The Science

Earth system models (ESMs) are essential tools to understand climate change impacts on wetlands. However, current ESMs usually represent wetland hydrology in oversimplified ways, resulting in low confidence of their projection of wetland evolution. In this study, researchers from Pacific Northwest National Laboratory (PNNL), Lawrence Berkeley National Laboratory, and the University of Michigan focused on improving the simulation of inundated wetlands in a fully coupled ESM by improving the infiltration scheme and calibrating parameter. The refined model simulates the wetlands and validates against satellite observations. With the refined model, researchers further found the wetlands over North America will be significantly affected by climate change under future scenarios.

The Impact

Climate change is threatening wetlands, but their vulnerability is far from well understood. Global warming has the capacity to profoundly affect hydroclimate components, and the net outcome of their interplay is complex. Before this study, scientists, engineers, and stakeholders had no predictive capacity to adequately project wetlands’ future fate. In this study, researchers used a state-of-the-science ESM that includes physical mechanisms of inundation and a range of climate scenarios to project changes and predict factors that can control wetland dynamics.

Summary

Climate change can alter wetland extent and function, and such impacts are perplexing. The study reveals projected changes in wetland characteristics over North America from 25° to 53° North under two climate scenarios using a state-of-the-science ESM. At the continental scale, annual wetland area decreases by ~10% (6–14%) under the high emission scenario, but spatiotemporal changes vary, reaching up to ±50 percent. As the dominant driver of these changes shifts from precipitation to temperature in the higher emission scenario, wetlands undergo substantial drying during the summer season when biotic processes peak. The projected disruptions to wetland seasonality cycles imply further impacts on biodiversity in major wetland habitats of the upper Mississippi, Southeast Canada, and the Everglades. Furthermore, wetlands are projected to significantly shrink in cold regions due to increased infiltration as warmer temperatures reduce soil ice. The large dependence of the projections on climate change scenarios underscores the importance of emission mitigation to sustaining wetland ecosystems in the future.

Contact

Funding

• This work was supported by the Earth System Model Development and Regional and Global Modeling Analysis program area of the U.S. Department of Energy, Office of Science, Biological and Environmental Research program as part of the multi-program, collaborative integrated Coastal Modeling (ICoM) project and Energy Exascale Earth System Model project.