Review of mangroves as blue carbon sink - - -
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Mangroves under Pressure: Forgotten Wetlands in the Changing Climate
Dr. Chandra Silori tells us why mangroves need to receive more
attention in international climate change negotiations, laying out the
many benefits provided by these “blue carbon sinks.”
Mangrove forests in Pred Nai, Trat province, Thailand.
2012/12/07 - This was the theme of one of the side events on Forest Day 6 in Doha
on December 2, 2012. A panel of well known coastal and marine
ecologists, sociologists, policy makers, and environmentalists in Doha
shared their thoughts and reminded everyone present about the importance
of the mangrove and other marine ecosystems in climate change
mitigation and adaptation. The capacity of mangroves, seagrasses, and
salt marshes to sequester carbon dioxide from the atmosphere and deposit
it in a reservoir is becoming increasingly recognized at the
international level. Of all the biological carbon, also termed as “green carbon” captured in the world, over half (55%) is captured by marine living organisms, also known as “blue carbon.”
Mangroves, salt marshes, and seagrasses form much of the earth’s blue
carbon sinks. They store a comparable amount of carbon per year to that
of all other plant biomass on land. Quoting the findings of a study
conducted by a team of researchers from the U.S. Forest Service’s
Pacific Southwest and Northern research stations, University of
Helsinki, and CIFOR, one of the panelists shared that per hectare
mangrove forests store up to four times more carbon than most other
tropical forests around the world.
Research attributes this ability of mangroves to store such large
amounts of carbon, 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.
However, despite such a substantial role of mangroves in absorbing
atmospheric carbon, all the panelists unanimously agreed that mangrove
forests have yet not been given due attention in the global debate on
climate change. They need much more attention in the UNFCCC climate
change talks, on the level of that given to other forest ecosystems,
such as terrestrial forests and peat lands. Interestingly, in a way,
mangroves combine both, tropical and peat land forests together, and
have the highest productivity of any forest ecosystem on earth.
Mangroves perform a variety of useful ecological, bio-physical, and
socio-economic functions. They not only serve as breeding grounds for a
variety of fishes and other marine fauna, but also protect the
inhabitants of coastal areas during natural calamities such as storms,
typhoons, and tsunamis, by serving as natural barriers. Such natural
calamities are projected to increase in future due to increased
anthropogenic pressures, and climatic changes. From a socio-economic
point of view, mangroves provide a variety of benefits. Serving as a
breeding ground for fishes and other marine fauna, they provide an
income source to the local fishermen communities, while mangrove wood is
used to make charcoal and also as wood fuel for cooking. Values of
mangroves for honey, fodder, edible seeds, and medicinal properties have
also been documented widely.
Thus mangrove forests play both, mitigation and adaption functions in the changing climate.
But unfortunately mangroves are being rapidly destroyed all over the
world, at a higher rate than tropical forests. The range of
anthropogenic pressures on mangroves are on a constant increase. For
example, Southeast Asia, which has 22% of the total mangrove cover in
the world – the largest share amongst all the 124 countries in the
world – faces severe pressure from commercial shrimp farming and
charcoal making. Every year thousands of tons of shrimps are exported to
the western markets. Looked at another way, this means transporting
carbon to these countries, as shrimps are reared at the cost of cutting
down thousands of hectares of mangroves. Due to the cutting down of
mangroves, the wet soil dries up very quickly, releasing more carbon
into the atmosphere, at a substantially higher rate, as mangroves have
more carbon in their soils. Estimates suggest that a range of between
150 million to 1 billion tons of CO2 is emitted annually due to the
destruction of mangrove forests globally. All these are important
factors to consider when pushing the agenda forward to include mangroves
in climate change mitigation and adaptation frameworks.
In this context, RECOFTC’s work in promoting community based
conservation of mangrove forests in Pred Nai village, Trat Province on
Thailand’s eastern sea board (through its Thailand Country Program) is
an important intervention and contribution to promoting a participatory
approach in the conservation and management of mangroves. The Thailand
Country Program of RECOFTC continues to work in Pred Nai village and has
recently initiated a grassroots level, community based learning center
there. This network of natural resources and environmental conservation
initiatives links and establishes communication between concerned units
at the provincial level and community members who play a vital role
toward natural resource conservation in Trat. These efforts also promote
policy support for local authority decentralization, and provide
technical and technological support to local officers on natural
resources management planning, and strategies on strengthening community
self-management. This is an important initiative to better understand
the roles of mangroves in local livelihoods and also for climate change
mitigation and adaptation at the local level.
