Inundation of freshwater peatlands by sea level rise: Uncertainty and potential carbon cycle feedbacks

Freshwater peatlands represent an important component of global biogeochemistry through their role in carbon sequestration. Threats to carbon storage in freshwater peat include climate‐related increases in rates of oxidation and methanogenesis, increased wildfires, drainage, and dissolved organic carbon export from runoff. This paper discusses the potential impact of sea level rise on carbon fluxes from coastal peatlands, an issue not addressed by previous studies describing threats to peatlands from global climate change. We estimate carbon stocks and potential emissions from a coastal freshwater peatland located in North Carolina, United States. Four scenarios for inundation were modeled using Hadley‐CM3 scenarios (including the effects of collapsed barrier islands) with a lidar‐derived digital elevation model. Monte Carlo analysis was used to address model uncertainty and sensitivity of carbon emission parameters for three scenarios. Total existing carbon storage (peat and vegetation) on the Peninsula (5671 km 2 ) was estimated to range between 155.5 and 201.0 TgC (95% confidence intervals). Sea level projections ranged from 0.35 to 1.38 m by the end of the century and were estimated to inundate between 1260 and 3020 km 2 of the Peninsula. Carbon emissions from inundation of peat and vegetation ranged from 4.7–20.9 TgC (assuming inundation preserved peat deposits) to 99.4–128.0 TgC (assuming 100% emissions of inundated peat). While considerable uncertainty exists regarding the fate of carbon fluxes, we identify 150,000 km 2 of freshwater peatlands worldwide below 5‐m elevation and vulnerable to sea level rise. Our study suggests that future sea level rise may contribute a positive feedback to the global carbon cycle.