The United Kingdom’s Blue Carbon Inventory: assessment of marine carbon storage and sequestration potential in UK seas (including within Marine Protected Areas)

This report was commissioned by WWF, The Wildlife Trusts and the RSPB to assess the extent, scale, distribution and potential of the current blue carbon sinks in the region of water in the UK’s Exclusive Economic Zone (EEZ), the UK continental shelf (including Rockall) and the Territorial Seas of the Isle of Man (‘UK seas’). This report summarises the four regional reports of the UK’s Blue Carbon Assessment: (1) the English North Sea Region (Burrows et al., 2021), (2) the English Channel and Western Approaches Region (Burrows et al., 2024a), (3) the Irish Sea and Welsh Coast Region, which includes coastlines in Northern Ireland, England and Wales (Burrows et al., 2024b) and (4) the Scotland Region (Burrows et al., 2024c). The objectives of this synthesis report were to summarise the series of reports in order to provide (1) information on the current extent and distribution of blue carbon habitats, including seabed sediments and coastal vegetated habitats, (2) estimates of the quantity of carbon currently stored across the four assessment regions, (3) assessments of the average net sequestration rate (g C/m²/yr), and (4) the potential net total sequestration (g to Mt C/yr) of blue carbon habitats and their contribution to differences among regions and their areas designated for protection. This report also aims to compare the similarities and differences between regions, including the quantity of blue carbon within existing marine protected areas. The focus of this series of reports has been on stores and accumulations of organic carbon (OC) as particulate material rather than inorganic carbon (IC), given the likely net production of CO₂ through the production of IC as shell material. Carbon store densities and rates of production and storage have been combined with measures of habitat area to give estimates of total carbon stored in blue carbon habitats and their associated sediment stores. The results are intended to inform management decisions and identify opportunities to enhance the seabed and its carbon sequestration potential. This evidence will contribute to exploration of the potential of the UK Marine Protected Area (MPA) network to help mitigate against the effects of climate change. The extents of blue carbon habitats for UK seas were derived from available sources, including the EUNIS level 3 combined map from the Joint Nature Conservation Committee (JNCC), Natural England Marine Habitats and Species Open Data, and recently published estimates of OC and IC in long-term stores in surface sediments (Smeaton et al., 2021a).