Evaluating annual greenhouse gas budgets and climate change mitigation potentials of restored wetlands after a decade of flux measurements

Abstract:

Ecosystem restoration to mitigate climate change is increasingly being implemented as part of national and international climate mitigation strategies. Based on the principle that biomass production removes and sequesters atmospheric CO₂ in natural reservoirs, ecosystem restoration has the potential to counteract anthropogenic carbon emissions until more extensive decarbonization of our society is achieved and beyond that can continue to reduce atmospheric CO₂ concentrations in the long-term. Wetlands have the potential to sequester carbon with residence times on the order of 100-1000’s of years, as well as to provide additional valuable ecosystem services. One major impediment to wide-scale wetland restoration is understanding how to best manage ecosystems for their net climate benefits, including the emission of potent greenhouse gases such as methane. Emerging evidence shows that the net biogeochemical forcing of a wetland relies on a variety of factors including local site and soil conditions, ecosystem adaptations, disturbances and legacy effects, as well as past and future climate and land-use changes. Furthermore, there is much debate on what method is the most appropriate to account for the climate impact of short-lived climate pollutants with effects being asynchronous, non-linear, and timescale dependent.

Here we present more than 20 site-years of annual greenhouse gas budgets based on continuous CO₂ and methane flux measurements from several highly productive wetlands spanning different stages (5, 10, and 20 years) after restoration. We show that even with high methane emissions, some of the site-years were net greenhouse gas sinks soon after restoration and highlight the impacts of using different global warming potentials to account for methane emissions. We also investigated how site conditions affected GHG budgets between years and outline several issues that management and restoration strategies need to address to promote the overall climate change mitigation potential.