A Note On
Sea-Level
Rise in Bangladesh
By
Bashir A. Khan
INTRODUCTION
Bangladesh, which was a part
of Pakistan before 1974, is an important country of South Asian region. Its
most immediate neighbors are India and Myanmar. It is located at the upper side
of the Bay of Bengal. Bangladesh is the world's eighth-most populous country, the fifth most populous in Asia and the third-most populous among Muslim-majority countries(1).
Bangladeshi coastal plains or Bengal
Delta, are one of the most fertile
regions not only in South-Asia but also the whole of Asia or even the
whole of Earth and it includes three of Asia's largest rivers, including the Ganges (Padma), Brahmaputra (Jamuna) and Meghna. The Ganges delta is formed by the confluence
of the Ganges (local name Padma or Pôdda), Brahmaputra (Jamuna or Jomuna), and Meghna rivers. The Ganges unites with the Jamuna and
later joins the Meghna, finally flowing into the Bay of Bengal. The alluvial soil deposited by the rivers when they overflow
their banks has created some of the most fertile plains in the world (2).
The country is
also home to the Sundarbans, a sanctuary of the Bengal tigers and the world's largest mangrove forest. The eastern region includes a lush tea growing area and the mountainous Chittagong
Hill Tracts.
The country's 600 km (370 mi) coastline includes the world's longest
natural beach, a coral reef and numerous islands. The climate is prone to monsoon floods and cyclones. Bangladesh is one of the most densely populated countries in the world, ranking
alongside South Korea and Monaco(3).
Bangladesh is
predominately rich fertile flat land. Most parts of Bangladesh are less than
12 m (39.4 ft.) above sea level, and it is estimated that about 10%
of the land would be flooded if the sea level were to rise by 1 m
(3.28 ft.). It is estimated that ~17% of the country is covered by forests
and ~12% is covered by hill systems. The country's hoar wetlands are of significant importance to global environmental science(4).
Straddling the Tropic of Cancer, Bangladesh's climate is tropical with a mild winter from October to
March, and a hot humid summer
from March to June. The country has never recorded an air temperature below
0 °C, with a record low of 1.1 °C in the north west city of Dinajpur on 3 February 1905(5). A warm and
humid monsoon season lasts from June to October and supplies most of the
country's rainfall. Natural calamities, such as floods, tropical cyclones, tornadoes, and tidal bores occur almost every year(6) combined
with the effects of deforestation, soil degradation and erosion. The cyclones of 1970 and 1991 were particularly
devastating. A cyclone that
struck Bangladesh in 1991 killed some 140,000 people(7).
The land and the
people of Bangladesh have a long and rich relationship with water. The country
has many long and deep rivers and thousands of natural and man-made canals are scattered
throughout the land. The economy is primarily based upon fishing and
cultivating rice, jute, wheat and corn. The water is both companion and, occasionally,
a bitter enemy of the Bengali population throughout the history, but people are
brave and always faced the flooding problems with a smile.
Sea-Level Rise:
Causes and Affects
Climate
change is being widely discussed in the world due to its timely and immediate importance
for the humanity as a whole. However, some local regions are more prone to
climate change effects than others. The expanding industrialization and other
consequential human activities are making the world hotter and hotter every
day. The net result is what is generally called Global Warming. Actually both terms mean the same affect. It is
obvious that a consistent rise in atmospheric temperature results in the rise
of sea-water level.
This rise affects low lying coastal regions and inhabitants of the
respective deltas. Up to 1990 this concern had become so urgent that Intergovernmental Panel on Climate Change
made a collaborative study and estimated
that if the same pace of human industrial expansion is retained in the near
future the world would be 3.3ºC warmer by the end of the next
century (i.e., by ~2090). As a
consequence, with the rise in this much temperature, sea level will rise
appreciabely due to thermal expansion of water and glacier melting.
Bangladesh is a flood plain delta with a large number of rivers forming
a complex web of “water tubes”. Its geographic setting is such that it forms a
slope running from north to south. The whole coast runs parallel to the Bay of Bengal, forming about
710 km of coastline(8). Many
densely populated districts of the country are subject to direct affect by the
expected sea-level rise.
.
Fig 4: Glacier Melting Due to Global
Warming
This means that millions of people will be
directly affected by the dangers of level rise in the coming decades. The coastal zone covers some 47 thousand
square kilometers of land area, which comes out to be about 32% of total land
mass of the country. Water area covers some 370 km from the coastline,
estuaries and the internal river water. A wide industrial area called Exclusive Economic Zone (EEZ) is also
treated as a coastal zone.
Bangladesh is now widely
recognized to be one of the countries most vulnerable to climate change. Natural hazards that come from increased
rainfall, rising sea levels, and tropical cyclones are expected to increase as
climate changes, each seriously affecting agriculture, water and food security,
human health and shelter. It is believed that in the coming decades the rising
sea level alone will create more than 20 million climate refugees(9). Climate change
is causing increasing river erosion
in Bangladesh, threatening an estimated 20 million people.
During the twentieth century,
global mean sea level rose at an average of 0.07 inches (1.8 millimeters) per
year, but from 1993 to 2003, that rate increased to 0.12 inches (3.1
millimeters) per year. Scientists
attribute the rising sea levels to expansion of the oceans as they warm, as
well as to the melting of mountain glaciers and the Greenland and Antarctic ice
sheets(10, 11, 12). Bangladesh,
one of the world's most populous countries, is highly vulnerable to the effects
of sea-level rise—including more salinization of both ground and surface
waters. The deltaic plains of the Ganges, Brahmaputra, and Meghna rivers
compose most of the country's land area,4 and the
vast majority of the coastal zone is at an elevation of less than 16 feet (5
meters).
Local sea-level rise of as much
as 1 inch (25 millimeters) per year has been recorded in sections of the
Ganges-Brahmaputra Delta. Most deltas experience natural sinking and settling
of land (subsidence), which can increase relative, or local, sea-level rise.
Human interventions such as extraction of groundwater can speed up subsidence,
as has been the case in the Ganges-Brahmaputra basin. Local sinking and
groundwater extraction can allow seawater to creep inland, displacing coastal
plant and animal communities that depend on brackish or freshwater. Encroaching
seawater and salty groundwater may also increase soil salinity, which can
hinder growth of crops(13). For example, increased salinity inhibits
rice growth and can lower rice yield(14).
By mid-century, more than 3 million people
stand to be directly affected by sea-level rise in the Ganges-Brahmaputra Delta(17). In a
worst-case scenario, Bangladesh could lose nearly 25 percent of its 1989 land
area by around 2100. Climate change is projected to cause further
sea-level rise during this century and beyond. If we do nothing to reduce our heat-trapping
emissions, global
sea level is projected to increase some 23 inches (59 centimeters) over recent
average levels by the end of this century(18).
However, if we make significant
efforts to reduce emissions,
sea-level rise could be limited to about 15
inches (38 centimeters) by the end of this century. Recent
evidence of higher rates of global sea-level rise suggests that these
projections may be low. and
regional variations in sea-level rise are expected to continue(18).
In Bangladesh, the impact of
sea-level rise may be worsened by other effects of global warming, such as
variable precipitation, more frequent droughts and floods, and shrinking of the
glaciers that supply water to the rivers of the delta. Reduced rainfall during
the dry season, for example, can increase the salinity of rivers through
encroaching seawater that moves upstream during periods of low flow(19).
Human activities such as shrimp
farming and damming of rivers are also expected to intensify the effects of
sea-level rise. Dams can retain sediment that would otherwise replenish eroded
or subsided land in the river delta(15).
More dams are planned in Asia, which are likely to increase erosion as well as
relative sea-level rise, and might worsen water shortages and extend the area
affected by salinity during the dry months.(16).
With the added pressure of rising
air temperatures, rice production in Bangladesh could drop by 8 percent, and
wheat production by 32 percent, by the middle of this century(3,18).
Unless we act now to cut our heat-trapping emissions, and take steps to prepare
for the warming already projected to occur in the coming decades, the food and
freshwater supply of millions of people in the Ganges-Brahmaputra Delta is
likely to be in danger.
Response to Sea-Level Rise:
Adaptation & Mitigation
Nature is Nature and human
beings are so weak against it that individual and small scale effort to meet
the big natural challenges being faced by countries or big geographical regions
do not produce appreciable results. The challenges of sea level rise to the
coastal regions are so diverse, complicated and daunting that potentially no
nation, however economically fit, can stand to them in a short period (i.e., a
few decades) of time. Very extensive studies, plans and budgets as well as
civic understanding is involved along with a social and political will of the
people of the concerned region. Bangladesh is a small (area wise) country and
its populational and food problems are so daunting that it is almost impossible
for it to deal single-handedly with the effects of sea-level rise. The major
option for this region, in the opinion of the current writer, is to pay high
attention to minimize the effects of
the sea-level rise affects in the next two or three decades.
In the words of the main author
of the legendary paper on the preventive measures of the sea level rise(20),
only two options, Adaptation and
Mitigation, are available to communities facing this challenge. What does
these terms mean, can be quoted in the words of the main author as: “Mitigation is a response to the broad issue
of climate change and involves reducing or stabilizing greenhouse gas emissions
or levels, in order to mitigate changes in climate…….Adaptation refers to
adjustments in ecological, social and economic systems in response to actual or
expected climatic stimuli, their affects or impacts”.
The mitigation requires very big budgets while
adaptation can be done with lower expenses. For this poor country, Bangladesh, both
options are necessary while adaptation should be done first before mitigation as an immediate control measure. Adaptation is a local effort while mitigation requires co-operation of the
neighboring countries as well as the world community. But, How to implement
these measures ? Following is a brief discussion of both of these control
measures.
Adaptation:
The main goal of this strategy is
to minimize the effects of sea level rise on the living organisms of the area
including human beings. To address the sea level adaptation:
1. Government policies have to
be changed that could lessen pressure on all kinds of resources along with the
managerial control.
2. As most of the coastal
population depends on the fish-catching and agricultural farming, the
adaptation option should be stressed on these two sectors to overcome the
issues of the anticipated issues. A
practical solution is that the foreign exchange
earned by the coastal fisheries industry could be invested for the
development of coastal fisheries sector. This investment may be used for
disaster preparedness activities, special weather forecasting and further
research.
3. The fishermen and their young family members
should be specially trained and equipped with necessary tools to be used in the
event of disaster. A fixed amount of their income may be deducted and put into
government saving schemes which can be used by them in the difficult times of
disaster.
4. Cheap television and
cellular phone facilities may be provided to the coastal facilities so that
they remain always informed about the weather forecasts.
5. Since salinity is increased
with the rising sea level, good research in the universities and government
institutions may be done to find out salinity
tolerant grain and fish species. After creating and selecting different
salinity tolerant species the fishermen may be trained about breeding,
cultivation and harvesting of the species.
6. For the forests located near
the coastal areas new salinity-tolerant trees should be developed and
introduced. This could be done by investing into research, as indicated before.
Mangrove afforestation should be adopted to protect soil erosion because its
roots help to compact soil. The decomposition of dead leaves of mangrove will
add organic matter to the soil turning coastal land more fertile.
7. The research activities should also include
the development of raw materials for coastal resources dependent industries.
8. Efforts for fresh water
availability to coastal zone population may be enhanced as the coastal zone is
threatened by water born cholera and diarrhea diseases. The continuation of
good health of fishermen and farmers of the coastal communities is vital for
saving of budget which is otherwise spent on the maintenance of health
facilities than other useful sectors.
Mitigation:
It is often said that prevention is better than cure. It is fully true in all senses. Mitigation is
the act of prevention. To implement this option, the following is recommended
by the authorities of the field:
1. The control on the emission
of greenhouse gases is the prevention of climate change and ultimately the sea
level rise. Since industry is not much diverse in Bangladesh it emits a very
small amount of greenhouse gases, however, still it should try to cut it down
in the future when more industrial units are built in the country. Control of
deforestation and fossil fuel is necessary to achieve this goal.
2. Some of the greenhouse gas
emission reduction measures include
2.1
Demand reduction and/or
efficiency improvement
2.2
Substitution among fossil
fuels
2.3
Switching over to nuclear
energy option
2.4
Switching over to biomass
option
2.5
CO2 scrubbing and removal
2.6
Afforestation
3. The country should think to
seek and use possible renewable resources to generate electric power. In the
coastal areas and in many inland areas favorable natural conditions like
sufficient sunshine and wind speed exist for the promotion renewable energy in
the country.
4. As of solar power
generation, in Bangladesh average absorbable solar radiation is 0.193 kW/m2.
The country has an area of 144,000 square km. This means that The country
receives a constant supply of 28 TW5 energy from the sun, which is
nearly 200kW per capita for a population of 140 million. The annual per capita
consumption of electricity in Bangladesh is estimated as 112 kW, which is
available only for 18% of the population. Comparative to the present electricity
consumption, solar energy availability is a big amount of energy. A World Bank
survey reports that 500,000 households of Bangladesh may be potential market
for solar home System (21,22,23).
5. Afforestation in the coastal
zone has potentiality to increase forest cover in the country. An extensive
afforestation effort will act as carbon sink. For this purpose, as already said
elsewhere, mangrove plantation in the zone will be very beneficial means of
coastal protection against cyclones, storm surges and soil erosion
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