'Mass Die-Off': Thailand's Seagrass Crisis and the Island Fighting Back

We all know about the coral bleaching crisis, but not the seagrass tragedy. This is an ecosystem dying out entirely, and in heartbreaking silence. Seagrass is one of the three vital marine ecosystems alongside mangroves and coral reefs.

Seagrasses are the world's only higher plants that live entirely submerged, with approximately 60 species worldwide, and Thailand is home to 13 of them. These meadows shelter dugongs, grouper fry, blue swimming crabs, and tiger prawns. Professor Thon Thamrongnawasawat, Associate Dean of the Faculty of Fisheries at Kasetsart University says: "If our knowledge of corals is at 100%, our knowledge of seagrass is only at 5%. In just the past two years, 80–90% of seagrass has disappeared."

According to the International Union for Conservation of Nature (IUCN), seagrass absorbs 7–10 times more carbon than terrestrial forests and at least twice as much as mangroves. It is the world's most efficient carbon sink.  The problem is that marine heatwaves and extreme low tides are killing it at a rapid pace and restoration has felt almost impossible. Until now, on a far-away island in eastern Thailand.

To the people of Mak Island, known as Koh Mak, marine resources are their lifeline. Ung-Noppadol Sutthithanakul, Chairman of the Koh Mak Coral Conservation Group, has been diving these waters for decades, always passing through vibrant green seagrass meadows acting as a natural wave barrier and sanctuary for juvenile marine life. Then suddenly, the seagrass meadows started disappearing.

In the last 2–3 years, the water has heated up to more than 34°C. If you dip your leg in, you jump! The ideal temperature for seagrass is 29°C. The sun is intense, the low tides last longer. Sometimes the grass is exposed for half a day and scorches to death.

Professor Thamrongnawasawat added that research teams have measured seabed temperatures as high as 40°C. Seagrass stores energy in its roots, but the heat is now so extreme that the roots are rotting. "The Tape Seagrass (Enhalus acoroides) is the 'perennial tree' of the sea. It can live for 30-40 years. It is more like ginger," and it reveals a secret hidden beneath the seabed.

Thailand's largest seagrass species, the Tape Seagrass leaves can reach 2 metres while its underground rhizomes can also grow equally deep 2 metres, weaving together like a carpet. Its carbon-absorbing power is extraordinary: 10% is stored in the leaves which trap carbon-rich sediment, and 90% is locked in the underground roots for hundreds of years, quietly cycling carbon out of the atmosphere and into the earth.

For 15 years, Kasetsart University has searched for restoration methods that disturb wild plants as little as possible. Chatcharee Kaewsuralikhit, Head of the Seagrass for Climate Action Research Unit, explains: "Digging up rhizomes to replant works, but it destroys the existing source. We focused on growing from seeds and tissue culture."

One seed takes two years to become two plants - too slow. Tissue culture, a technique that grows a tiny piece of plant into a full new plant in a controlled environment, became a beacon of hope. After a decade of trial and error, the team has successfully stimulated one seed to produce 300 shoots. This is the first seagrass tissue culture lab in Thailand and in the world. The discovery has been patented to prevent commercial exploitation and ensure it serves nature. They began moving plants to sites where seagrass once thrived, such as Koh Mak.