The largest mangrove forest of the world
By
dr.Fourkan Ali
“If there is no mangrove forest, then the
sea will have no meaning. It is like having a tree without roots, for the
mangroves are the roots of the sea.” -
A fisherman on the coast of the Andaman Sea.
The
Sundarbans is the largest contiguous block of mangrove forest remaining in the
world, Along the mouth of the Bay of Bengal, it extends over 10,000 square kilometers
in Bangladesh and India Some 60 percent of the forest lies in Bangladesh an the
rest in the Indian state of West Bengal. Said to be named after its maiden
Sundari tree species, the Sundarbans is a globally significant ecosystem rich
in bio-diversity providing habitat for around 554 plant and 453 animal species,
including the world famous Royal Bengal Tiger Several critically endangered
species like rare sharks also find refuge in this forest containing Sundari,
Gewa, Goran, Keora, Passur Baen and many other trees and plants.
Besides
its ecological value, more than four million people who live around the
Sundarbans derive part of their subsistence extracting resources including
fisheries, fuel wood, and non-wood forest products like honey Livelihood of
million others also indirectly depends upon this rich forest.
Every
year a good number of tidal surges hit Bangladesh’s south and south-western coastline and the Sundarbans
bears the brunt acting as a vital barrier against all such calamitous lashings
of the nature to protect the country's southwestern coastlines including the
regional towns and cities like Mongla and Khulna.
What is mangrove forest
"One
perceives a forest of jagged, gnarled trees protruding from the surface of the
sea, roots anchored in deep, black, foul-smelling mud, verdant crowns arching
toward a blazing sun...Here is where the land and sea intertwine, where the
line dividing the ocean and continent blurs, in this setting the marine
biologist and the forest ecologist both must work at the extreme reaches of
their disciplines." That was how the Scientific American, a US specialized journal, described the mangrove forest in
its March 1996 issue.
Growing
in the inter-tidal areas and estuary mouths between land and sea, mangroves,
able to tolerate saline water, provide critical habitat for a diverse marine
and terrestrial flora and fauna Healthy mangrove forests are key to a healthy
marine ecology.
Mangroves
are the consequential product of the inter-relationships of flora, fauna,
aquatic and water resources in certain natural conditions. The combinations of
the resources and conditions, occupying the special ecological niche where
seawater meets freshwater and fertilized periodically by sediments from the
land and sea, are the foundation of its high biological productivity,
uniqueness and diversity.
Mangrove
forests are vital for healthy coastal ecosystems. The forest detritus,
consisting mainly of fallen leaves and branches from the mangroves, provides
nutrients for the marine environment and supports immense varieties of sea life
in intricate food webs associated directly through detritus or indirectly
through the plank tonic and epiphytic algal food chains. Planktons and benthic
algae are primary sources of carbon in the mangrove ecosystem, in addition to
detritus. The shallow inter-tidal reaches that characterize the mangrove wetlands
offer refuge and nursery grounds for juvenile fish, crabs, shrimps, and
mollusks, Mangroves are also prime nesting and migratory sites for hundreds of
bird species.
Mangrove
forests are comprised of taxonomically diverse, salt-tolerant tree and other
plant species, which thrive in inter-tidal zones of sheltered tropical shores,
"over-wash" islands, and estuaries. Mangrove trees have specially
adapted aerial and salt-filtering roots and salt- excreting leaves that enable
them to occupy the saline wetlands where other plant life cannot survive.
Often
described as "rainforests by the sea," the mangroves are estimated to
cover an area of 22 million hectares, dominating the majority of the
subtropical and tropical coastlines around the world. However; over the past
several decades, the global area in mangroves has greatly diminished as a
result of a variety of human activities, such as over harvesting, freshwater
diversion and conversion to other uses.
Mangrove
forests literally live in two worlds at once, acting as the Interface between
land and sea. Mangroves help protect coastlines from erosion, storm damage, and
wave action. Thus the stability mangroves provide is of immense importance.
They prevent shoreline erosion by acting as buffers and catch alluvial
materials, thus stabilizing land elevation by sediment accretion that balances sediment
loss. This way they also protect vital coral reefs and sea grass beds from
damaging siltation.
World’s largest mangrove forest
The
main feature of the Sundarbans, which is likely to mesmerize a lone tourist, is
its unique silence. Without doubt, one‘s first impression of me dense forest
will be its great silence. Forest creatures are very shy, but as the visitor picks his
way along the trail or the water bodies around which occupy one third of the
Sundarbans Reserve Forest (SRF), he will realize how alive it is. Numerous
living organisms are discreetly watching and waiting whilst one passes through
their protective home. From time to time, the complete tranquility will be shattered
by a darting forest bird or a group of noisy monkeys jumping through the trees,
disturbing the secretive residents and setting up a chain reaction when the
ever-wary forest comes to a colorful and boisterous life for a moment, until
silence reigns again.
Mangroves
across the world are not particularly diverse in terms of their floristic
composition, especially compared with rainforest ecosystems. While up to 75
species are recognized as genuine mangrove plants, the floristic composition of
the Sundarbans is made up of 60 plus species. According to International Union
for Conservation of Nature (IUCN) no other mangrove ecological niche in the
world offers such a variety of associate mangrove vegetation as the Sundarbans does.
Historical
records reveal that during the medieval period, the northern boundary of the
Sundarbans extended from Hatiagargh, south of Diamond Harbor on the Hoogly river to Bagerhat, south of Jessore and
Haringhata along the southern part of Fakirhat, Satgaon and Khalifabad. During
the later part of the 18th and early 19th centuries, the boundaries of the
Sundarbans tract extended for about 273.55 kilometers along the shoreline of
the Bay of Bengal from the estuary of the Hoogly river to that of the Meghna
and inland up to a distance of 96.54 to 128.72 kilometers. According to a 1998
study carried out by UNDP/FAO sponsored Forest Resources Management Project
(FRMP), the total area of the SRI-1 representing three wildlife sanctuaries is
6017 square kilometers stretching over the districts of Khulna, Patuakhali,
Bagerhat and southern part of Satkhira. Of the total SRE 3997 square kilometers
is forest area, sandbars or grass covers 115 square kilometers and the rest
1905 is occupied by a number of rivers or channels.
With
expansion of human settlements and' reclamation of land for agricultural use, a
large part of the forest was cleared in between 1830 and 1875, when parts of
the mangroves were declared as resented forest i.e. the SRI-1 Since then the territorial
integrity still remained almost intact, in sharp contrast with many other
mainland "protected" areas in the country Despite large scale
indiscriminate felling of trees due to management problems, the natural
regeneration prom has kept the SRF alive and growing all die time. While all
other forests in the world are being more and more technically managed and
their soil productivity regeneration of plants, reproduction of wildlife are controlled
and monitored regularly as they are tending to lose their erstwhile individual
characteristics, die SRF is continuing to evolve new and newer biogeochemical
cycles. However, it is also clear that the well-defined boundaries of rivers
and canals, and perhaps the presence of widely feared what the local traditionally
refer to as "maternal uncle" (the Royal Bengal Tiger) have added significantly
to protecting the forest.
The ecology of the Sundarbans
The
Sundarbans soil is characterized as moderately to slightly saline zone in the
east and highly saline zone in the west. Its ecosystem is characterized by a
very dynamic environment due to the effect of tide, flooding, salinity and even
the cyclone. The fragile and intricate mangrove ecosystem depends on many
variable components like tides, salt contents in water and soil, duration of
sunlight, contents of sediment and organic matter in water; temperature and
density of seawater and fresh water. The composition of terrestrial and marine flora
and fauna also plays an important role in die mangrove ecosystem. If sun is
regarded as the source of all energy flow water must be considered as the
nursing mother of an ecosystem.
In
the Sundarbans, the flow of fresh water received from the tributaries of the Ganges
(Padma) is lighter in turbidity than that of the Bay of Bengal waters. The temperature of the two waters also varies seasonally.
The fresh water carries loads of mineral and microbe-rich silts, which do not
flow easily into the tidal backwaters from the sea as the influence of the
tides make the water flow back and forth. The mixture of the flows of fresh
water and brackish water and the mineral-microbe silts from upstream and due
forest wastes like over mature leave creates an ideal environment for different
mangrove organisms.
As
the forest litters and other organic materials are transported in the channels
the microorganisms like bacteria and fungi starts to decompose them convening
tl1em into minerals and nutrients. These are then used by phytoplankton and
insects like acron worms, nematodes and amphipods. In turn the micro organisms
themselves become a source o food for small aquatic animals, which too are preyed
upon by shrimps, crabs etc. The zooplanktons are again the food source for
different aquatic animals like fishes, catfish, eels, groupers and giant sea
perches. The planktons also provide food to sharks, crocodiles, and dolphins.
In this process some die, decay and become nutrients accumulated in the
mangrove soil. The amphibians and the reptiles act as connecting agents between
water-based energy flow and terrestrial energy flow In the Sundarbans, the
higher order animals like the tiger wild boar and monkey supplement their diet
by eating aquatic animals and fishes.
“Zonation"
often characterizes mangrove forests. Certain tree species occupy particular
areas, or niches, within the ecosystem. Some mangrove species occur close to
shore, fringing islands and sheltered bays; others are found further inland, in
estuaries influenced by tidal action.
The largest mangrove forest of the world
is under threat
Mangrove
forests are one of the most productive and bio-diverse wetlands on earth. Yet,
these unique coastal tropical forests are among the most threatened habitats in
the world as experts’ fear they may disappear more quickly than inland tropical
rainforests because of lack of public notice. The Sundarbans too is no
exception.
Most
experts agree that due to direct and indirect impact of human interventions,
far-reaching changes are taking place slowly but steadily -- affecting the
delicate Sundarbans ecosystem. Much of such changes are not clearly visible.
Direct human impacts are further worsened by the less-readily detected but
perhaps more menacing impacts which threaten the mangrove ecosystem. Massive
changes in both the adjacent agricultural lands and upstream areas with
construction of polders, embankments or barrages are feared to have been
generating fundamental changes in the hydrological regime of the Sundarbans.
The
changes in freshwater flushing are visibly caused by gradual eastward shift of
the flow of the Ganges river, The change is acknowledged as being historical
in nature although the more recent impact of e Farakka Barrage in India and subsequent siltation in the Gorai is accelerating
the process. It is believed that the changes affecting the salinity flood
intensity and periodicity erosion, siltation. and sedimentations may all be
factors for perplexing and worrisome loss m the world's largest mangrove
system.
A
number of species like Javan rhinoceros (Rhinoceros sondaicus), water buffalo
(Bubalus bubalis), swamp deer (Cervus duvauceli), gaur (Bos gaurus), hog deer
(Axis porcinus) and marsh crocodile (Crocodilus palustris) became extinct
during the last 100 years from the Sundarbans.
The
Royal Bengal 'Tiger is an inseparable part of the legend attached to the
Sundarbans. The tidal mangrove forest is a rare habitat for this tiger species.
But today they have been pushed due to habitat shrinkage. The SRF tiger
population estimate in the past 20 years remained in the range of 550 to 400,
the largest discrete population of the species in a single tract of natural
habitat in the world.
But
the preservation of the Royal Bengal Tigers is, by far; the most important
challenge for those concerned for the protection of Sundarbans bio-diversity
This challenge has become even more compelling of late with recent media
reporting of the outcome of a tiger population in the Indian part of Sundarbans
where the number of tigers was once estimated at something similar to that in
the Bangladesh part - i.e. 300+. The figure is now down to some 50 only.
Incidental
mortality due to diseases, illegal hunting and subtle changes in the Sundarbans
ecosystem poses a serious risk for the survival of the Royal Bengal Tiger Apart
from that, the interaction with humans in the area particularly the killing of
humans by tiger complicates the management of the area. IUCN has listed it as
an endangered species in its Red Book.
The
marsh crocodiles, once abundant, are already extirpated. The salt- water
crocodile (Crocodiles porous) still survives in low densities and like the
marsh crocodiles its population is being reduced through indiscriminate hunting
and trapping for skins, quite apart from the immediate conflict with men.
Despite an apparent reduction in illegal trade in its skin, the population
shows little sign of recovery.
Some
30 species of snakes have been recorded in the SRF and there appears to have
been a general decline in densities or at least in their sighting particularly
in the past two decades. The Rock Python (Python molars) is one of the valuable
SRF snake species, which is said to have declined over recent years. IUCN has
listed it as a "vulnerable species."
The
results of four independent inventories undertaken over the past seventy years
indicate that the overall volume of wood per hectare has decreased. Moreover;
closer analysis of three inventories undertaken in 1959, 1983 and 1996 indicate
a marked reduction in total standing volume for the two principal species of
economic importance, Sundari and Gewa.
According
to studies carried out at different times by the forest department, British ODA
and UNDP/FAO sponsored Forest Resource Management Plan, the mean volume per
hectare of the Sundari tree was 54.5 in 1959. The volume was reduced to 19.9 in
1985 and 17.8 in 1996. In case of Gewa, the mean volume per hectare was 8.7 in
1959, which was reduced to 4.6 in 1985, and 2.1 in 1996. The dramatic decrease
is blamed on their over exploitation, legally and illegally because of their commercial
value and subtle changes in the ecosystem. A number of issues related to the
Sundari, Gewa and Goran trees have emerged for immediate concerns of the
foresters.
According
to experts, the reasons for the decline in Sundari (Heriteria fomes) are twofold.
First, as a valuable timber species with real commercial value, it has been subject
to heavy exploitation. Second, increasing salinity as a subsequent impact of
the subtle ecological changes, noticeable increase in salinity and siltation
have resulted in hostile anaerobic conditions in which the Sundari finds it
difficult for healthy respiration. This has resulted in die-back whereby the
tree is progressively defoliated from the top downwards. The phenomenon, in act
an infectious disease, is called "top dying," The infectious top- dying
disease of Sundari causes another management problem as experts said poor
execution of infected trees invalidate the basic rationale for the
"sanitation/salvage" method to save the uninfected trees. Long delays
between marking and cutting causes more trees in an area affected by top dying
eventually exposing them to "axes instead of saws."
With
regard to Gewa, forest officials say high pressure from deer population in some
areas of forest patches have spared or caused nil regeneration of the species,
leaving the areas under-stocked. The decline in Gewa (Excoecaria agallocha) is
largely attributable to harvesting of around 50,000 m3 per annum as feedstock
to Khulna Newsprint Mill for the production of newsprint over the years.
Experts
say there is apparently little respect for the basic rule of leaving one stout
stem to aid re-growth while cutting Goran trees, the second largest tree
species of the SRF as all available merchantable stems are being cut from one
area. Some officials admit there is also Goran cutting going on outside the coupe
areas, including the wildlife sanctuaries. However, acknowledging the
importance of forest resources exploitation on a sustainable basis, the Forest
Department imposed a logging moratorium in 1989 on all timber species except Gewa
in the SRE.
Many
factors contribute to mangrove forest loss, including the charcoal and timber
industries, legal and illegal logging, oil spill, tourism industries, unplanned
development protects, urban growth pressures, and mounting pollution problems.
However one of the most recent and
significant muses of mangrove forest loss in the past decade has been the
consumer demand for luxury shrimp, or "prawns", and the corresponding
expansion of destructive production methods of export-oriented industrial
shrimp aquaculture along the forests.
No
discussion of the ecology of the SRF would be complete without noting the
problem of water pollution, Pollution from various sources is a major determinant
of water quality -- both in reverie and coastal areas of the Sundarbans. As
approximately one third of the nearly 600,000 hectares of the Sundarbans area
consists of tidal channels, and most of the reminder is subject to periodic
inundation, impacts of water pollution are potentially very widespread,
Pollutants are carried into the Sundarbans and ultimately into the Bay of
Bengal from various upstream sources including the industrial units, municipal wastes,
agrochemicals and port sewages in the Mongla and Khulna region.
The
main threat today may come from outside the area in the form of pollution. On
the northern edge of the area, Mongla,
Bangladesh second seaport is situated, this port and its
associated marine traffic is a frequent source of oil spills and there is a permanent
risk of, accidents with chemicals. Moreover toxic products (pesticides, etc.) enter
the system due to upstream pollution in the huge Ganges
catchments. Pollution may not be a direct source of mortality, but it may also
reduce the health of the forests, increasing the mortality rate of the flora
and fauna on the long term. Many products such as pesticides have also been
proved to reduce the reproductively (birthrate) in animal populations.
Almost
all Khulna-based industries like the match factories, fish processing plants,
jute mills, steel mills, the Khulna Shipyard and newspaper mills discharge
liquid or solid wastes directly into the Bhairab-Rupsha river system. According
to a DOE paper, the Khulna Newspaper Mills alone is estimated to use and
discharge 50,000 m3 of processed water laden with chlorides and dissolved and
suspended solids everyday along with the municipal wastes of the regional
cities.
Oil
spills during transfer of refined petroleum from tankers to receiving stations
in Mongla and Khulna, fuel oil spillage and discharge of oily ballast and
sewages from some 600 ships anchored in Mongla Port and residual heavy oil sludge, lubricants and engine
oils discharged during ship breaking operations in Khulna are major sources of water pollution affecting the
Sundarbans.
A
future threat is the exploitation of mineral gas, which is abundant in the
underground of the Sundarbans, The recent government decision to allow
exploration by international oil giants in the area has caused added concerns,
as mangrove environments are known to be the most vulnerable coastal habitats
to such activities.
A
very densely populated area surrounds the SRE around 1.2 million local users
reside seasonally in the area for fishing and outer resource use activities.
Commercial hunting was a problem mainly before the 19705 and this resulted
particularly in a serious depletion of the crocodile populations and to a
lesser extent to the deer population, Although wildlife protection has improved
significantly in the last decades, illegal hunting is still occurring on an
incidental basis and fishery is having an adverse impact on the remaining
turtle and crocodile populations as these animals are frequently caught up in fishing
nets.
Due
to natural processes the role of the Sundarbans to discharge the water of the Ganges
and Brahmaputra catchments is decreasing as main waterways are
shifting eastwards. As a result, the salinity of the Sundarbans is increasing
-- particularly in the western region. Further, the total annual discharge is
decreasing due to intensifying land use (dams, irrigation) upstream. The role
of this change is not yet clear, but is evident that it will influence wildlife
populations and vegetation in the long term,
The
expanding shrimp farming in the greater Khulna region has caused wide concerns for the rich
bio-diversity of the Sundarbans. Experts say indiscriminate shrimp and salt
cultivation already destroyed the valuable mangrove forest in Chakoria
Sundarbans and fear that the ecosystem of the SRF too would be in jeopardy for
the same reason in the near future. The fisheries department reckons that some
200 billion different fish fries are destroyed every year in course of
gathering two billion shrimp fries from the water bodies along the Sundarbans
due to the crude methods adopted for the purpose.
Several
international reports suggests that vast tracts of mangrove forests
particularly in Latin America, Africa and the Pacific Islands have been cleared
to make way for the establishment of coastal shrimp farm facilities. The
failure of national governments to adequately regulate the shrimp industry and
the headlong rush of multilateral lending agencies to fund aquaculture
development without meeting their own stated ecological and social criteria,
are other important pieces to this unfortunate puzzle.
The
great earnings from the shrimp sector are short-lived, while the real posts of
shrimp culture in terms of consequent environmental ruin and social disruption
are long-term and astronomical. While the immediate profits from shrimp farming
may satisfy a fog vast numbers of coastal residents, once dependent on healthy
coastal ecosystems for fishing and farming, are being displaced and impoverished.
Observers believe that the environmental and social losses would eventually
eclipse profits from the shrimp sector.
Forest
department officials admit that though slowly far-reaching changes are taking
place pervasively in me Sundarbans. These arise from direct and indirect
impacts of human influence in the area causing widespread quantitative and
qualitative degradation of the resource base throughout the Sundarbans
eco-system, According to forest inventory it is clear that the level of illicit
takeoff, some purely illegal and some quasi-sanctioned, may be quite larger
than what could be scientifically justified for sustainable management of the
SRF.
The
expanding tourism trade is appearing to be another major concern for the
protection of the Sundarbans. Except the conscious tourists or tour operators,
others tend to knowingly or unknowingly disturb the delicate ecosystem of the
Sundarbans staging bonfires, playing loudspeakers or disposing of
non-degradable wastes like polythene inside the forest, sea shores or water
bodies. That should be stopped.
Consequence of mangrove deforestation
In
many areas of die world, mangrove deforestation is contributing to fisheries
declines, degradation of clean water supplies, Stalinization of coastal soils,
erosion, and land subsidence, as well as the release of carbon dioxide into the
atmosphere. In fact, mangrove forests fix more carbon dioxide unit area than
phytoplankton in tropical oceans. With regard to the Sundarbans, experts have
sounded caution that destruction of the forest will not only affect the ecology
but cause far reaching impacts on national economy and causing immense damage
to the marine resources of the Bay of Bengal, still economically unexplored and
unexploited by Bangladesh. The loss of the Sundarbans would also expose the
entire southwestern region of the country to frequent cyclones and tidal
surges.
Mangrove
forests once covered three-fourths of the coastlines of tropical and
sub-tropical countries. Today less than 50 percent of that is surviving. And
then again, of this remaining mangrove forests, over 50 percent has been
degraded and not in good form, Greater protection measures should be taken for
maintaining high quality mangrove forests like the Sundarbans - a World
Heritage Site. All said and done, future sustainability of the Sundarbans
depends upon the political will of the policy makers, environmental awareness
of the people and the improved management and conservation by the forest department
and other concerned agencies.
Dr.Fourkan
Ali
Mob:
01711579267,
Email- dr.fourkanali@gmail.com
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