Seagrass: Definition

Updated 2026-11-02 · 1 min read · By the akar.earth specialist team

What is seagrass? How seagrass meadows store blue carbon in sediments, why seagrass credits are still rare, and what Indonesia's meadows mean.

Seagrass is a group of flowering plants that grow fully submerged in shallow coastal waters, forming underwater meadows. Seagrass meadows are a blue carbon ecosystem: they trap sediment and organic matter, and store carbon in the seabed beneath them.

Why it matters

Seagrass meadows support fisheries, feed dugongs and turtles, stabilise sediments and filter water. Their sediments can hold substantial carbon, accumulated slowly over time. When meadows are lost to dredging, pollution, boat damage or coastal development, sediments can erode and release carbon. Protecting and restoring them supports both climate and coastal livelihoods.

How seagrass carbon is measured

• Sediment cores: carbon content and bulk density to a defined depth.
• Source of carbon: part of the sediment carbon comes from outside the meadow (for example from land or mangroves), which methodologies may handle differently.
• Extent mapping: drones, snorkel or dive surveys and satellite imagery in clear water.
• Above-ground biomass: small and seasonal, so usually a minor pool.

Seagrass restoration falls within Verra’s VM0033. Measurement is harder than for mangroves, because sediment accumulation is slow and variable and meadows shift naturally. See our seagrass carbon guide.

Indonesia angle

Indonesia has extensive seagrass meadows across its archipelago, including around Sulawesi, Maluku, Nusa Tenggara, Bali and Papua, and is a centre of seagrass species diversity. Meadows face threats from coastal development, sedimentation, seaweed farming and destructive fishing. Seagrass is known locally as lamun, and meadows as padang lamun. Coastal and marine management involves marine affairs authorities and local communities, so tenure and governance need early clarification for any carbon project.

Common mistakes

• Assuming high carbon stocks from global averages instead of measuring locally.
• Ignoring carbon imported from outside the meadow.
• Treating natural seasonal dieback as permanent loss, or the reverse.
• Overlooking fisher and community use of meadows.

Related terms

See blue carbon, mangrove and WRC, or explore the blue carbon hub.