Marine and coastal ecosystems are increasingly recognised as critical allies in addressing the climate crisis. While terrestrial nature-based solutions, such as forest and peatland restoration, have long dominated global climate strategies, the role of ‘blue carbon’ – particularly that stored and sequestered by coastal habitats – is only now beginning to receive the attention it deserves. Yet despite their potential, many of these habitats remain poorly understood and undervalued, especially within Europe.
The Endangered Landscapes & Seascapes Programme is working to boost restoration efforts across Europe and inform future planning. UNEP-WCMC has collaborated with the Programme on a scoping exercise to assess the climate change mitigation potential of marine and coastal ecosystems across the continent. This work examines the evidence for carbon storage and sequestration in these habitats and explores barriers to integrating them into wider biodiversity and restoration strategies.
Blue carbon restoration in action
Blue carbon refers to the carbon captured and stored by marine and coastal ecosystems. In Europe, these include seagrass meadows, tidal flats, kelp forests, mollusc reefs, and seabed sediments. However, knowledge of the role they play in the carbon cycle remains limited. While seagrass meadows and saltmarshes are officially recognised as blue carbon habitats, the carbon storage and sequestration potential of other habitat types is not well understood.
The new report investigates what is currently known about the contribution of these ecosystems to climate change mitigation and whether restoring them from a degraded state could help achieve both nature and climate goals.
The Endangered Landscapes & Seascapes Programme supports large-scale restoration projects that aim to recover biodiversity and ecological processes across Europe. Several of these projects are seascapes that include marine and coastal components, each embedded within unique ecological and socio-political contexts. They represent the diversity of Europe’s coasts, from the Amvrakikos Gulf in Greece, where murky waters conceal distinctive Rhodolith beds (formed by calcareous red algae), to the submerged Dogger Bank in the North Sea between the UK and mainland Europe, where industrial activity has degraded critical spawning sites for rays and sharks.
The current state of climate change mitigation assessment
As part of the scoping exercise, more than 50 peer-reviewed articles, technical reports, and project documents were reviewed to assess existing knowledge and data relevant to greenhouse gas dynamics in Europe’s marine and coastal habitats. The analysis focused on three key metrics: carbon storage, carbon sequestration, and greenhouse gas emissions (including methane and nitrous oxide).
The review found that traditional blue carbon ecosystems, particularly saltmarshes and seagrass meadows, are supported by a more comprehensive knowledge base, including established measurement and assessment methods. By contrast, other habitats – such as macroalgae, maerl beds, mollusc reefs, and undisturbed seabed sediments – remain comparatively underdeveloped in terms of available guidance. While these systems may have some climate mitigation potential, data availability and consistency remain major barriers.
Across all systems, a recurring limitation is the lack of data on methane and nitrous oxide emissions. These gases are essential for determining whether a habitat functions as a net sink or source under different conditions. Without accounting for them, assessments risk overlooking trade-offs or overestimating benefits.
The need for a holistic seascape approach
Habitats in coastal zones are tightly interlinked, including in their carbon dynamics. For example, seagrass meadows trap sediments that nourish adjacent saltmarshes, while mollusc reefs enhance water clarity, supporting seagrass growth. Assessing these ecosystems in isolation risks underestimating their combined mitigation potential and the resilience benefits they offer. A seascape approach could integrate these linkages, recognising that restoring one habitat type can amplify benefits in others. However, existing assessment methods do not yet quantify how connectivity within seascapes can enhance climate change mitigation outcomes.
Another key finding from the review is that while carbon sequestration is an important function, marine and coastal restoration must be understood in a wider context. Many interventions that enhance carbon sequestration and storage, such as restoring seagrass beds or reducing bottom trawling, also deliver biodiversity gains, support fish populations, and provide climate adaptation benefits like storm protection. Yet climate-focused methodological frameworks tend to concentrate narrowly on quantifying carbon benefits.
Policy recommendations
The review identifies several actions that could strengthen the evidence base and support integration of marine and coastal restoration into climate strategies:
- Improve the evidence base for coastal and marine ecosystem coverage, mapping extent and condition: without this information, further assessments of climate mitigation potential are impossible.
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- Harmonise monitoring indicators and protocols, ensuring compatibility with the Intergovernmental Panel on Climate Change (IPCC) and voluntary carbon market methodologies.
- Take a broader look at seascape restoration: scaling up would require understanding the benefits of connectivity across habitats, as well as trade-offs between climate mitigation and other co-benefits including supporting fisheries and storm protection.
Looking ahead
By synthesising the available evidence on blue carbon in European seascapes, this scoping work lays the foundation for future monitoring and investment in marine restoration. As restoration ambitions grow under the EU Biodiversity Strategy and the UN Decade on Ecosystem Restoration, building a clearer picture of the climate mitigation potential of these ecosystems – as well as the other benefits they provide for people and nature – will be vital for achieving integrated biodiversity and climate goals.
This article was written by Reka Marton, Nature-based Solutions Intern at UNEP-WCMC. To find out more, visit the Estimating Climate Benefits project page.
