Seagrasses

Seagrasses are a unique group of marine angiosperms (flowering plants) that grow fully submerged in shallow coastal waters. Forming extensive meadows across tropical and temperate regions, these foundation species play a critical role in shaping coastal ecosystems by influencing their physical, chemical, and biological environments. Seagrass meadows are among the most productive habitats on Earth and serve as critical building blocks for international marine ecological networks. 

 

Ecological Function and Connectivity 

Seagrass meadows function as natural coastal infrastructure. Their dense leaf canopies slow water movement, trap suspended sediments and organic matter, and buffer wave energy, while their root and rhizome networks stabilize the seafloor against erosion. These habitats are closely connected to adjacent coral reefs, mangrove forests, and other coastal ecosystems,  facilitating the continuous exchange of nutrients, organic material, and marine organisms across the wider coastal landscape, and enhancing the ecological resilience of coastal ecosystems.  

 

Significance for Migratory Species 

The health and extent of seagrass meadows directly influence the distribution and survival of numerous migratory species protected under the Convention on Migratory Species (CMS). Most notably, seagrasses provide essential feeding grounds for the dugong (Dugong dugon) - an obligate marine herbivore that depends almost exclusively on seagrass for its nutritional needs. Because dugongs frequently cross national borders to access these feeding areas, any degradation or loss of seagrass meadows in one location can have wider regional impacts, affecting migratory connectivity, reproductive success, and the long-term viability of dugong populations across their wider geographical range.  

Beyond dugongs, seagrass ecosystems support a diverse assemblage of migratory marine fauna, including sea turtles, fishes, and invertebrates, providing essential foraging, refuge, and nursery habitat throughout different stages of their life cycles. 

 

Blue Carbon & Climate Mitigation 

Seagrass meadows are increasingly recognized for their importance in global climate change mitigation. While covering less than 0.2% of the global ocean floor, they account for an estimated 10% of the ocean's annual organic carbon burial. By capturing atmospheric carbon through photosynthesis and trapping external organic particles within their sediment layers, seagrasses capture carbon dioxide away from the atmosphere and ocean, while their sediments accumulate and store both seagrass-derived and externally sourced organic carbon. Because these sediments are anoxic (oxygen-depleted), carbon can remain stored for centuries to millennia, making seagrass ecosystems one of the world’s most effective natural carbon sinks. Protecting and restoring seagrass meadows therefore contributes not only to biodiversity conservation but also to national and global climate objectives. Key Ecosystem Services Provided by Seagrass Meadows  

 
 

Ecosystem Service 

Primary Mechanism 

Conservation Value 

Blue Carbon Sequestration 

Long-term storage of organic carbon anoxic sediments. 

Supports climate mitigation efforts and  Nationally Determined Contributions (NDCs) under the Paris Agreement. 

 

Coastal Protection  

Reduction of wave energy and stabilization of seabed sediments  

Helps protect coastal communities and infrastructure from erosion and storm impacts.  

Water Quality Enhancement 

Nutrient cycling, sediment trapping, and particulate filtration. 

Improves water clarity and supports healthy, balanced benthic ecosystems. 

Biodiversity Support 

Provision of feeding, nursery, and shelter habitats. 

Sustains marine biodiversity and migratory species populations. 

Fisheries Productivity 

Nursery grounds for commercially important fish and invertebrates. 

Supports food security and coastal livelihoods. 

 

 

International Recognition 

The ecological, climate, and socio-economic values outlined above are increasingly reflected in international policy. The United Nations Environment Programme (UNEP) report Out of the Blue: The Value of Seagrasses to the Environment and to People provides a comprehensive overview of current scientific knowledge on seagrass ecosystems. It highlights the urgent need to reverse global seagrass decline and sets out 13 priority actions to support their conservation and restoration. 

The report also underscores that protecting seagrasses can make a significant contribution to Sustainable Development Goal 14 (Life Below Water), and support the implementation of Target 3 of the Kunming–Montreal Global Biodiversity Framework, which commits to conserving at least 30% of the world's land, waters and seas by 2030. Seagrass conservation likewise advances broader commitments under the UN Decade of Ocean Science for Sustainable Development and the UN Decade on Ecosystem Restoration (2021–2030), reinforcing the role of these habitats as a nature-based solution for both people and the planet. 

In response to the continued decline of these ecosystems, the 2030 Seagrass Breakthrough was developed to protect and restore over 16 million hectares of seagrass worldwide. Announced at COP28 by the CMS Office – Abu Dhabi in collaboration with the UN High-Level Climate Champions, the initiative provides a global framework through which governments, organizations, and communities can act together at scale. 

 

Global Spatial Datasets 

To support effective conservation planning, monitoring, and research, a range of global spatial datasets and mapping resources are available:  

  • Seagrass-Watch: Access and download citizen-science based seagrass dataset that include seagrass extent, composition, density and epiphyte presence. 
  • Seagrass Spotter: A global, crowdsourced, citizen science database aggregating georeferenced point data, photographic evidence, and observations regarding both the presence and absence of seagrass meadows worldwide.