Agriculture Reference
In-Depth Information
and changes in these can lead to changes in mangrove species composition. Different
species may be able to move into new areas at different speeds making some species
capable of accommodating a higher sea-level rise rate than others (Semeniuk
1994
).
4.9 Mangroves and Carbon Sequestration
Mangroves are among the most productive primary producers and are important
carbon sink. In recent years, they have also been considered very important in rela-
tion to carbon sequestration. Mangroves have high carbon sequestration potential
through high biomass productivity. Studies have reported high standing biomass,
annual litterfall and net productivity of mangrove forests and have shown that these
are almost equal to some natural Dipterocarp forests (Whitemore
1984
). Jin Eong
et al. (
1995
) have reported that out of the total standing biomass of 114 tera C per
hectare, 74 % is in trunk, 15 % in roots and 10.6 % in canopy. Eong (
1993
) while
highlighting production of 18 t dry matter per hectare per year mentioned that if
disturbed, mangrove turn out to be CO
2
sources rather than sinks. Mangroves fix
17 tera C per hectare per year compared with 12 tera C per hectare per year by tropi-
cal forests.
Mangroves are also one of the nature's best ways for combating global warming
because of their high capacity for sequestering carbon. This is a characteristic of
mangrove wetlands that now demands our most immediate and undivided attention.
One of the greatest contributions that mangroves may have to offer is their great
propensity to sequester carbon from the atmosphere and store this in their wetland
substrate. According to the February 2007 issue of
National Geographic
, “Man-
groves are carbon factories…. Measurements suggest that mangroves may have
the highest net productivity of carbon of any natural ecosystem (about a hundred
pounds per acre per day)…”.
This combined lack of conservation ethics, shortsighted greed and weak law
enforcement have allowed massive losses of these coastal wetlands, with one huge
and hidden cost arising from the oxidation and release of stored mangrove carbon.
In a study conducted by Dr. Ong of University Sams in Malaysia (2002), it was
found that the layers of soil and peat composing the mangrove substrate have a high
carbon content of 10 % or more. Each hectare of mangrove sediment might contain
nearly 700 t of carbon per meter depth. In building large numbers of shrimp farms
or tourist complexes, the resultant clearing of mangroves and subsequent excava-
tion of the mangrove substrate could result in the potential oxidation of 1,400 t of
carbon per hectare per year.
Again, according to Dr. Ong, “Assuming that only half of this will become oxi-
dized over a period of 10 years, we are looking at the return of 70 tons of carbon
per hectare per year for 10 years, to the atmosphere. This is some 50 times the se-
questration rate. This means that by converting a mere 2 % of mangroves, all of the
advantages of mangroves as a sink of atmospheric carbon will be lost…”.
According to a latest study by the UN's Food and Agriculture Organization
(FAO), the current rate of mangrove loss is around 1 % per annum—or around
