Upwind land-use change impacts on wetland vulnerability

Research on the protection and preservation of wetlands has traditionally focused on direct human drivers and impacts of climate change occurring in their upstream hydrological basin. However, since precipitation falling in the hydrological basin comprises both oceanic and terrestrial evaporation originating mostly outside of the basin boundaries, upwind land use and hydroclimatic changes affecting this supply of precipitation also need to be assessed. This study assesses the vulnerability of 40 wetlands of international importance to land use and hydroclimatic changes occurring upwind (i.e., in their precipitationsheds). We here use a dataset containing atmospheric moisture flows in combination with evaporation from natural and current vegetation to analyse the impact of extra-basin vegetation changes on the precipitation over the wetland basins. The analysis shows that historical land-use conversion has already caused reduced incoming precipitation into most wetland hydrological basins. The strongest effects are seen in (sub)tropical wetlands in South America, Africa and Asia and especially those located downwind of large agricultural areas. Based on our results and current wetland decline rates, we find that wetland sites in China, India, South America and Sub-Saharan Africa are especially threatened by hydroclimatic and vegetation changes outside of their basins. Additionally, larger basins appear to be more reliant on evaporation from within their basin boundaries than smaller hydrological basins. Using wetland ecosystems as an exemplary case, this study stresses the need to incorporate downwind effects to land-use changes in sustainable ecosystem management approaches. Since the transition from potential natural vegetation to agricultural land is often associated with changes in evaporation, land conversion may affect the resilience of wetland water availability. Following this analysis of the upwind moisture sources of wetland basins, future studies should investigate the potential effect of wetland loss on downwind precipitation patterns.