June 15, 2023 — Remember the headlines that claimed bottom trawling released as much carbon as all of air travel? We thought those claims were probably bogus when first reported, but Hiddink et al. 2023, a response paper published May 2023, now makes those claims Officially Bogus.
The original headlines came from Sala et al. 2021, a paper published in Nature that garnered more media coverage than any marine science paper of the past decade. We’ve covered the science and follow-ups over the last few years, but here’s a quick summary:
Sala et al. 2021 advocated for increasing the number of marine protected areas (MPAs) that restrict fishing. The paper used three different models that claimed benefits from MPAs:
- Food security – MPAs would increase food availability via more abundant fisheries.
- Biodiversity – MPAs would enhance ocean biodiversity.
Carbon/climate change – claimed that bottom trawling released as much carbon as all air travel, thus selling MPAs as a climate change solution via carbon sequestration. The paper suggested selling carbon credits from MPAs to fund the creation of more MPAs.
These three claims have quickly fallen apart, however. The original food security model was retracted, and the modified one by Sala et al. 2021 had similar issues. A response published last year points out that the biodiversity and carbon claims were based on the assumption that fishing disappears rather than being displaced. And now, Hiddink et al. 2023 demonstrates that the carbon model overestimated carbon benefits by 2-3 orders of magnitude, i.e., 100-1000 times.
Hiddink et al. 2023 notes two main reasons why the model in Sala et al. 2021 misfired:
- The fundamental assumptions of the carbon cycle were incorrect.
- The validation of those assumptions was also incorrect.
Here, we explain the carbon cycle in ocean sediment and discuss the potential for bottom trawling to contribute to carbon emissions. We also break down the carbon model from Sala et al. 2021 and show why it was incorrect based on Hiddink et al. 2023’s analysis.