Mangrove Forests Among The Most Carbon-Rich In Tropics

Mangrove forests are among the most carbon-rich forests in the tropics, according to new research published in Nature Geoscience. The findings raise concerns about the magnitude of loss that the forests have endured and how this impacts the preservation of carbon resources, as well as carbon emissions.

Earlier research revealed that 30-50 percent of mangrove forests have been cleared in the last 50 years, and as much as 16 percent of the remaining mangroves are currently threatened. Now, new research reveals that mangroves are especially rich sources of carbon. Their deforestation could be responsible for 10 percent of greenhouse gas emissions, even though they make up just .7 percent of tropical forest area.

Scientists were already aware of the ecological importance of mangrove swamps, which support numerous ecosystems, encourage nutrient cycling, and offer fisheries. Many human communities subsist on the mangrove swamp ecosystem, and the trees serve to guard against the impact of tsunamis and typhoons.

Overharvesting, rising sea levels, and coastal overdevelopment have led to the mangrove forest decline, sparking concerns about the level of carbon emissions that may have resulted from their removal.

The research was a joint effort between the USDA Forest Service as well as the Center for International Forestry Research. The scientists were seeking to understand the impact of mangrove deforestation on the environment by measuring the amount of carbon stored in the forests. They measured the biomass within living and dead tree wood as well as soil carbon across 25 different mangrove forests in the Indo-Pacific region. The region encompasses the greatest variety and area of mangrove forests available for study.

Mangrove forests studied contained an average of 1,023 Mg of carbon per hectare, as much as four times as much carbon as other types of tropical forest, making them some of the richest-carbon forests in the tropics.

The mangrove trees are adept in their ability to store carbon because they use their roots to slow down tidal water and store sediment within a swampy ecosystem. A very carbon-rich environment results from low oxygen levels and slow decomposition.

Scientists are only beginning to understand the true extent of mangrove decline. In early 2010, the first global assessment of mangroves was conducted, which concluded that 11 of its 70 species face the threat of extinction, with declines greatest along the Central American coasts.

“The potential loss of these species is a symptom of widespread destruction and exploitation of mangrove forests,” said Beth Polidoro, principal author of the 2010 study. “Mangroves form one of the most important tropical habitats that support many species, and their loss can affect marine and terrestrial biodiversity much more widely.”

Late last year, satellite imagery released by the USGS and NASA revealed that there were 12.3 percent less mangroves than previously estimated. The research determined that there remains about 53,190 square miles of the forest.

The impact on humans can be extremely heavy as well, since the forests server as protection from natural disasters. Back in 2008, a cyclone hit Burma, killing vastly more people than was expected and causing many leaders to blame the tragedy’s impact on mangrove deforestation.  

“Encroachment into mangrove forests, which used to serve as a buffer between the rising tide, between big waves and storms and residential areas; all those lands have been destroyed,” said  Secretary-General Surin Pitsuwan  of the Association of South-East Asian Nations (ASEAN). “Human beings are now direct victims of such natural forces,” he continued, as quoted by the BBC.

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