What’s happening? The UK is set to become the first country to create a complete map of its stores of blue carbon through an initiative led by the Scottish Association for Marine Science and funded by WWF-UK. The project will build upon blue carbon mapping which started in Scotland to cover the Irish Sea and English Channel. Initial findings will be released later this year, with a final report set to follow in summer 2023. Mapping the country’s blue carbon habitats will allow governments to plan and prioritise the use of marine environments. (The Independent)
Why does this matter? Even though over two-thirds of the UK is underwater when its continental shelf is considered, knowledge around its blue carbon sequestration capacity (along with that in other countries) is still limited, with most carbon accounting previously targeting terrestrial habitats. Understanding the distribution and extent of blue carbon stores will provide knowledge that can support conservation measures and climate resilience. It could more broadly support the UK’s progress toward achieving its net-zero targets. A diverse range of marine habitats can be found in the UK’s seas including seagrass beds, kelp forests, saltmarsh, biogenic reefs and marine sediments. An initial pilot study of the North Sea last year by WWF estimated the superficial top 10 cm of English North Sea seabed sediments store 100.4 million mt of CO2, the equivalent of around 20% of the stocks sequestered in UK forests and woodlands. However, since seabed sediments can be hundreds of metres in depth, the 10 cm figure should be viewed as a significant underestimate of the total organic carbon sequestered in the seabed. Another key finding of the pilot study is that 98% of total organic carbon is stored in sand and mud, among other seabed sediments, making these the most important areas for blue carbon sequestration in the region. Given there is no sufficient restoration solution for these sediments, preservation efforts and managing activities to minimise disruption to them are key. This is important as areas with the highest carbon stock density, including the Devil’s Hole region toward the north of the study area, lie outside marine protection area (MPA) designation. The researchers estimated 1.2 million mt of organic CO2 is added each year to ocean sediments, but it is still unknown how much of this is sequestered in the long-term due to multiple disturbances to the seabed. Physical disturbances caused by fishing practices, offshore energy infrastructure installations, aggregate dredging and other activities are the main pressures faced by organic carbon stores across nearly all English MPAs. The UK has lost over 90% of its carbon-storing seagrass over the last two centuries, with nearly 50% of the losses predicted to have occurred in the last 30 years. A separate study exploring the climate impacts of global bottom trawling found trawling alone causes around one billion mt of CO2 every year to be released from the seabed – the equivalent of the total emissions produced by the aviation industry annually. Additionally, there are other benefits to stopping such disruptive ocean practices. Implementing protection measures to target 45% of the ocean has potential to preserve 70% of all biodiversity. Banning fishing from certain areas could also boost global fish yields by up to eight million mt. Climate change impacts such as ocean acidification result in mixed effects on blue carbon capture and sequestration. While photosynthetic organisms such as macroalgae or kelp could potentially benefit from higher CO2 concentrations, other marine species and habitats such as carbonate sediments and carbonaceous organisms including coral and molluscs will be negatively impacted as they find it more difficult to grow shells and exoskeletons. Findings from the blue carbon mapping study will provide important baseline knowledge to support policymaking and build a case for identifying and stewarding blue carbon-rich habitats in the ocean. Other independent efforts to calculate the carbon stored in the world’s seabeds are underway, such as the five-year research partnership between the Blue Marine Foundation and insurer Convex Group to establish an open-access database for global blue carbon storage.