World Seagrass Day

Sri Lanka’s Global Leadership and the Urgent Call to Protect Our Underwater Forests

On 23 May 2022, the United Nations General Assembly adopted by consensus a resolution declaring 1 March as World Seagrass Day a landmark initiative spearheaded by Sri Lanka and co-sponsored by 24 other nations. With this historic step, Sri Lanka placed one of the world’s most overlooked marine ecosystems firmly on the global environmental agenda.

As we mark World Seagrass Day once again, the declaration is more than symbolic recognition. It is a reminder that beneath our coastal waters lies an ecosystem that sustains fisheries, protects shorelines, mitigates climate change and supports coastal livelihoods yet continues to decline at an alarming rate.

The Hidden Forests Beneath the Sea

Seagrasses are not seaweeds. They are true flowering plants angiosperms that evolved from terrestrial monocotyledonous plants between 70 and 100 million years ago. Over time, they developed extraordinary adaptations to survive completely submerged in marine and estuarine waters. They possess leaves, roots, rhizomes and even conduct submarine pollination. Internal gas transport systems and epidermal chloroplasts allow them to photosynthesise efficiently underwater, provided sufficient sunlight penetrates the water column.

Globally, seagrasses occur in 159 countries across six continents and cover an estimated 300,000 to 600,000 square kilometres of the ocean floor. Despite occupying just 0.1 percent of the seabed, they form some of the most productive marine ecosystems on Earth. Scientists currently recognise 72 species across six families and twelve genera worldwide.

Ecosystem Engineers and Fisheries Powerhouses

Seagrass meadows are often described as the “ecosystem engineers” of the sea. Like forests on land, they create complex habitats that shelter, feed and nurture marine life. Crustacean and fish abundances can be seven to twenty times higher in seagrass meadows compared to adjacent sandy areas. These underwater meadows serve as nursery grounds for over one-fifth of the world’s largest 25 fisheries, making them foundational to global food security.

More than one billion people live within 100 kilometres of a seagrass meadow. For many coastal communities, especially in developing nations, seagrass-associated fisheries provide subsistence, income and cultural continuity. Species such as sea turtles and dugongs rely directly on seagrass for food, while commercially important reef and mangrove fish depend on these habitats during their juvenile stages.

Research estimates that the ecosystem services provided by seagrasses are valued at approximately USD 34,000 per hectare annually. Their contribution extends beyond fisheries to nutrient cycling, sediment stabilisation, and maintaining water clarity which in turn benefits coral reefs and tourism.

The Ocean’s Carbon Vault and Coastal Shield

Seagrasses are among the most efficient natural carbon sinks on the planet. Collectively, they store an estimated 19.9 petagrams of organic carbon and may account for up to 18 percent of oceanic carbon storage. Carbon is locked within their extensive root and rhizome systems and buried in sediments for centuries.

In addition to mitigating climate change, seagrass meadows stabilise sediments, reduce coastal erosion and buffer wave energy during storms. In a climate-vulnerable island nation like Sri Lanka, these functions are critical. They serve as living infrastructure, protecting coastal communities from flooding and storm surges.

Seagrasses also regulate seawater chemistry by absorbing dissolved carbon dioxide, helping reduce ocean acidification. Studies have shown they can reduce harmful marine bacteria in surrounding waters, contributing to both coral reef health and safer seafood supplies.

Sri Lanka: A Seagrass Biodiversity Hotspot

Situated in the Indo-Pacific bioregion – one of the most diverse seagrass regions globally, Sri Lanka hosts 15 true seagrass species across seven genera. These meadows occur in shallow marine and estuarine waters, particularly in the Gulf of Mannar, Palk Bay, Jaffna Lagoon, Puttalam Lagoon, Negombo Estuary, Batticaloa Lagoon and coastal areas stretching from Kalpitiya to Mullaitivu.

Scientific documentation of Sri Lanka’s seagrasses dates back to the early 18th century, with herbarium records from Puttalam Lagoon in 1826. A comprehensive review in 1991 identified fifteen species, and subsequent updates incorporating genetic studies have refined the national checklist.

Despite their ecological significance, data gaps remain. Decades of civil conflict limited research in the North and East, where extensive meadows are believed to occur. Inconsistencies in historical mapping estimates ranging from approximately 200,000+ hectares to over 37,000 hectares highlight the urgent need for comprehensive national mapping and long-term monitoring.

Accelerating Decline: A Global and National Concern

Globally, nearly 30 percent of seagrass meadows have already been lost. Since the 1990s, annual loss rates have accelerated to approximately 7 percent per year. An estimated 110 square kilometres disappear annually – equivalent to two football fields every hour. Only 26 percent of known seagrass areas fall within Marine Protected Areas, making them the least protected major coastal ecosystem compared to coral reefs and mangroves.

Sri Lanka mirrors these challenges. The Negombo Estuary alone experienced a 96 percent decline between 1997 and 2004, largely due to nutrient loading and microalgal overgrowth. Destructive fishing practices such as drag nets, push nets and trawling have damaged seagrass beds in multiple lagoons. Additional threats include sedimentation from unplanned coastal development, pollution from river discharge, shrimp hatchery activities, anchoring damage, and climate-induced temperature rises.

Seagrasses have often been termed the “ugly duckling” of conservation –overshadowed by coral reefs and mangroves despite comparable or greater ecological value. Yet their continued degradation directly threatens fisheries, livelihoods and climate resilience.

From Awareness to Action: Sri Lanka’s Continued Commitment

Sri Lanka’s leadership in establishing World Seagrass Day reflects its broader commitment to marine conservation and sustainable development. The observance aligns with the 2030 Agenda for Sustainable Development, the Paris Climate Agreement and national climate commitments. Integrating seagrass conservation into Nationally Determined Contributions can strengthen both climate mitigation and adaptation strategies.

The Ministry of Environment, in collaboration with the Coastal Conservation and Coastal Resource Management Department, is engaging fishing communities directly. Awareness programmes, stewardship initiatives and youth engagement campaigns aim to bridge the gap between policy and practice.

Long-term solutions require systematic mapping, molecular research to clarify species identification, national monitoring networks, restoration trials and strengthened marine protection measures. Empowering local communities to lead monitoring and conservation efforts will be central to success.

A Future Anchored in Seagrass

Seagrasses are silent guardians of our seas. They sustain fisheries, absorb carbon, protect shorelines and support biodiversity – all while remaining largely invisible to the public eye.

World Seagrass Day is an invitation to change that.

Sri Lanka has taken global leadership in recognising these ecosystems. Now, the challenge is to transform awareness into restoration, policy into protection, and science into sustained stewardship.

A resilient ocean and a climate-secure future depend not only on coral reefs and mangroves, but also on the quiet underwater forests that bind marine ecosystems together.

On this World Seagrass Day, let us reaffirm our collective responsibility – as a nation and as a global community – to ensure that these vital meadows continue to thrive for generations to come.

Information and images courtesy of Susantha Udagedara, Director, Seagrass and Climate Change Programme at Blue Resources Trust (BRT)