The United Kingdom’s Blue Carbon Inventory: assessment of marine carbon storage and sequestration potential in Scotland (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 Scotland’s seas. It forms part of the UK’s Blue Carbon Inventory alongside regional reports that focus on the English North Sea (Burrows et al., 2021), the English Channel and Western Approaches Region (Burrows et al., 2024a) and the Irish Sea and Welsh Coast Region, the latter of which includes coastlines in Northern Ireland, England and Wales (Burrows et al., 2024b). The present report also draws on and updates information provided by the most recent Scottish blue carbon report (Cunningham and Hunt, 2023). As in the previous reports, the main objective was to assess the present extent and distribution of habitats, with emphasis on those that are identified as blue carbon habitats. Further aims were to evaluate the blue carbon potential of Scotland’s seas by (1) estimating the quantity of carbon currently stored within these various habitats, (2) establishing the average net sequestration rate (in g C/m²/yr), and (3) estimating the potential net total sequestration (in g C/yr) of each blue carbon habitat. 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 protect blue carbon ecosystems, the habitats they provide and their carbon sequestration potential. Evidence of this nature will contribute to exploration of the potential of the UK’s Marine Protected Area network to help mitigate against the effects of climate change. The extents of blue carbon habitats for Scotland’s seas were derived from available open sources, including the EUNIS level 3 combined map from the Joint Nature Conservation Committee (JNCC), individual habitat publications and datasets (Austin et al., 2021; Smeaton et al., 2022a,b), and recently published estimates of OC and IC stores in surface sediments (Smeaton et al., 2021).