Carbon Stored in Mangrove Forests
Research Institute
Ryuichi Tabuchi
Tama Forest Science Park
Forestry and Forest Products Institute
Background and Purpose
It is clear that the forest can store carbon and reduce carbon dioxide (CO2)
concentration in the atmosphere. So it plays an important role in global warming.
Mangrove forest has a high possibility of carbon storage. It grows up at the areas such
as tropical and subtropical shores, which are submerged when the tide comes in. Right
now, the area of worldwide mangrove forest is less than 20 km2 and accounts for less
than 1.5% of tropical forests. However, with abundant fresh water from deep mud rivers
and rainfall, the growth speed of mangrove forests is not slower than other land forests.
At same time, these forests have the same possibility of carbon storage. Because
mangrove forests are frequently submerged, and their dead roots in wet mud do not
decompose, they store a lot of carbon in peat form. In order to protect these important
mangrove forests, we examined how much carbon they can store in one year at the west
coast of Thailand and Malaysia, Malay Peninsula in Southeast Asia and Pohnpei Island
in Micronesia.
Achievements and Features
Two mangrove forests
In Southeast Asia such as Thailand and Malaysia, mangrove forests are harvested
for charcoal every 30~40 years, and then regenerates naturally. Because Pohnpei Island
is sparsely populated, there are many natural mangrove forests. Although it varies from
forest to forest in Pohnpei Island, carbon (converted value of total wood weight per
hectare) is estimated at about 160~300 tons, and in the young forests of Southeast Asia
which is comparatively younger by about 7~50 years at about 40~290 tons (Figure 1).
Carbon accumulation rate is 0~3 tons per year for Pohnpei Island and 0~9 tons for
Southeast Asia (Figure 2)
Old forest and forest in use
When forests grow up, the number of trees per area (forest stand density) will
decrease, but the total weight of the forest will increase greatly. It is known that the
total wood weight in Pohnpei Island is many times than in Southeast Asia even with the
same forest stand density. This is because the forests in this island have not been cut
down for a long time. With about 2,000 tons per hectare, old forests store more carbon in
peat form. Compared to mangrove forests, the most carbon that land tropical forest can
store in subterranean parts is about 500 tons because it has no peat. So mangrove
forests not only directly support a coastal inhabitant’s life, but also restrain global
warming. However, about 1,000 km2 of mangrove forest is lost every year. It is
necessary to regenerate this forest.
Photo 1. Mangrove in Micronesia (Rhizophora stylosa)
Figure 1. Relationship between mangrove forests in Southeast Asia and Pompeii Island,
Micronesia and carbon amount above ground (more carbon in Pompeii Island than in
Southeast Asia (with more young forest) for the same forest stand density)
Figure 2. Relationship between carbon above ground and annual carbon accumulation
rate for mangrove forest in Southeast Asia and Pompeii Island, Micronesia (When big
trees die, the carbon accumulation rate can go negative. The accumulation rate of young
forest (less carbon) is great. )