Carbon neutrality does not equal climate neutrality in saltmarsh restoration

Abstract

Abstract Saltmarsh restoration efforts often highlight high carbon burial rates as a climate mitigation opportunity. We created a 200-year managed-realignment model incorporating carbon burial, albedo change, and emissions of climate-active compounds across three successive realignment stages: mudflat, realigned saltmarsh, and mature saltmarsh. Total climatic outcomes from all forcing agents differ substantially from those derived solely from carbon burial across latitude and over time. Latitude explains a significant proportion of variation in emissions for methane, methyl bromide, and methyl chloride in mature saltmarshes and carbon burial in mature and realigned saltmarshes. The climate mitigation effects of managed realignments were significantly reduced at subtropical latitudes, and aerosol and albedo impacts had greater influence on total radiative forcing relative to carbon burial. Future land-use mitigation strategies should therefore use spatiotemporally explicit accounting of climate-impacting processes and not rely solely on carbon budgets to underpin climate mitigation strategies.