Mangrove in Australia, photo: Richard Taylor/Creative Commons.
We've known that the world's mangroves are in decline, with 30-50% of them being cleared in the past half century and 16% of them currently threatened. Now new research shows that mangroves are the most carbon-rich forests in the tropics, clearing them being responsible for about 10% of greenhouse gas emissions from global deforestation despite being just 0.7% of tropical forest area. Based on work done by scientists from the Center for International Forestry Research and the USDA Forest Service, published in Nature GeoScience, mangrove forests in the Indo-Pacific region stored up to four times as much carbon as other types of tropical forest.
Mangrove forest on the Pacific coast of Costa Rica, photo: Mat McDermott.
Why do mangroves store so much carbon? In part they store so much carbon because of the tangled root systems typical of the trees there. Those roots slow down tidal water and allows more sediment to settle, which combine with low oxygen levels there slowing the rate of decomposition, to create an incredibly carbon-rich environment. On average, the soil in mangrove forests store five times more carbon that soil in other types of forest. In fact mangroves store more carbon just in the soil than do most tropical forests in soil and above ground biomass.
Current threats to mangrove forests from rising sea levels (to which mangroves have been able to adapt in the past, moving inland), from clearance by urban and industrial development, and from fish farms, is such that there is a risk that within the next century mangrove forests may disappear entirely.
Fishing in the Sundarbans, the vast forest in India and Bangladesh that forms part of the delta of the Ganges and Brahmaputra rivers. Photo: Frances Voon/Creative Commons.
Beyond the importance of mangroves in storing carbon, they provide very important barriers in storms, reducing the impact of typhoons and tsunamis. They also are important sources of food for people living near them and habitat for myriad animals.
Here's the original research: Mangroves among the most carbon-rich forests in the tropics
More on Mangroves:
Earth Has 12% Fewer Mangroves Than Previously Thought, New Satellite Data Reveals Sixteen Percent of the World's Mangrove Forests Threatened With Extinction