Assessing, protecting and restoring the natural carbon storage capacity of marine sediments – the need for enhanced transdisciplinary dialogue and cooperation

As global warming progresses, sedimentary carbon sinks are becoming increasingly important in climate change mitigation measures. Thus, there is a need for in-depth knowledge of both the dynamics and vulnerabilities of the sedimentary carbon sinks, as well as the legal and political options to protect and restore their natural carbon sequestration efficiency. Here, we report on the transdisciplinary research project APOC, which addressed the Anthropogenic impacts on the cycling of Particulate Organic Carbon in the North Sea. Important results of the project include the quantification of sedimentation rates in the accumulation areas of the German Bight and the Skagerrak, assessing the factors that enhance organic carbon burial/storage and the determination of the sources and reactivity of deposited carbon. As major anthropogenic disturbances, the effects of bottom trawling and wind farm construction on benthic carbon storage were investigated and assessed. Bottom trawling in particular was significantly decreasing the benthic carbon storage due to a multitude of coupled physical and ecological effects. However, at the environmental policy level, it became clear that sedimentary deposits are not sufficiently recognized and protected as valuable natural carbon sinks, although their storage capacity is believed to be much higher than that of blue carbon ecosystems at similar latitudes. While the project was staffed mainly with natural scientists, important expertise in environmental policies was provided by the marine conservation office of the BUND, one of the largest environmental NGOs in Germany. As a fully-fledged project partner, BUND made it possible to recognize the relevance of the various project focal points for the environmental policy arena throughout the entire project. In turn, the policy experts were able to distribute the latest scientific findings to the environmental policy committees. In effect, the transdisciplinary cooperation within the project not only produced valuable scientific results, but also numerous expert briefings on environmental policy at all levels, from local authorities to the EU Parliament, emphasizing the importance of protecting natural fine-grained sedimentary carbon sinks for climate change mitigation measures. Key to this outcome was the continuous exchange of scientific findings and practical environmental policy knowledge, which kept all participants focused on the societal relevant objectives that were originally pursued with the project funding. The results of the project APOC can contribute directly to the new EU Nature Restoration Law adopted in June 2024. To this end, measures to strengthen and protect ecosystems both on land and in national coastal waters are to be introduced on 20 % of land and marine areas across the EU, including restoration of at least 30 % of important habitat types in poor condition by 2030.