Wetland Effects on Global Climate: Mechanisms, Impacts, and Management Recommendations

Wetlands are key locations in the landscape for the production, consumption, and exchange of greenhouse gases with the atmosphere. In this chapter, we review the major controls of wetland greenhouse gas fluxes and consider how wetlands influence global climate. It is a challenge to determine the overall climatic role of a wetland as the conclusion can vary depending on whether one wants to know the radiative balance over a defined period of time, the radiative forcing since 1750, or the lifetime climatic role of a wetland. For many wetlands, it is the long-term accumulation of soil carbon that eventually dominates the overall climatic impact of the wetland, such that wetlands that are hundreds to thousands of years old may have a lifetime cooling effect. Using a dynamic modeling approach, we consider how wetland disturbance, restoration, and mitigation affect wetland climate impacts. When a wetland is degraded, its functioning is reduced and greenhouse gas fluxes can change, thus altering the overall climatic role of the wetland. We demonstrate that disturbances to existing wetlands can cause warming that persists long after a wetland is restored or replaced by a mitigation wetland. Thus, activities that disturb wetlands and lead to the oxidation of sequestered soil carbon should be avoided to the maximum possible extent. Climate regulation is just one ecosystem service provided by wetlands; informed environmental management should consider the full range of wetland services and disservices when developing plans for wetland creation, restoration, and protection.