May 6, 2025
- Seagrass meadows serve as powerful carbon sinks and key ecosystems for climate mitigation, fisheries and biodiversity but are under-researched and require increased investment.
- New Conservation International-backed research finds protecting vegetated coastal ecosystems could prevent over a billion tonnes of carbon pollution.
- Geography matters: Seagrass meadows in the Tropical Atlantic and Temperate Southern Africa have the highest carbon stocks.
Arlington VA (05/06/2025) — A groundbreaking global study published today reveals that protecting vegetated coastal ecosystems could avert climate damages valued at over $200 billion by preventing the release of 1.2 billion tonnes of carbon pollution – equivalent to removing the annual carbon footprint of 100 million U.S. homes.
Despite covering only 2% of the ocean floor, it’s known that vegetated coastal ecosystems – such as seagrass – store nearly half of the organic carbon buried in ocean sediments. Today’s new study, published in Nature Communications, is the most comprehensive review of vegetated coastal ecosystems to date, drawing from 3,240 seagrass and soil samples spanning 61countries. By examining more data points than ever, Conservation International, its International Blue Carbon Institute, and partner scientists discovered a far greater variation in seagrass carbon storage than previously recognized, revealing a much wider range of carbon storage in plants and sediments across species and regions.
"Seagrass ecosystems are the unsung heroes of climate change mitigation. Found on every continent except Antarctica, these crucial ecosystems are the critical foundation for coastal communities, yet significantly understudied and undervalued,” said Emily Pidgeon, a co-author of the study and Vice President for Ocean Science at Conservation International. “Genetically, seagrass beds are not very different from your lawn and are just as ubiquitous. This paper advances our understanding of seagrass's carbon sequestration potential, highlighting the need to include seagrasses as an element of a global solution to climate change and for further comprehensive research, particularly in the Global South.”
Key findings:
- Geographical Range: Seagrass meadows in the Tropical Atlantic and Temperate Southern Africa hold the highest carbon stocks, with medians of 40.6 and 96.2 metric tonnes per hectare – far exceeding the global median of 24.2 metric tonnes. In practical terms, a single hectare of seagrass in these regions can store the equivalent of 10 to 22 cars’ worth of annual emissions. Small delta regions along the coasts of South Africa, Spain, Italy, Greece, France, Colombia and Malaysia also showed above-average carbon storage, suggesting they may offer ideal conditions for seagrass carbon sequestration.
- Economic Impact: Seagrass is disappearing – if we don't protect seagrass, it could release 1.2 billion tonnes of CO2, costing the world more than $200 billion in damages.
- Updated Carbon Stock Estimate: Seagrass meadows store a global median of 24.2 metric tonnes of organic carbon per hectare within the top foot of seabed sediment. This is roughly equivalent to the annual carbon emissions of five gasoline-powered cars per hectare. The updated estimate is lower than previous calculations, providing a more accurate representation of seagrass carbon storage potential and its role in carbon credit valuation.
- Seagrass Diversity: Seagrass carbon storage varies by species. Some seagrass types store more carbon than others, especially those with strong roots. This means it's important to study which seagrass species are present when estimating carbon storage in a given meadow.
Lead author Dr. Johannes Krause, a Conservation International researcher and assistant research professor at Florida International University, said: “Seagrass meadows are not just important for marine biodiversity, they are a critical piece of the climate puzzle. This research underscores their vast potential as carbon sinks and the importance of accurate data to ensure we're protecting them properly. If we don't act now, we risk losing these ecosystems and the carbon stores they built up over centuries, compounding the effects of climate damage. It's time to prioritize seagrass conservation and research globally."
The study emphasizes that conserving existing seagrass meadows is among the most cost-effective strategies for mitigating climate change. Immediate actions are critical, including integrating seagrass protection into country commitments to the Paris Agreement (known as Nationally Determined Contributions) and expanding carbon credit methodologies to include seagrasses as a source of Blue Carbon.
Seagrass remains underrepresented in carbon financing initiatives compared to other vegetated coastal ecosystems like mangroves. Investing in global seagrass conservation can unlock the co-benefits of its carbon storage, fisheries support, coastal erosion protection and improved water quality, safeguarding our coastal ecosystems for the planet and humanity.
For more about Conservation International’s work on Blue Carbon and seagrass:
- In Colombia, a new way to protect mangroves takes root: Learn how Conservation International’s mangrove project is creating financial incentives to protect vital ecosystems and support coastal communities.
- International Blue Carbon Institute: Scaling global Blue Carbon action through innovative research, capacity-building and collaboration to maximize climate impact.
- Charting a Sustainable Future: Konservasi Indonesia's Strategic Partnership for Bintan Island's Marine Protected Areas
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About Conservation International: Conservation International protects nature for the benefit of humanity. Through science, policy, fieldwork and finance, we spotlight and secure the most important places in nature for the climate, for biodiversity and for people. With offices in 30 countries and projects in more than 100 countries, Conservation International partners with governments, companies, civil society, Indigenous peoples and local communities to help people and nature thrive together. Go to Conservation.org for more, and follow our work on Conservation News, Facebook, Twitter, TikTok, Instagram and YouTube.