USDA Forest Service Pacific Southwest Research Station
CALIFORNIA – ALBANY-ARCATA-DAVIS-FRESNO-PLACERVILLE-REDDING-RIVERSIDE – HAWAII-HILO
SCIENCE THAT MAKES A DIFFERENCE
www.fs.fed.us/psw/
For Immediate Release: April 4, 2011
Contact: Sherri Eng, PSW Research Station Public Affairs, sleng@fs.fed.us; (510) 559-6327
Mangroves Among the Most Carbon-Rich Forests in the Tropics
Coastal trees key to lowering greenhouse gases
HILO, Hawaii— 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. (www.nature.com/naturegeoscience.com)
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.
This high-carbon storage suggests mangroves may play an important role in climate change management.
Aside from the main greenhouse gas contributor of fossil-fuel burning, the forestry sector can play a
part—especially carbon-rich forests that are being cleared rapidly on a global scale, such as mangroves.
―When we did the math, we were surprised to see just how much carbon is likely being released from
mangrove clearing,‖ says Donato. This suggests, says Donato, that where consistent with local
management objectives, mangroves may be strong candidates for programs aiming to mitigate climate
change by reducing deforestation rates.
Recently, mangroves have experienced rapid deforestation worldwide—a 30–50 percent decline in the
past 50 years. Mangrove deforestation generates greenhouse gas emissions of 0.02–0.12 petagrams of
carbon per year, which is equivalent to up to 10 percent of carbon emissions from global deforestation,
according to the research team’s findings.
The Pacific Southwest Research is headquartered in Albany, Calif. The station develops and
communicates science needed to sustain forest ecosystems and other benefits to society. It has
laboratories and research centers in California, Hawaii and the United States-affiliated Pacific Islands. For
more information, visit www.fs.fed.us/psw/.
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