Mangroves Among the Most Carbon-Rich Forests in the Tropics; Coastal Trees Key to Lowering Greenhouse Gases

Coastal mangrove forests store more carbon than almost any other forest on Earth, according to a study conducted by a team of U.S. Forest Service and university scientists.

Their findings are published online in the journal Nature Geoscience.

A research team from the U.S. Forest Service's Pacific Southwest and Northern research stations, University of Helsinki and the Center for International Forestry Research examined the carbon content of 25 mangrove forests across the Indo-Pacific region and found that per hectare mangrove forests store up to four times more carbon than most other tropical forests around the world.

"Mangroves have long been known as extremely productive ecosystems that cycle carbon quickly, but until now there had been no estimate of how much carbon resides in these systems. That's essential information because when land-use change occurs, much of that standing carbon stock can be released to the atmosphere," says Daniel Donato, a postdoctoral research ecologist at the Pacific Southwest Research Station in Hilo, Hawaii.

The mangrove forest's ability to store such large amounts of carbon can be attributed, in part, to the deep organic-rich soils in which it thrives. Mangrove-sediment carbon stores were on average five times larger than those typically observed in temperate, boreal and tropical terrestrial forests, on a per-unit-area basis. The mangrove forest's complex root systems, which anchor the plants into underwater sediment, slow down incoming tidal waters allowing organic and inorganic material to settle into the sediment surface. Low oxygen conditions slow decay rates, resulting in much of the carbon accumulating in the soil. In fact, mangroves have more carbon in their soil alone than most tropical forests have in all their biomass and soil combined.