Restoring riparian wetlands for carbon and nitrogen benefits and other critical ecosystem functions.

With global warming intensifying, freshwater wetland restoration is becoming an increasingly important natural climate solution. Yet, restoration efforts for climate benefits have mostly focused on peatlands due to their high carbon storage capacities. Nevertheless, restoration often results in substantial methane emissions, complicating the climate benefits of restoration. Contrastingly, the climate benefits of restoring non-peat wetlands remain largely unexplored. We investigated the short- and long-term effects of restoring riparian wetlands to reinstate critical carbon dynamics and other ecosystem functions. Using a paired experimental design, we monitored carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) fluxes before, during, and after restoration. We also monitored native wetland plant cover, surface organic carbon and nitrogen stocks, leaf litter input, organic matter decomposition, and soil moisture. In the short term (one year post-restoration), rewetting and active revegetation reduced net carbon emissions by 39 % and increased surface organic carbon and nitrogen stocks by 12 % and 43 %, respectively. Restored wetlands had higher native plant covers, with native litter experiencing less decomposition than invasive litter, likely promoting carbon preservation. Furthermore, restored wetlands retained 55 % more soil moisture after drying, with moisture levels increasing with increasing soil carbon contents. Together, these results indicate the reinstatement of critical functions like reduced carbon mineralisation, and increased nutrient retention and soil water storage. In the longer term (six years post-restoration), surface organic carbon stocks increased by 53 %, demonstrating sustained long-term benefits. Our study highlights the effectiveness of riparian wetland restoration as a natural climate solution, providing critical insights for restoration policies beyond peatlands.