The carbon is stored below the canopy
A forest’s carbon total includes more than the wood and leaves visible above ground. In mangroves, a large share is held in the soil, where layers of roots, fallen material, and sediment can accumulate over long periods. This belowground store helps explain how mangroves can hold more carbon per area than many forests whose carbon is concentrated more heavily in living trees.
Tides help build the vault
Mangrove roots slow moving water and catch fine sediment carried in by tides. As new material settles, it can bury older organic matter beneath the surface. Flooding also limits how much oxygen reaches that buried material, so microbes generally break it down more slowly than they would in well-aerated soil. Some carbon therefore remains underground rather than cycling quickly back into the atmosphere as carbon dioxide.
The result is a layered record: newer roots and debris near the surface, with older carbon-bearing material buried below. The depth and amount of stored carbon vary with local conditions, including sediment supply, water movement, and how long the habitat has remained intact.
Disturbance can open the store
That buried carbon is not automatically permanent. If mangroves are cleared, drained, or otherwise disturbed, soils may be exposed to more oxygen or eroded away. Decomposition can then speed up, and some of the stored carbon can return to the atmosphere. Protecting a mangrove forest therefore preserves not only its trees, but also the slow-built soil beneath them—the part of the forest that may hold much of its carbon.
