A Critical Analysis of Blue Carbon Storage and Wetland Offset Credits

Abstract:

Coastal wetlands store a significant amount of terrestrial soil carbon known as “blue carbon.” Tidal marsh sediment core analyses as well as depth probe measurements conducted by this research team indicate that blue carbon stocks are routinely underestimated. Globally, tidal marshes are being lost at a rate of 1-2% per year due to conversion and degradation (Pendleton et al., 2012), and sea level rise will contribute to additional loss. As coastal wetlands are degraded or destroyed, a variable portion of stored blue carbon is disturbed, remineralized, and emitted to the atmosphere in the form of carbon dioxide, a potent greenhouse gas. Our data suggests that human development has negatively impacted wetland health and subsequently decreased blue carbon storage. The efficacy of coastal ecosystems at storing carbon is the basis for their inclusion in global carbon offset schemes, but that approach may be misguided. This paper critically analyzes the role of coastal wetlands in carbon budgets, and challenges the notion that these ecosystems can effectively counterbalance anthropogenic emissions due to projected loss and declines in wetland health. Three tidal marshes in the Hudson Estuary are examined, and historic as well as future blue carbon stock loss is estimated. We propose that the conservation of these ecosystems be treated as a mitigation strategy rather than as the basis for offset credits. Alternative financial incentives for wetland protection are considered, as well as the intrinsic valuation of these ecosystems and ramifications for environmental justice zones.