Seagrass does not photograph well. There is no fluorescence, no colour cascade, no jaw-drop moment when you first see it. It is green blades moving in a current, and from a diver’s perspective it tends to look like something you pass over on the way to the reef. I have done exactly that, hundreds of times.
It is also, per square metre, one of the most ecologically productive ecosystems on the planet. And it is disappearing at a rate that should make headlines every week.
What Seagrass Actually Does
Seagrass meadows cover an estimated 300,000 square kilometres of shallow coastal seafloor worldwide. That is less than 0.2% of the ocean’s surface area, but these meadows are responsible for approximately 10% of the ocean’s total carbon burial. Seagrass sequesters carbon up to 35 times faster than tropical rainforest per unit area, storing it in root systems and sediment layers that can remain stable for thousands of years.
This makes seagrass a blue carbon ecosystem, alongside mangroves and saltmarshes, and one of the most cost-effective natural climate solutions known. When seagrass is destroyed, that stored carbon is released. A degraded seagrass meadow does not just stop absorbing carbon; it begins emitting it.
The ecological function extends well beyond carbon. Seagrass beds are nursery grounds for the juvenile stages of a remarkable proportion of commercial and reef fish species. In the Caribbean, an estimated 70% of commercially important fish species spend part of their life cycle in seagrass. In the Indo-Pacific, the figure is similar. The reef fish people travel across the world to dive with, snapper, grouper, parrotfish, barracuda, many of them grew up in seagrass. The coral reefs they ultimately inhabit are facing their own crisis from warming and bleaching.
Dugongs and green sea turtles are obligate grazers. They eat seagrass and only seagrass. Their populations are inextricably tied to seagrass health. When I see a green turtle on a reef, it has almost certainly come from a seagrass meadow nearby. The two ecosystems are not separate. They are connected.
The Scale of Loss
Since the 1930s, the world has lost an estimated 50% of its seagrass coverage. The rate of loss accelerated through the second half of the twentieth century: one analysis found that 7% of seagrass coverage was being lost every year between the 1990s and 2010s. That rate has not significantly slowed.
The causes are multiple and often interconnected. Coastal development destroys seagrass directly through dredging and land reclamation. Nutrient runoff from agriculture causes algal blooms that shade the seafloor and prevent the light photosynthesis that seagrass requires. Boat propellers scar meadows in shallow water. Climate change is warming and acidifying coastal waters outside the tolerance range of many species. Sedimentation from deforested coastal land smothers seagrass beds and blocks light.
In the Caribbean, the 2011 outbreak of stony coral tissue loss disease and the earlier devastation of long-spined sea urchin populations had cascading effects on seagrass through shifts in herbivory and nutrient cycling. Seagrass loss in one area accelerates degradation in adjacent reef habitat. The systems are too interlinked to treat as separate problems.
The Science Trying to Reverse It
Seagrass restoration is technically possible but logistically demanding. Unlike coral gardening, where fragments can be grown in nurseries and outplanted at depth, seagrass requires extensive shallow-water habitat with specific light, sediment, and salinity conditions. Labour costs are high relative to the area that can be restored in a given season.
The most successful restoration programmes work at scale with community involvement. Project Seagrass, a UK-based conservation charity, has been running restoration trials in the Solent and in Welsh coastal waters. Their work involves collecting seagrass seed from healthy meadows, placing seeds in biodegradable hessian bags, and deploying them by hand in restoration plots. The survival rates are modest, around 30 to 40%, but improving with each iteration.
In Florida, the restoration of Indian River Lagoon seagrass, severely damaged by nutrient pollution and algal blooms, has involved water quality intervention as much as replanting. You cannot restore seagrass in water that will immediately kill it. The upstream problem, nutrient loading from agriculture and urban runoff, has to be addressed first.
In Southeast Asia, community-led restoration in the Philippines and Indonesia has shown that local fishing communities, when engaged as partners rather than regulated as threats, are highly effective monitors and restorers of seagrass habitat. The knowledge held by fishing families about where seagrass was, what grew in it, and what has changed is irreplaceable.
What Divers Are Missing
Most dive briefings in seagrass areas focus on the adjacent reef. The meadow between the shore and the coral is where the boat anchors, where you fin through quickly to get to the good stuff. I have been guilty of this framing myself.
Seagrass diving is genuinely interesting if you slow down enough to look. Pygmy seahorses, pipefish, flounder, juvenile lionfish before their fins fully develop, blue-spotted stingrays resting in the sand at the meadow edge. Ghost pipefish, which are extraordinarily well camouflaged and use seagrass blades as shelter, are among the most sought-after macro finds in the Indo-Pacific. They live in seagrass.
The most practical thing a diver can do for seagrass is refuse to anchor in it. Anchor elsewhere, or use a buoy. Report degraded meadows through the Seagrass Spotter app, which feeds into a global mapping database. Choose boat operators who use mooring systems and brief guests on seagrass value rather than treating it as an obstacle to the reef.
The carbon stored in one square metre of intact seagrass meadow has been there, in some cases, longer than recorded history. It will take decades to restore once lost. Slowing the loss, right now, is orders of magnitude cheaper and more effective than any restoration programme. The same logic applies to marine protected areas: prevention is the most efficient form of conservation.
It does not photograph well. Do it anyway.
