Prototype of a global model for regulating ecosystem services of inland wetlands

Natural wetlands deliver a range of ecosystem services like water, food and fibre provisioning, carbon sequestration, nutrient retention, and support for biodiversity. With respect to climate change, wetlands may act as a carbon sink or source, depending on management conditions. Despite their value, wetlands are disappearing at an alarming rate, and threatened by hydrological alteration, pollution and climate change. For an effective wetland policy there is a need to relate the state of wetlands to regional and global land-use and climate change projections, and to relate ecosystem services to wetland processes. Wetlands are, however, generally under-represented in global models and assessments. Here we present a model that estimates vegetation biomass production, carbon emissions, and water quality of freshwater wetlands on a global scale with different hydrological and climate conditions. The main hydro-ecological processes are described in a generic way, accounting for climate zones, water level fluctuations and main hydrological types: rain-/groundwater fed (ponded) wetlands and surface water-fed floodplain wetlands (flooded). The model is coupled to global hydrological (PCR-GLOBWB) and climate and land-use (IMAGE-GNM) models. It estimates the wetlands ecosystem services, in particular regulating ecosystem services like water availability, carbon sequestration/emission and nutrient retention that are difficult to quantify otherwise. The model was applied to several wetland types in widely varying climate regions (Sweden, Germany, Spain, subtropical China, tropical Brazil and Kenya). Results show that the model generates plausible results compared to measured data of greenhouse gas emissions and nutrient concentrations. Furthermore, the model can discriminate between wetlands with different environmental conditions, resulting in wetlands being either a sink or a source of carbon. A regionalized parameterization is in progress. Further potential applications of model outcomes include regional assessments of wetland ecosystem services, determining ecosystem services under alternative management, climate and land use scenarios, and link these to conditions for biodiversity.