensive theory around vegetation-water interactions. A fundamental ecohydrological process of both scientific and societal relevance is the conversion of rainfall into runoff. This is particularly important in the context of global change, where not only climate forcing is altered, but also surface characteristics that determine this process (such as vegetation cover) are significantly altered. To assess whether the effect of forest cover on rainfall-runoff and streamflow regulation exhibits general behavioral patterns, related the presence and amount of forest cover with the dynamics of long-term precipitation and streamflow information for 22 sub-basins associated with 9 large basins of global importance. We found that sub-basins with high forest cover exhibit a strong long-term capacity to regulate the conversion of rainfall into runoff. Notably, this capacity is independent of forest type, climate regime, basin size and geographic location. Our results indicate a potential cross-scale effect of forest cover on the water cycle that is associated with local-to-regional ecological processes in forests that enhance their potential to regulate the water cycle in multiple scales. Further, our results highlight the potential effects of ongoing global forest loss, particularly fast in tropical regions, on the sustainability of provisioning and regulating ecosystem services in river basins.