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Biodiversity and
Floristic Composition of Sundarbans in Bangladesh
By: M. N. Amin
The popularly known
Sundarbans, mangrove (tidal/littoral forest) forest of Bangladesh, is
undoubtedly the largest mangrove system in the world. The World Heritage
Committee of UNESCO in its convention concerning the protection of the world
cultural and natural heritage in Naples, Italy in 1997 inscribed the Sundarbans
as the world heritage site in Bangladesh. The forest is unique for supporting
an exceptional biodiversity with a wide range of flora and fauna and concurrent
functioning of the significant ecological processes; monsoon rains, flooding,
delta formation, tidal influence, and plant colonization and climax formation.
Sundarbans is bounded in
north by Bagerhat, Khulna and Satkhira districts, in the south by Bay of
Bengal; in the east by Baleswar (or Haringhata) river, Perojpur and Barisal
districts; and in the west by Raimanghal and Hariabhanga rivers, which
partially form the boundary of Bangladesh with West Bengal in India. At its
maximum extent the forest is about 70 miles wide from north to south and about
180 miles long from east to west.
The socio-economic importance
of Sundarbans is enormous. It supports many industries as well as local economy
and communities by supplying raw materials, and employing people for their
subsistence and livelihood. The forest is acting as shelterbelts against
natural calamities like storms, cyclones and tidal bores thus protecting the
establishments and properties of the people inhabiting in coastal areas from
such activities. The environmental importance of the forest is also worth
mentioning. Some of the important socio-economic services of the Sundarbans are
described briefly in the following paragraphs:
It is often said that most
part of Bangladesh was originally well vegetated, with coastal mangroves backed
up by swamp forests and a broad plain of tropical moist deciduous forest.
However, more than 90% of the original vegetation has been cleared during the
last 50 years or so. Now the ecosystem is changing rapidly and biodiversity is
depleting fast with the extinction of some species of the forest. This changing
scenario of Sundarbans creates real concern to the responsible society.
The Sundarbans of Bangladesh
that extends westwards into India is the largest mangrove system of the world,
followed by the mangroves of Irian Jaya of Indonesia. An intricate network of
interconnecting waterways, of which the large channels in a generally
north-south direction, intersects the whole area. The Sundarbans provides ideal
habitats for a variety of unique plants and animals. The forest is rich in
biodiversity with about, 334 species of plants, 270 species of birds, 42
species of mammals and 210 species of fishes, including 32 species of prawns.
It is also famous for the natural habitat of a variety of wild animals, the
important among them are tigers, deers, wild boars, wild fowls, monkeys,
otters, crocodiles, birds, pythons, lizards, amphibians, molluscs, crabs and
different varieties of snakes.
Alongside the recorded 42
species of mammals, waders and seabirds find the Sundarbans as their suitable
habitats and also both marine turtles and the endangered estuarine terrapin,
Batagur baska find it as their suitable nesting site. But above all, the
Sundarbans is well known as the home of the famous Royal Bengal Tiger,
Panthera tigris, whose population is estimated at 350 to 600, one of the
largest surviving populations in the world.
The floristic composition of
Sundarbans, was first described by Prain (1903) with 334 species and 245 genera
in 75 families of plants including small to large trees, shrubs, climbers,
grasses and herbs. So far, no similar study and detailed inventory have been
made on the vegetation, although ODA (1985) has listed 130 species of commonly
found higher plants and Islam (1976) has reported 165 species of algal flora
from in and around the mangrove ecosystem. However, among various types of
plants some are endemic to the Sundarbans. The forest is rich in epiphytic
ferns, parasitic plants and orchids; among the 66 species of orchids found in
the forest about 13 are epiphytic.
The vegetation of Sundarbans
is unique in many respects such as floristic diversity, composition,
association and abundance. It is also interesting to note that tree height is
relatively shorter in South-Western parts and longer in North-Eastern parts of
the forest.
The forest has a glorious
past with a written history of more that one thousand years. It acts as a
natural safeguard to protect the entire coastal region at the north of
Sundarbans from cyclones and tidal bores. The environmental importance of the
forest as green shelterbelt can be assumed from the devastation and death toll
caused by such catastrophic events in the coastal areas where there is no
mangrove forest like Sundarbans. However, during the 1950s Sundarbans by and
large was not inhabited at all and most forest areas were virtually
inaccessible. However, mass destruction of the forest environment by human
efforts began during the early 1960s. According to one estimate the Sundarbans
had a total area of about 67O thousand hectares just a decade ago.
Unfortunately, we have lost more than one-third of its area during the recent
past that has reduced the forest area to about 420 thousand hectares. A major
recent change in the physical environment of the Sundarbans is a reduction in
the amount of fresh water flowing into the area that resulted in considerable
increase in salinity level. This is due to natural changes, river diversions,
and construction of dams and withdrawal of freshwater for irrigation. It is
believed to be one of the major causes of unusual mortality of the main
commercial species "sundari", in some areas especially since 1970. It seems
unlikely that the trend of decreasing freshwater discharge can be reversed;
indeed the problem is likely to be aggravated by a rise in sea level caused by
global warming. However, there have been considerable studies on environment
and conservation aspects of the Sundarbans. Nevertheless, there seems to be a
wide gap in implementing the recommendations of these studies as debates are
going on in the issues of continued environmental degradation and unscrupulous
harvesting of resources of the forest. There is, therefore, suggestions that
eternal social vigilance and resisting reckless exploitation of forest
resources, unplanned conversion of forestland for other uses and proper
implementation of the conservation policies thus far formulated can only save
our world heritage site. Under the threshold of unprecedented environmental
degradation and imprudent resource harvesting the Sundarbans still provides
every day earnings of millions of people, by working directly or indirectly on
the natural resources of the forest.
THREATS TO BIODIVERSITY
AND ECOSYSTEM
Plundering and unscrupulous
exploitation of the forest resources by the state as well as
production-oriented forestry system are said to be the main causes of forest
loss in Bangladesh and consequently threat to the biodiversity. Recurrent
natural calamities like cyclones and tornadoes are also big threats to the
forest. About one and half dozen of cyclones have hit against Sunderbans only
during the current decade. Alongside multifarious destructive anthropogenic
activities and natural calamities some ecological changes like increase in
salinity and sea level, and outbreak of diseases like top dying of trees occur
in the recent time that pose serious threats to the rich biodiversity of
Sundarbans.
Diversion of the natural
courses of rivers through training activities, and construction of embankments,
dams and bridges in the upstream as well as decreased flow of fresh water in
the rivers resulted in the increase in salinity level and over silting in many
places and subsequent changes in the mangrove ecosystem. Increased salinity and
over silting within the forest may hinder the biological functions of the
pneumatophores (breathing roots) and are supposed to be the major causes of top
dying of the trees. Possibility of infestation by the fungal pathogens cannot
be over looked. Dieback is also common in mesophytic plants like Guava and
Sisso after a short period of rain/ flood water stagnation, which is caused by
the Fusarium spp. that produce complex and fatal symptoms in the affected
plants, popularly called as "fusarium-syndrome". The following reasons have
been identified as major threats to the biodiversity of Sundarbans:
- Population pressure,
expansion of agricultural land, constructions of houses, roads, etc., and
grazing by domestic animals.
- Unscrupulous harvesting
of forest resources and insufficient measures to regenerate the resources.
- Indiscriminate use of
chemical fertilizers and insecticides in croplands and adoption of unplanned
agricultural practices.
- Lack of appropriate
policies for proper management and expansion of wild life sanctuaries
/protected areas.
- Lack of proper
education, training and research for implementing conservation strategy so
far recommended.
CONSERVATION NEEDS
Maintaining the biological
integrity of the forest ecosystems, whose importance we often appreciate but do
not as yet understand, presents difficulties to researchers developing a
sustainable management system especially under current levels of natural and
man made threats to the forests.. It is obvious that in recognition of the rich
biodiversity of the Sundarbans it has been declared as a World Heritage Site in
Bangladesh. The country is thus pledge bound to protect the treasure of natural
resources [both the biotic and abiotic] of the forest.
It is estimated that a number
of species among plants, fishes, reptiles, birds and mammals are threatened
with extinction for various reasons. Therefore, taking appropriate measures for
conservation of biodiversity in Sunderbans should be the highest priority.
However, to protect and conserve the rich biodiversity of Sundarbans three
wildlife sanctuaries (protected areas) have been established, these are
considered to be not sufficient to represent the delicate ecosystem of the
mangrove forest. There is an urgent need for a holistic and integrated approach
of biodiversity conservation involving in situ and ex situ strategies along
with community participation and use of indigenous knowledge en route to
biocultural restoration of the mangrove ecosystem.
In all considerations the
ecosystem of Sundarbans demands urgent and sustainable management.
Nevertheless, some interested groups are embarking on oil and gas exploration
in the Sundarbans. It is said that any exploration in the forest area must be
forbidden. If we fail to forbid such exploration that may lead us to a
catastrophic environmental condition where the very existence of the "Lush
Green Bangladesh" would surely be in jeopardy.
Dr. Muhammad Nurul Amin
is-Professor in Department of Botany at-University of Rajshahi,
Rajshahi-6205,-Bangladesh. |
