Quantifying the carbon benefits of ending bottom trawling: ARISING FROM E. Sala et al. Nature https://doi.org/10.1038/s41586-021-03371-z (2021)

Bottom trawling disrupts natural carbon flows in seabed ecosystems owing to sediment mixing, resuspension and changes in the biological community. Sala et al.1 suggest that seafloor disturbance by industrial trawlers and dredgers results in 0.58–1.47 petagrams (Pg) of aqueous CO2 release annually (equivalent to 0.16–0.4 Pg carbon (C) per year), owing to increased organic carbon (OC) mineralization, which occurs after trawling. We are concerned, however, that Sala et al.1 overestimate trawl-induced CO2 release, because their model uses a reactivity value (k, the first-order decay rate) estimated for highly reactive OC delivered recently to the sediment surface, and apply it to bulk sediment (typically composed of labile, recalcitrant and refractory C), which is known to have a much lower reactivity2. These assumptions result in an upward bias in the estimated CO2 release by several orders of magnitude, overestimating the impact of trawling on global OC mineralization rates.