Losing Carbon: Man Oh Man, Those Mangroves

by Bill Chameides | April 7th, 2011
posted by Erica Rowell (Editor)

Permalink | Comments Off on Losing Carbon: Man Oh Man, Those Mangroves

Mangroves are lots of things, including prime habitat and breeding grounds for all sorts of critters, like the white heron. (U. S. Geological Survey / South Florida Information Access [SOFIA])

Mangroves pack a mighty carbon punch.

Yesterday the topic was the larch of Siberia’s boreal forests. Today we find ourselves in the forest again, but considerably south of yesterday’s environs — in the mangrove stands of the tropics and subtropics.

How Mangroves Stand Out

Mangrove forests are definitely cool, in the colloquial sense of the word.

Highly specialized to their particular environment, the intertidal zone along coasts and in estuaries, they must be able to withstand the ocean’s ebb and flow, and with them, large fluctuations in levels of standing water, salinity, and oxygen in soil, which tends to be low.

Oh, and for ultra cool: Mangrove forests typically have their tangle of roots above ground; these so-called stilt roots are specially adapted to absorb oxygen from the air. (See pictures above and below.)

Mangroves are coastline-hugging trees that provide myriad benefits. But they are disappearing and the loss is being exponentially felt. (Caroline S. Rogers/USGS)

Mangroves As Important Storm Buffers

Mangroves made headlines [pdf] following the devastating Asian tsunami of 2004 when hundreds of thousands of people [pdf] across Indonesia, Sri Lanka, India, Thailand, and the Maldives died.

But some areas experienced more deaths than others, such as two nearby villages where one experienced two fatalities and the other up to 6,000.

Why? Studies (such as this one and this one) suggest that the presence of mangrove forests played a role, providing a buffer against powerfully surging ocean water.

In a similar vein, this study by Saudamini Das of the University of Delhi, India, and the Nicholas School’s Jeff Vincent indicates that coastal communities with mangroves generally do better against storms and surges than communities without them.

Some of the Many Other Benefits Mangroves Provide

Protection isn’t the only reason to value mangroves. These coastal forests provide a whole bunch of services, like spawning grounds for fisheries (one estimate links mangroves to 80 percent of the global daily catch), land stabilization and sediment control, and wood products, to name but a few.

A new paper by Daniel Donato of the USDA Forest Service and colleagues, published in the journal Nature Geoscience, documents another benefit of mangrove forests: a huge reservoir of tons and tons of carbon. Unfortunately, as the authors report, mangrove forests are disappearing at a hefty rate.

Here is the story by the numbers. (Note: where not explicitly stated, the source is the Donato paper.)

Carbon Stored per Acre by Forest Type

Forest Type Approximate Amount of Carbon Stored (metric tons/acre)
Tropical upland 100
Temperate 120
Boreal 130
Mangrove forests 400

Total Carbon Stored

Total storage: 4 to 20 billion metric tons

Global carbon emissions from fossil fuels in 2009:  8 billion metric tons (source)

Rate of Carbon Uptake by Forest

Rate of carbon burial compared to other tropical forests: up to 50 times faster (source)

Forest Type Annual Burial Rate of Carbon (g/m2)
Tropical upland 2 to 3
Temperate 1 to 12
Boreal 1 to 2
Mangrove forests up to 115
Sources: International Union for Conservation of Nature [pdf] and American Geophysical Union

Mangroves Around the Globe

Extent of mangrove forests as of 2000: 137,760 square kilometers or 0.7 percent of all tropical forests (source)

Extent by country: the largest extent, at about 23 percent of global total, is in Indonesia; just 15 countries (including Indoesia) hold 75 percent of global total (source)

Lost Mangroves

Percentage of world’s mangroves lost over last 50 years: 30-50

Amount of carbon released annually from degradation and deforestation: 20 to 120 million metric tons or 10 percent of global emissions from deforestation (source)

Man oh man, want those mangroves back.

Related Links

Mangroves Slide Show by the U.S. Geological Survey

filed under: Asia, carbon dioxide emissions, climate change, coasts, ecosystems, faculty, forests, global warming, oceans
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