If there is no mangrove forests, 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 present day world. Along the mouth of the Bay of
Bengal, it extends over 10,000 square kilometres in Bangladesh and
India . Some 60 percent of the forest lies in Bangladesh and 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 334 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, fuelwood, 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 southwestern 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 specialised 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.
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 the 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 realise 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 tranquillity 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
colourful 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 recognised 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.
Despite large scale indiscriminate felling of trees due to management
problems, the natural regeneration process has kept the SRF alive and
growing all the 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, the SRF is continuing to evolve new and
newer bio-geo-chemical cycles. However, it is also clear that the
well-defined boundaries of rivers and canals and perhaps the presence of
widely feared what the locals traditionally refer to as "maternal
uncle" (the Royal Bengal Tiger) have added significantly to protecting
the forest.
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
characterised by a very dynamic environment due to the effect of tide,
flooding, salinity and even the cyclones. 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 the mangrove ecosystem. If sun is
regarded as the source of all energy flow, water must be considered as
the nursing mother of an ecosystem.
World's largest mangrove forest 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 the 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 to 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 350 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.
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 (Crocodylus porosus) 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
molurus) 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
34.5 in 1959. The volume was reduced to 19.9 in 1983 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 1983, 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 fact 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 invalidates 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
populations in some areas of forest patches have 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. 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 SRF.
Many factors contribute to mangrove forest loss, including the
charcoal and timber industries, legal and illegal logging, oil spill,
tourism industries, unplanned development projects, urban growth
pressures, and mounting pollution problems. However, one of the most
recent and significant causes 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 riverine 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.
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.)
and urban wastes enter the system due to upstream pollution in the huge
Ganges catchment. 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 (birth
rate) 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.
A very densely populated area surrounds the SRF. Around 1.2 million
local users reside seasonally in the area for fishing and other resource
use activities. Commercial hunting was a problem mainly before the
1970s 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 catchment 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 Chokoria 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. 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 the 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.
Consequence of mangrove deforestation
In many areas of the world, mangrove deforestation is
contributing to fisheries declines, degradation of clean water supplies,
salinization 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 per 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.