An opinion on BlueCAM an Australian blue carbon method to estimate climate change mitigation benefits of coastal wetland restoration by Lovelock et al. (2022)

BlueCAM is an Australian coastal wetland restoration methodology for estimating atmospheric warming abatement. However, BlueCAM is incomplete and contains conceptual and formulation errors. Conceptually, sequestration may be understated by not accounting for an increase in animal biomass and baseline ecosystems as heterotrophic carbon sources. Or, more likely, sequestration services are significantly overestimated by not considering: (1) remineralization of allochthonous carbon, supplied from surrounding ecosystems; (2) the subtraction of a notable intrinsically recalcitrant allochthonous carbon fraction; (3) whether baseline ecosystems are autotrophic carbon sinks; and (4) the reduction in air-sea flux during periods of submersion. Erroneously, BlueCAM: (1) implies that any remains of labile allochthonous carbon should be subtracted from stocks, not just the recalcitrant fraction; and (2) does not embed additional warming from CH4 emissions within components of net ecosystem production. Taken together, these errors are likely to greatly overestimate both wetland sequestration and warming abatement services.