Chapter-5
EFFECTS OF SEA LEVEL RISE (SLR)
The predicted rises in sea level will be experienced through a number
of impacts, including the inundation of coastal areas, increased likelihood of
flooding in storm surge occurrences and substantial increases to the erosion
of coastlines. These impacts will be enough to adversely affect many
ecosystems including beaches, coastal wetlands and coral reefs. In some
areas these ecosystems will be forced to reduce in size and in others they
will be lost completely. These ecosystem losses will in turn impact on
human settlement reducing natural defence against rising sea level in periods
of storm surge. The degree at which the predicted sea level rise is expected
to have on nations varies, with some noticeably more vulnerable to this
environment issue than others. Even conservative sea level rise predictions
will devastate some nations, resulting in the loss of land and displacement of
many people. Coastal regions are some of the most diverse and productive
ecosystems as an active interface between land and water. However they are
currently reeling under immense pressure from a medley of stressors such as
rapid population growth, urbanization and development activities that alter
the structure and function of these ecosystems.
Climate change poses as an additional threat that varies both in the
severity of temporal and spatial impacts. In the coastal regions of West
Bengal current and projected vulnerabilities to the impacts of climate change
in general and sea level rise in particular are being assessed to work out
methods of dealing with them. This will help identifying target areas for
interventions to prepare for such changes. Uniquely placed in the eastern
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lowland area of the Bay of Bengal, bordering Bangladesh, the state of West
Bengal is vulnerable to any potential rise in the sea levels and thrusts from
cyclonic events and storm surges. Exposure to storm surges, monsoon and
post monsoon storms are comparatively high and make the state vulnerable
to the occurrence of such events. Besides, dense population, rapid
urbanization with high rate of degradation of local environments is
characteristic to most of the region. The Gangetic delta mangroves -the
Sundarbanss, formed at the confluence of the Ganges and the Brahmaputra,
is world's most extensive continuous mangrove forests and covers about
2000 sq Km in the Indian territory. Any impact to the coastal ecosystem has
a direct impact on coastal livelihoods. TERI is studying the effect of climate
related hazards like floods, cyclones and storm surges on the communities
residing in the region. Geographical Information Systems (GIS) is being
used for better identifying pockets vulnerable to hazards such as sea level
rise, floods, cyclones and storm surges. Additionally, vulnerability is being
assessed in terms of the level of socio-economic development of that region.
5.1 Physical (Environmental) Effects5.1.1 Loss of landmass and settlement
Policy changes needed to reduce vulnerability include limitations on
the sitting of new development or infrastructure (including transportation
corridors) in high‐risk areas. Also needed are changes to permit
requirements for setbacks and design elevations and modifications to
building codes for structural elements and corrosion‐resistant
equipment.Long‐term plans for maintenance, retrofits and upgrades should
incorporate opportunities for adapting existing infrastructure to projected
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changes in flood risk through elevation, relocation, increased capacity or
other measures. Emergency management planning must incorporate
increased demand for emergency services and consider sea level rise impacts
on evacuation routes. Use of state resources for repair or construction of
shoreline protective measures–whether natural or engineered, temporary or
long term–should be evaluated to ensure that they are the most cost‐effective, long‐term, site‐specific approaches feasible. Plans for back‐up
measures for critical systems such as energy and drinking water should
include impacts of sea level rise. Determinations of priority for remediation
of hazardous waste sites and brownfields should consider the likelihood of
increased flood risk. Residents of some areas may have to explore
alternative sources for drinking water should their primary sources be
degraded.
Table 5.1 Submerge areas due to see level rise in future.
See Level Rise in(m) Affected Costal Area in Percentage
west centre east
1m 0.1% 14% 21%
3m 4% 29% 38%
6m 32% 47% 59%
9m 49% 78% 94%
source;: Coastal Zone Development Authority
Non‐structural solutions, such as elevation and relocation of
structures, must play a major role in a statewide response, especially in less
urbanized areas where they may be less expensive and more effective at
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reducing long‐term vulnerability (Recommendation 5). Such strategies
include conserving natural systems such as barrier islands, tidal wetlands
and dune systems that currently provide flood protection and community
benefits at no cost. Low‐impact development and green infrastructure could
also help mitigate the effects of sea level rise, including flooding. Low‐impact development emphasizes conservation and use of on‐site natural
features to protect water quality. Green infrastructure refers to the use of
natural or engineered systems that mimic natural processes. It includes rain
gardens, rooftop catchment systems and green roofs, technologies and
practices that allow treated wastewater and storm water to infiltrate back into
groundwater systems rather than piping it into the nearest waterbody, where
it may exacerbate coastal flooding.Non‐structural solutions, such as
elevation and relocation of structures, must play a major role in a statewide
response, especially in less urbanized areas where they may be less
expensive and more effective at reducing long term vulnerability Due to
their escalating capital and maintenance costs and the incentives they create
for new development in high‐risk areas, reliance on structural protection
measures alone, as well as funding such measures, without examining
alternative or complementary solutions, should be significantly reduced over
time. State and federal support for shore defense measures will likely be
reduced and become uncertain in the future as sea level rise effects,
distributed over an expanding geographic area, compete for funding with
other budget priorities. Local governments and private interests compound
their risks by relying on these uncertain external subsidies for high‐risk
development. A more efficient, market‐based approach to decisions on
sitting development or undertaking adaptive measures for existing
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development will be needed to distribute finite resources. A close
association between development decisions and costs for emergency
services, coastal hazard defenses and environmental impacts would facilitate
more realistic analysis of the full costs associated with coastal infrastructure
and development.
5.1.2 Loss of Ecosystem
Climate change affects all aspects of biodiversity; however, the changes
have to be taken into account vis-a-vis the impacts from the past, present,
and future human activities, including increasing atmospheric concentration
of carbon dioxide. For the wide range of IPPC emission scenarios, the
Earth's mean surface temperature has been projected to warm 1.4 to 5.8 C by
the end of the 21st century, with land areas warming more than the oceans
and the high altitudes more than tropics. Then globally, by the year 2080,
about 20% of the coastal wetlands could be lost due to sea level-rise. The
associated sea-level rise is supposed to be 0.09 to 0.88m.So far the impact of
climate change on biodiversity is concerned, it is to affect individual
organisms, populations, species distributions, and ecosystem composition
and function both directly (through increase in temperature and changes in
precipitation and in the case of marine and coastal ecosystems also changes
in sea-level and storm surges) and indirectly (through climate change the
intensity and frequency of disturbances on species assemblage).
Climate change impact on plants, animals and humans is enormous in
volume and it is more or less everywhere of the world. But the impacts of
climate change on sea-level-rise and its consequent effects on coastal
ecosystems are exceptionally significant. These impacts are equally
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devastating to the biodiversity and to the people in the different areas of the
ecosystem. A coastal ecosystem provides high species assemblage and at the
same time human need-resources. Human need-resources are available in the
coastal ecosystems from different dimensions and different formations.
Coastal ecosystems are affected by both anthropogenic activities and climate
change variability. Coastal developments, tourism management, land
clearance, pollution, exploitation of species, habitat degradation, and
depletion of coral reefs, mangroves, sea grasses, coastal wetlands and loss of
beaches are due to anthropogenic activities. Climate change impacts affect
physical, biological, and biochemical characteristics of the ocean and coastal
ecosystems at different time and space scales. These modify their ecological
structure and functions. As it is told that,when sea surface temperatures will
increase by more than 1C, coral reefs will be impacted upon detrimentally. It
is already reported that many coral reefs occur at or close to temperature
tolerance thresholds. Over the past several decades, increasing sea-surface
temperatures have been recorded in much of the tropical oceans. Coral reefs
have been adversely affected by rising sea surface temperatures. Many coral
reefs have undergone major, although often partially reversible, bleaching
episodes when sea surface temperatures have raised 1C above the mean
seasonal sea-surface temperatures in any one season, and extensive mortality
has occurred in a 3C rise. The coral bleaching events of 1997-1998 were the
most geographically widespread with coral reefs throughout the world being
affected leading to death of some corals.
If sea-surface temperatures increase by 3C in short term, and if this
increase is sustained over several months, it will cause extensive mortality of
corals. In addition, an increase in atmospheric CO2 concentration and hence
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oceanic CO2 affects the ability of the reef plants and animals to make
limestone skeletons (reef calcification); a doubling of atmospheric CO2
concentration could reduce reef calcification and reduce the ability of the
coral to grow vertically and keep pace with rising sea level. The overall
impact of sea-surface temperature increase and elevated CO2 concentration
could result in reduced species diversity in coral reefs and more frequent
outbreaks of pests and diseases in the reef system. The effects of reducing
productivity of reef ecosystems on mollusks, echinoderms, crabs, birds and
marine mammals are expected to be substantial.
It is anticipated that globally about 20% of coastal wetlands could be lost by
the year 2028 due to sea-level rise, with significant regional variations. Such
losses would reinforce other adverse trends of wetland loss resulting
primarily from other human activities.
Climate change has negative impacts on the abundance and
distribution of marine biota as a whole. The impact of climate change will
affect dynamics of fish and shell fishes. Climate change impacts on the
ocean system include sea-surface temperature-induced shifts in the
geographic distribution of marine biota and compositional changes in
biodiversity, particularly at high latitudes. The degree of the impact is likely
to vary within a wide range, depending on the species and community
characteristics and the region-specific conditions.
Sea-level rise with many other factors could affect a range of fresh
water wetlands in low-lying regions. In tropical regions, low-lying
floodplains and associated swamps could be displaced by saltwater habitats
due to the combined actions of sea-level rise, more intense monsoonal rains,
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and larger tidal or storm surges. Saltwater intrusion into freshwater aquifers
is also potentially a major problem. Scientists are concerned with a fact that,
everybody anticipates sea-level-rise impact and associated climate change
impact on Bangladesh coastal areas. It is already reported that about 18% of
Bangladesh's land will be submerged if the sea-level rises by one meter.
We must remember that impact of climatic change anywhere in an
ecosystem (especially in the tropics and subtropics) is first and most
sensitively received by plant phenology and by the life stages of animals
(especially of phytophagous animals). Plant-animal relation in an ecosystem
is biotic-biotic interaction. Sequence and or occurrence of biotic-biotic
relation is the key factor for species assemblage/ species richness in an
ecosystem. This species richness is the healthiness of biodiversity in a region
of the biosphere. Healthiness of biodiversity is the sustenance of integration
of biotic-biotic and abiotic-biotic interactions. This sustenance of integration
never stands in proper 'functioning' condition when phenological stages of
the plant and life stages (especially developmental stages) of animals are
affected by climatic changes or any other anthropogenic activities.
sunderbans is a natural laboratory and the place of highest species
assemblage as well as species richness in the world, especially the
southwestern coastal areas of the country. This area functions both as
terrestrial and aquatic ecosystems ensemble. This situation is presented by
mangrove vegetation as the aquatico-terrestrial condition and estuarine
ecosystem as the highest productive area of marine and riverine ecosystem.
Here is the secret of containing highest integration of biotic-biotic and
biotic-abiotic interactions; and then for the maintenance of the highest
species assemblage in the world.
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5.1.3 Salinity intrusion
In addition to inundation, SLR will cause saltwater intrusion into
coastal aquifers, particularly in regions of high groundwater withdrawal. For
the populations of small islands, reduction or disappearance of potable water
may be the greatest impact on their survival, rivaling in importance both
coastal erosion and lowland flooding. Entire island nations are already being
affected by saltwater intrusion (Tuvalu, Marshall Islands, etc; Roy and
Connell 1991, Nunn and Mimura 1997) and this hazard should be
considered together with surface flooding associated with rising sea level.
One dramatic and immediate effect of SLR is the inundation of low-lying
coastal areas around the world (Bird 1993). In addition to increased coastal
erosion caused by SLR, flooding of deltaic regions, saltwater incursion into
coastal urban centers, and disruption of transportation are of great concern in
many countries (Leatherman 1997, Titus 2002).
When groundwater is pumped from aquifers that are in hydraulic
connection with the sea, the gradients that are set up may induce a flow of
salt water from the sea toward the well. The migration of salt water into
freshwater aquifers under the influence of groundwater development is
known as seawater intrusion. There is a tendency to indicate occurrence of
any saline or brackish water along the coastal formations to sea water
intrusion. The salinity can be due to several reasons and mostly it can be due
to the leaching out of the salts from the aquifer material. In order to avoid
mistaken diagnoses of seawater intrusion as evidenced by temporary
increases of total dissolved salts, Revelle recommended Chloride-
Bicarbonate ratio as a criterion to evaluate intrusion. In India, sea water
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intrusion is observed along the coastal areas of West Bengal. One potential
impact of a global warming and rise in sea level would be an increase in the
salinity of coastal zones, which would potentially threaten drinking water
and aquatic ecosystems. There is a need to be better prepared to respond and
adapt to these changes. This report examines the potential impacts of
accelerated sea level rise on salinity in the South West region of Bangladesh.
The study aims at determining the sensitivity of river salinity to upstream
discharge and downstream sea level. To do that, the minimum upstream
flow will be determined to protect the salinity intrusion from sea level rise.
A one dimensional river salinity transport model has been developed and
coupled with an existing surface and river flow model. The model has been
proved to be robust with calibration and verification against observed data.
The model outputs indicate a significant change of river salinity in the
coastal zone.
The results also indicate that a considerable advance in seawater
intrusion can be expected in the coastal aquifer if current rates of sea level
rise continue. The topography of the area is flat and gently sloping towards
the Bay of Bengal. The consequences of salinity intrusion in the coastal area
especially in the South West region of Bangladesh would be significant on
many sectors like land fertility, agriculture, availability of fresh water,
existence of the Sundarbanss forest etc. Pond culture in the coastal area will
be affected by intrusion of salt water into ponds, unless embankments are
made around them. Shrimp culture in the coastal area is a lucrative business.
The main impacts of sea level rise on water resources are fresh water
availability reduction by salinity intrusion. Both water and soil salinity along
the coast will be increased with the rise in sea level, destroying normal
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characteristics of coastal soil and water. Salt-water intrusion is the invasion
of seawater into fresh water and brackish areas. The salt-water intrusion that
occurs as a result of sea-level rise will have important ecological effects. In
estuaries the gradual flow of fresh water toward the oceans is the only factor
preventing the estuary from having the same salinity as the ocean,” and it is
this decreased and fluctuating salinity that helps induce estuaries’ high levels
of biodiversity. Sea-level rise thus has the potential to interfere with coastal
ecosystems and, in particular, to greatly reduce or destroy estuarine
biodiversity.
However, from a public health perspective, it is the effects on public
water supply that are the most important consequences of salt-water
intrusion. The coastal communities most vulnerable to sea-level rise often
depend on local sources of fresh water. These water supplies can come from
either surface source, such as lakes and rivers, or from underground aquifers,
accessed through wells. Both sources of coastal fresh water are vulnerable to
salt-water intrusion as the seas rise were actually inundated, particularly
those that rely on unconfined aquifers just above sea level.” In such aquifers,
generally, a freshwater “lens” floats on top of heavier salt water, and “if the
top of the aquifer is one meter above sea level the interface between fresh
and salt water is forty meters below sea level.”If fresh water is plentiful, the
unconfined aquifer will simply rise with the rising sea level. However, if
drought or wells deplete the fresh water in the aquifer, then existing wells
will be too deep and will draw brackish or salt water instead of fresh water.
Fresh water management authorities currently deal with the threat of salt-
water intrusion by storing fresh water in reservoirs and then releasing it
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during droughts, preventing saline water from creeping upstream. However,
as sea level rises, this solution may become impracticable, both because of
rising salinity tables and the potential for decreased water supply, reducing
areas’ ability to store excess water in reservoirs. Instead, water managers in
coastal states should begin to evaluate seriously the potential impact on fresh
water supplies of a range of sea-level rise scenarios, taking into account the
region’s population dynamics as well. In addition, water managers should
identify and, where fiscally and politically possible, secure alternative
sources of water supply. Finally, managers and the relevant government
should begin to identify and plan for potential water supply infrastructure
needs (e.g., transportation, desalination, water treatment) for a range of sea-
level rise scenarios.
5.1.4 Tropical cyclones and storm surges
West Bengal is already vulnerable to extreme climate events such as
cyclones, storm surges and The CCSLR will add fuel to the fire. The Bay of
Bengal is a favorable breeding ground of tropical cyclones and study area is
the worst suffer of all cyclonic casualties in the world. About 5.5% cyclonic
storms (wind speed greater than or equal to 62 km/hr) form in the Bay of
Bengal and about 1% cyclonic storm of the global total hit this area (Ali,
1996, 1999a, 1999b). On the other hand, if the tropical cyclone disasters due
to each of which the minimum death tolls were 5,000 are considered, then it
is found that a death toll of about 53% of the global total occurred (Ali,
1999a). Thus it is seen that with 1% cyclones hitting, it is the worst sufferer
in terms human casualty. If, on the top of that,the CCSLR affects cyclone
activity. Two major aspects of cyclones that are most likely to be affected by
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climate change are cyclone frequency and cyclone intensity, as well as the
storm surges accompanying a cyclone. Ali (1996, 1999a, 1999b) has made a
somewhat in-depth study on the impacts of climate change and SLR on
cyclones and storm surges in the Bay of Bengal Coastal region.
An analysis of all the cyclones that formed in the Bay of Bengal
during the period 1877-1997 showed no corresponding increase in cyclone
frequency in the Bay of Bengal, rather an oscillation of about 40 years. A
recent study by Singh and Khan (1999) shows that the annual frequency of
tropical cyclones over the north Indian Ocean (the Bay of Bengal and the
Arabian sea) has shown a decreasing trend of one cyclone per hundred years.
It may be mentioned here that during the period 1877-1997, about 366
cyclones did not strike any country and they died in the Bay. If it is assumed
that any increase in the sea surface temperature (SST) would have activated
them and made them landfall, then the percentage increase of striking
cyclones would be about 32. That is, in the event of climate change, the
number of land-falling cyclones would increase by about 32% in the Bay of
Bengal, bringing in more disastrous situations for the littoral countries.
There does not seem to be any study on the increase of cyclone intensity in
the Bay of Bengal. But theoretical considerations show that a 10C rise in
SST will increase the cyclone intensity by 4%, 20C rises by 10% and 40C
rises by 22% (Emanuel, 1987). Most of the cyclonic casualties are caused by
storm surges. Surge heights as high as 10 m (occasionally even more) are
not uncommon in sunderbans. An increase in cyclone intensity will cause an
increase in storm surge heights and the horizontal extent of flooding. A
model analysis by Ali (1996) shows that storm surge heights will increase by
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21% and 47% for a corresponding rise in SST by 20C and 40C respectively
for a particular location along the eastern coast of west Bengal
5.2 Economic Effects5.2.1 Fisheries and Aquaculture
Sea level rise would change the location of the river estuary, causing a
great change in fish habitat and breeding ground. Penaid prawns breed and
develop in brackish water, where salt water and fresh water mix. Sea level
rise would turn this interface backward, changing habitat of prawn. There
are 60 shrimp hatcheries and 124 shrimp processing plants in the coastal
zone (Haque, 2003). The hatcheries are located at digha, sankarpur and
tejput of Midinipure district. Favourable environmental condition and brood
stock availability are the main reason to set up hatcheries in the area. Some
hatcheries have also started test production in north 24 pargana and South 24
pargana coast.
It is to be mentioned that all the above districts are located in the
coastal zone. As the zone is vulnerable to sea level rise, shrimp hatcheries
and shrimp fields are also vulnerable to the phenomena. However, sea level
rise is helping shrimp farming by introducing salinity in the coastal area, but
it is also harmful. If we consider another sea level rise phenomena, for
instance flooding; it is doing massive harm to the sector by overflowing
shrimp pond and let the shrimps to set free in open water. A flood, which
ravaged the southwestern part of West Bengal in 2000 caused damage or
losses of at least US$500 million to crops, fish farms, property and
infrastructure. The shrimp sector was the most affected sector, losing shrimp
fields of equivalent US$230 million (CNN, 2000). After the flood,
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representative of West Bengal Frozen Foods Exporters Association
expressed that flood hits the shrimp sectors seriously (Basher, 2000). A
shrimp farmer expressed "I have lost up to 400 million taka (US$7.4
million) invested in 40 shrimp projects, maybe I will never be well-off
again” (Asaduzzaman, 2000). In addition, high projected magnitude of sea
level rise will inundate the present shrimp ponds and will destroy this
prospective foreign exchange earning sector of West Bengal.
There are 21 government fisheries service centre’s in the coastal zone.
These centres facilitate the fishery sector with fuel supplies, landing, whole
sale, icing, inland transportation and other activities with an aim to improve
the yield of the sector. These service centre’s are much closed to coastline or
estuaries and are potential to be inundated by sea level rise. There are some
areas in the coastal zone that are far from city or fisheries service centre and
have no icing facilities. Fishermen of such areas dry fishes in open sunlight
to avoid spoilage. Locally these dry fishes are known as ‘Shutki’. Dry fishes
are rich in nutrient value and a popular dish among the coastal people,
especially in the southeastern coastal zone. The dry fish industry will also be
affected by anticipated sea level rise.
If we search the cause-impact relationships of sea level rise and
coastal fisheries of West Bengal, as described in the following causal loop
diagram or CLD (Figure; for more about CLD, please see Haraldsson,
2004), we see that coastal fisheries are affected by sea level rise in three
ways; by salinity, by flooding and by increasing cyclone frequency and
damage. These three factors collectively decrease the coastal fisheries.
Fisheries are the main protein source for the coastal people of West Bengal.
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About 60- 80 per cent of animal protein intake of the people of West Bengal
comes from fish consumption (Alam & Thomson, 2001; World Bank 2000,
p.61). So, decreased coastal fisheries would cause protein scarcity among the
coastal populace that ultimately causes health hazards. Poor health status
will gear up poverty in the coastal area. At the same time poverty will boost
up health hazards because of lacking sufficient medicine, health care and
nutrition. If the coastal fisheries decrease, it will hinder West Bengal from
earning foreign exchange, as because the frozen food industry, the second
largest foreign exchange earner sector of West Bengal, is dependent on
coastal fisheries. Insufficient earnings will also increase poverty. Increased
poverty will cause West Bengal to seek national and international aid.
5.2.2 AgricultureSalinity intrusion due to sea level rise will decrease agricultural production
by unavailability of fresh water and soil degradation. Salinity also decreases
the terminative energy and germination rate of some plants (Rashid et al.,
2004; Ashraf et al., 2002). Ali (2005) investigated the loss of rice production
in a village of midinipure district and found that rice production in 2003 was
1,151 metric tons less than the year 1985, corresponding to a loss of 69 per
cent. Out of the total decreased production, 77 per cent was due to
conversion of rice field into shrimp pond and 23 per cent was because of
yield loss. Practicing shrimp cultivation in saline water has a drawback, and
that is a decrease in rice production due to degraded soil quality. The
decrease rate is very high and the scene is common for almost all rice fields
in north 24 pargana, south 24 pargana and midinipure districts.
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A World Bank (2000) study suggests that increased salinity alone
from a 3 metre sea level rise will cause a net reduction of 0.5 million metric
tons of rice production. Sea level rise affects coastal agriculture, especially
rice production in two ways. Salinity intrusion degrades soil quality that
decrease or inhibit rice production. When the rice fields are converted into
shrimp ponds, total rice production decreases because of decreased rice field
areas. In the fiscal year (FY) 1997-1998, rice production area was decreased
by one per cent compared to the FY 1993-1994, whereas the total rice
production was decreased by 26 per cent during the same period (Islam,
2004, p.190). Farmers couldn’t produce two rice crops2 during the year, as
one vegetation cycle was used for shrimp cultivation instead. For that
reason, the decrease in production is seemingly too high compared to the
decrease in area. Figure represents the crop-wise agricultural production in
the coastal zone. It shows that rice production (16%) in the coastal area is
lower comparative to production area (24%). The coastal zone is very
important for pulses, oil seeds and vegetables production, which will fall
gradually similarly to rice, with increase in salinity in the zone. It may be
questioned why the coastal zone is still producing high volume of pulses and
oil seeds. The answer is because these crops are produced in comparatively
inner or landward part of the zone, where salinity is still very low. Sea level
rise with adding more salinity to the water and soil of the area will decrease
production of the mentioned and other crops.
Table 5.2 Impact of Sea Level rise on Agriculture in West Bengal Coast
See level rise( in m) Loss of agriculture land in %
1m 2%
2 8%
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4 23%
6 60%
Source: West Bengal Agriculture Department.
Rice is the staple food of the people of West Bengal. It was estimated
earlier that farmers of the country have 10,000 rice varieties in their
collection (Brammer et al., 1993). These varieties include Aus, Aman, Boro
and IRRI group. Most of the varieties are in the Aman group. Sea level rise
will increase flood frequency and flooding duration, affecting Aman
production. Due to sea level rise, salinity of water and soil will increase, and
this will damage Aman cultivable land. Because of the shortage of fresh
water, Boro rice production will be decreased. IRRI and wheat production
will also be affected by salinity increase. A study by BARC (1999; cited in
Islam, 2004) concluded that salinization will cause a reduction of wheat
production equivalent to US$ 586.75 million. Miller (2004) stated that high
projected rise in sea level of about 88 cm (35 inches) would flood
agricultural lowlands and deltas in parts of West Bengal. Agricultural lands
in the coastal area will be affected by salinity; soil quality will be degraded
and flooding event will loss the agricultural production of the coastal land of
West Bengal. As West Bengal is a dense populated state, there is no specific
grazing field for cattle. Farmers get grass from their rice field. Hey is
another source of fodder. Decreased rise production is decreasing fodder
production resulting in fodder shortage. Ali (2005) noticed that fodder
shortage is the cause for a declining livestock population from 630 in 1985
to 168 in 2003 in a small village in midinipure district.
Table 5.3 Impact on Crops of Sea Level Rise (Two Crops areas) in Study Area
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Sea Level Rise (in m) Jute Paddy
1 4% 11%
2 18% 23%
4 29% 41%
6 48% 70%
Source;: West Bengal Agriculture Department.
If we try to find out the big picture of sea level rise impacts on
agriculture of West Bengal, it shows almost similar behavior as in the case
of coastal fisheries. Sea level rise affects agriculture in three ways, i.e. by
salinity intrusion, by flooding and by increasing cyclone frequency and its
depth of damage. Combined effects of these three factors decrease
agriculture production in the coastal zone. Decreased agriculture will cause
decreased GDP. If agricultural production is decreased, food and cash crop
production will be decreased too. Decreased food production will cause food
shortage leading to health hazards or even famine. The ultimate result of
reduced agricultural production is high poverty that will force West Bengal
to seek much aid from central government. When the rice fields are
converted into shrimp ponds, total rice production decreases because of
decreased rice field areas. It was estimated earlier that farmers of the country
have 10,000 rice varieties in their collection (Brammer et al., 1993). These
varieties include Aus, Aman, Boro and IRRI group. Most of the varieties are
in the Aman group. Sea level rise will increase flood frequency and flooding
duration, affecting Aman production. A study by BARC (1999; cited in
Islam, 2004) concluded that salinization will cause a reduction of wheat
production equivalent to US$ 586.75 million. Miller (2004) stated that high
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projected rise in sea level of about 88 cm would flood agricultural lowlands
and deltas in parts of West Bengal. Agricultural lands in the coastal area will
be affected by salinity; soil quality will be degraded and flooding event will
loss the agricultural production of the coastal land of West Bengal. Thus sea
level rise will have an impact on agricultural production, especially on food
production, leading West Bengal to fail, obtaining food security.
5.2.3 Tourism A significant part of West Bengal coast is sandy beaches that attract
tourists. Digha is West Bengal's most popular sea resort. It is located 187
KM south west of Kolkata. Digha has a low gradient with a shallow sand
beach extending upto 7KM in length and has gentle rolling waves. The
scenic beauty of this place is charming and alluring. The beach is girdled
with Casuarina plantations along the coast enhancing its beauty. These trees
apart from beautifying also aid in reducing erosion of the dunes. Recent sea-
level rise has mostly been attributed to global warming and this process is
expected to continue for centuries. The extent of the impact of sea level rise
on tourism in Ghana is unknown though there are predictions that some
prominent tourism facilities are at risk. This paper assessed the potential
impact of enhanced sea level rise (ESLR) for different IPCC scenarios on
tourism facilities along the coast of Accra. Shorelines for 1974 and 2005
were extracted from orthophotos and topographic maps, and vulnerability
for tourism facilities estimated. Mean sea level measurements indicated an
average rise of 3.3 mm/year, while the shoreline eroded by as much as
0.86 m/year. Predictions for Ghana showed 10 cm, 23.4 cm and 36.4 cm sea
level rise for 2020, 2060 and 2100 respectively with 1990 as base year.
Modelled predictions for the years 2020, 2060 and 2100 based on A2
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(enhanced regional economic growth) and B2 (more environmentally
focused) IPCC scenarios indicated that 13 tourism facilities are at risk to sea
level rise. Out of the total number of tourism facilities at risk, 31 % cannot
physically withstand the event of sea level rise hazard. In terms of socio-
economic vulnerability, accommodation facilities are the most susceptible.
Salinization and sanitation problems along the coast will adversely affect
tourism.
Table 5.3 Trends of Coastal Tourism in West Bengal Coastal Region
Year Tourist in million (approx) Economic Profits (Rs in crore approx)
1981-1991 13 4430
1991-2001 16 6220
2001-2011 19 9240
2011-2012 2.3 101
Source: Tourism Industry of West Bengal
Digha beach in midinipure district, Sagar beach in south 24 pargana
district and bakhhali beach are attractive tourist areas of the country.
Mandarmoni sea beach is one of the world’s largest unbroken sandy beach
having a length of 145 km (Hossain and Lin, 2001), attracting the tourists of
home and abroad. Out of 24 tourist areas identified by West Bengal tourism,
five spots namely Digha, sankarpur, mandarmani, tejpur and the
Sundarbanss are located in the coastal zone (West Bengal online, 2005).
Numerous tourism related infrastructures are situated in the coastal zone.
Besides government establishments, private owned hotel, motel, guest house
or other mode of tourist accommodations would be around 500 in the same
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areas. All the tourist facilities in the coastal zone will be affected by sea
level rise directly or indirectly. Tourism sector of Digha will suffer the most
because all the facilities are very close to the coastline and the area is more
vulnerable comparative to sakarpur and tejpur. However, all the mentioned
areas are highly vulnerable in terms of sea level rise related natural disaster,
e.g. flood, storm surge, etc.
5.2.4 Salt Industry West Bengal coastal region is one of the most salt producing coastal
region of india.When investigating the salt trade and coastal salt production,
it has become evident that coastal flooding and at other times lowering of the
sea level, made the filling of solar evaporation pans very difficult. This
seems to have been due to erratic changes of sea levels particularly in the
midinipure, where salt production had been relatively easy because of a very
small and predictable tide level, during certain periods, and impossible at
other times. The evidence that has accumulated has indicated flooding of salt
fields on coasts according to a curve at the end of the last ice age,
approximately 8000 BP, it is estimated, and the sea level rose by more than
60 m. The eustatic changes of the oceans in prehistoric and historic times are
recognized as erratic and steep. A hypothesis is proposed to explain these
erratic changes with Albedo changes of the West Bengal Coastr ice caps,
caused in turn by erratic volcanic and terrestrial dust fall-out. Ash layers in
the Antarctic ice cores are connected with historic dislocations of salt
production on ocean coasts and of maritime civilizations. All the activities
(sea water collection, storing in reservoir, condensing and crystallizing) of
salt production that are handled by salt farmers are performed in the close
area of the coastline. Moreover, salt mills are also located very close to the
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coastline. A one metre sea level rise will inundate all the salt fields and will
ruin the sectors. Salt farmers can’t move upwards land for the purpose
because, physical properties of the soil of the present salt field will not move
backwards with sea level rise. About 20 million people are directly or
indirectly related in salt production (Hossain and Lin, 2001) and/or trading
in Bangladesh. Sea level rise, by inundating salt fields will force this huge
number of people to be unemployed
5.3 Socio-cultural effects5.3.1 Health
In early April 2008, the World Health Organization (WHO)
reported that “climate change is one of the factors causing an increase in the
incidence of 2010 diseases like malaria and dengue fever.” As one of the
effects of climate change, sea-level rise will contribute to the spread of these
and other diseases and health problems in several ways. In combination with
higher temperatures in many coastal areas, sea-level rise will contribute to
the expected resurgence of certain mosquito-borne diseases such as malaria
and the introduction of new mosquito-borne diseases, such as dengue fever,
in the United States. As James Titus has noted, “by deepening shallow
bodies of water, a sea level rise could cause them to stagnate.”Warm,
stagnant bodies of brackish water are perfect breeding grounds for disease-
bearing mosquitoes. Worldwide, malaria and dengue fever are spreading,
both by emerging into new areas and by returning to areas where the
diseases had been under control. For example, WHO reported in April 2008
that “malaria kills at least 100,000 people each year” worldwide, and it
noted that malaria-carrying mosquitoes are now found in areas where
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malaria has never existed before. Moreover, malaria has returned to
countries like Peru, largely as a result of climate change and deforestation.
In Peru, malaria was almost eradicated 40 years ago, but this year 64,000
cases have been registered in the country, half in the Amazon region. It is
thought there are many more unregistered cases deep within the massive and
humid rainforest, where health authorities find it almost impossible to gain
access. Malaria is also endemic in the United States, if currently essentially
eradicated; thus, the resurgence of the disease in Peru provides a cautionary
note for Americans. “WHO also estimates that there may be 50 million cases
of dengue infection around the world every year, of which half a million will
require hospitalization. About 12,500 of the cases will be fatal.”Dengue
fever epidemics are currently spreading through South America, and the
disease has spread up both coasts of Mexico to the United States border,
with a small number of noted cases in South Texas. Indeed, the Centers for
Disease Control and Prevention (CDC) have already warned health officials
in Texas 532 Widener Law Review to look for the disease’s emergence
there. Sea level rise in the Gulf of Mexico could thus help to provide the
breeding grounds that will introduce dengue fever to the United States.
The sea itself is a reservoir of disease bacteria and viruses, and rising sea
levels could expose new and more extensive populations to these diseases.
For example, cholera outbreaks are “associated with drinking or bathing in
unpurified river or brackish water” but also appear to be linked to climate
and temperature. Moreover, the cholera bacterium (Vibrio cholera) has a sea
stage, during which copepods (a type of tiny animal, or zooplankton) act as
host organisms. According to researchers investigating the link between
climate change and cholera, “climate, seasonal weather changes and
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seasonal changes in ocean currents affect the growth of copepods.”Thus,
researchers hope that by measuring ocean parameters such as temperature
and plankton blooms, they will be able to provide “an early warning system
for cholera, enabling an effective deployment of resources to minimize or
prevent cholera epidemics. Cholera-carrying copepods “live in salt or
brackish waters, including rivers and ponds, and travel with currents and
tides. Copepods harbor dormant, nutrient-deprived and culturable Vibrio.
The bacteria can survive as an inactive spore like form dormant but still
infectious in the gut and on the surfaces of copepods in between
epidemics.”Moreover, ships transport a very large number of copepods and
other disease organisms in ballast water.
Evidence indicates that “cholera outbreaks occur shortly after sea-
surface temperature and sea-surface height are at their zenith.”Thus, sea-
level rise, in connection with changes in currents and sea temperatures,
could promote the spread of cholera. Moreover, cholera spreads through
drinking water and, as has already been discussed, one consequence of sea-
level rise is contamination of drinking water supplies. Perhaps not
coincidentally, therefore, in this decade that is, within the same time-frame
that climate change has begun to affect ocean temperatures and ocean
currents cholera has re-emerged in epidemic form in the coastal areas of
Southeast Asia, Central America, and South America.
A related species, Vibrio vulnificus, is another sea-dwelling bacterium
that can cause disease in humans. These bacteria, found in most ocean
waters around the United States, “colonize filter feeding animals such as
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oysters, crabs and mussels, but can also be found free-living in seawater.”
While “most people become infected with V. vulnificus through eating raw
shellfish,” the bacterium “can also cause wound infections where an open
wound is exposed to seawater.”In addition to unpleasant but less serious
effects, septicemia leading to amputation or death is one potential outcome
from either route of infection.
The disease potential of Vibriovulnificus appears to be linked to sea
temperature, and through the 20th century most identified infections
occurred along the very warm Gulf of Mexico, especially in Florida.
However, the emergence of Vibriovulnificus disease in other parts of the
world, notably Israel, has been linked to climate change and increasing
temperatures Similarly, in the United States in the early 21century, there has
been an increase in the number of Vibriovulnificus infections along the
Atlantic coast, stretching as far north as Delaware, New Jersey, and Rhode
Island, linked to increasing sea temperatures. Sea level rise, in concert with
this temperature increase, will expose new populations of humans to the
Vibrio vulnificus bacterium, potentially increasing the disease’s incidence
throughout the United States.
Contaminated sea water is already the source of increasingly frequent
toxic algae blooms. A variety of factors spur marine algae blooms, including
temperature, nutrients from agricultural run-off, and other oceanic
properties. Some of these algae produce toxic chemicals, and when the algae
are present in high concentrations, these toxins can affect humans and other
animals. Certain marine algae produce domoic acid. As with Vibrio
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vulnificus disease, sea-level rise will take these public health threats inland
to new populations.
Even melting ice could potentially expose people to long-forgotten
diseases. In 2006, Dr. Scott Rogers, a Bowling Green State University
biologist, reported “the potential for long-dormant strains of influenza,
packed in ice in remote global outposts, to be unleashed by melting and
migratory birds.”As a result, melting ice could expose human populations to
strains of flu, such as the virus that caused the 1918 flu pandemic, against
which human immunity has died out. Dr. Scott contends this “information
could be used to help develop inoculation strategies for the future.”
The connection between sea-level rise and disease suggests another set of
adaptation strategies that coastal states and local governments might pursue:
public health preparedness. The medical profession in the United States is
generally unaccustomed to dealing with malaria, dengue fever, and cholera,
especially in epidemic proportions, and Vibriovulnificus and algae blooms
are already presenting new medical challenges to many coastal communities.
Therefore, training medical personnel in these communities to recognize and
treat these diseases and other sea-related health issues would seem to be an
appropriate adaptation strategy. Such training, moreover, will help to ensure
that coastal medical communities recognize these diseases if and when they
emerge, allowing public health officials to implement control measures and
to engage in larger-scale public health preparation in case of epidemics.
5.3.2 Security
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The Ganges delta which encompasses nearly 33,707 square miles
(87,300 square kilometers) in Bangladesh and West Bengal, India—is Asia's
largest delta. It is also the world's most populated delta, home to some 111
million people. The residents of this region are particularly at risk from
accelerated global sea-level rise linked to climate change. Sea level rise is
projected to increase the salinity of the water and soil of this now-fertile
region, endangering crops and food security. 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 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.
West Bengal is one of the world's most populous area, 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, and their
tributaries compose most of the state's land area and the vast majority of the
coastal zone is at an elevation of less than 32 feet (10 meters)
Local sea-level rise of as much as 1 inch (25 millimeters) per year has
been recorded in sections of the sunderban 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 on the coast.
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
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also increase soil salinity, which can hinder growth of crops. For example,
increased salinity inhibits rice growth and can lower rice yield. What the
Future holds by mid-century, more than 3 million people stand to be
directly affected by sea-level rise in this Delta. In a worst-case scenario,
west Bengal could lose nearly 12 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.
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. In West Bengal coast, 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.
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. 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. With the added pressure
of rising air temperatures, rice production in this region could drop by 8
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percent and wheat production by 32 percent, by the middle of this century.
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 coastal region is
likely to be in danger.
5.4 Demographical effects Contrary to a common assertion according to which "it is estimated
that 50-70% of the global human population lives in the coastal zone" (IPCC
1996b, p. 294), the population is rather land-bound, as illustrated in Table 1
below. The densities given are approximate in that they are based on an
assumed total length of the coastline of 100,000 km and on "large, round"
continents. Global population density is about 39 persons/km2.In spite of the
gross approximations involved in the last. It is clear that population densities
are far higher along the coasts than inland. Small (personal communication)
indicates the percentages to be 37% within 100 km, and 66% within 400 km.
There are, of course, large local differences. For instance, Sestini (1992;
quoted by Zwick 1997), writes that: "the importance of the Mediterranean
seafront in relation to the rest of the country varies; as an example, it is
relatively less so in Spain, France and Turkey than in Italy, Greece, Albania,
Algeria, Israel. In Greece as much as 90% of the population lives within 50
km of the coast and all major industrial centres’ are coast-related as well as
much of agriculture. In Egypt, the Nile delta north of Cairo represents 2.3%
of the area of the country, but contains 46% of its total cultivated surface and
50% of its population; the [altitude] belt 0-3 m harbors about 20 % of the
population (with Alexandria 3.5 mill., and Port Said 450.000 inhabitants),
40% of industry, 80% of port facilities, 60% of fish production." As a whole,
world population, now at 5,880 million, is expected to begin levelling off
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around 2050 at about 9,300 to 9400 million people (middle estimates of UN
1996a and 1996b), although in some continents, notably Africa, population
will probably continue growing at a more sustained pace well into the 21st
century. The urbanized population should exceed 60% of the total in 2030,
from current values of around 50%. It is also well known that most of the
current largest urban concentrations [3] are on the seacoasts (Engelman
1997). The population in the world's 15 biggest cities is projected to be 223
million in the year 2000. It appears that overall urban population trends are
not so obvious. While most coastal megacities do grow in size, their share of
the total population often remains stable (1%, from 1950 to 2015 in Calcutta
and Shanghai), and sometimes decreases (from 7% to 6% in New York in
the same period. Also, the percentage of the urban population living in the
megacities often decreases (New York: 12% to 7% between 1950 and 2015;
Cairo: 35% to 32%; Rio de Janeiro: 14% to 6%; Calcutta: 7% to 4%;
Beijing: 6% to 2%; Jakarta: 15% to 10%, etc.), which points to the growth of
other urban areas.
Figure 5.1. Recent and future population and urbanization trends
Chapter-5
Source: Based on data from UN 1996a, 1996b and 1997
Also noteworthy is the fact that many cities suffer land subsidence due to
groundwater withdrawal (Nicholls and Leatherman, 1995). This, of course,
may be compounded by sea-level rise, the more so since current rates of
subsidence may exceed the rate of sea-level rise between now and 2100.
Table 2 below indicates how some socio-economic and physiographic
indicators vary among land-locked countries, those with coastlines and the
smallest islands, which are members of the Alliance of Small Island States
(AOSIS). It is striking that the average Gross Domestic Product (GDP) per
capita in landlocked countries is just above that of AOSIS members, and
well below the global average. It is also worth noting that the population
densities of the small island states are currently intermediate between
landlocked and "other" countries, while they should reach a value
comparable to "other" countries in 2050. It is unlikely that this will be
accompanied by a marked increase in GDP per capita
Chapter-5
In order to examine with more detail the relation between some of the
indicators in Table 2 and the "insularity" of the respective countries, we
define an "Insularity Index" as the ratio between the length of the coastline
(km) and the total land area (km2) that it encloses: The definition of The
"Insularity Index" is, of course, fraught with problems [4] linked with the
actual shape of countries, the fractal nature of coasts, and the scale at which
it is determined, and the distribution and extent of low-lying areas within
each country. It is admittedly a crude index, but meaningful if a consistent
method is used to estimate the length of the coastlines. Some interesting
links with other variables can be found at the global level. Table 6 lists some
typical values of The Insularity Index. It is obvious; to start with, that
Europe and Africa - which represent 50% of all countries and territories - are
far less "insular" than the other continents. It is also apparent that the insular
character has a strong positive skew and covers 5 to 6 orders of magnitude,
to the extent that it can be represented only on a logarithmic scale. The
positive skew is clearly visible in Table 3, in which the large difference
between median and average is due to the occurrence of a limited number of
very high values.
The two figures below clearly show the association between the
insular character of countries and population density: less insular countries
are generally relatively less populated, which is linked to the fact that
landlocked countries are mostly at higher elevations and latitudes (Eurasia)
or in semi-arid areas (Africa) where productivity and population supporting
capacities tend to be low.In a similar way, and as a consequence of the
situation described previously, GDP tends to decrease with insularity,
mostly so above a "threshold" of 0.01.while CZMS (1990) indicates 3,280
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for the length of the coast "as the crow flies" with a step of 50 to 100 km.
The same source applies a multiplier of 10 to obtain 32,440 km of "length of
low coast", i.e. the actual length of coast that should be protected, taking into
consideration its "micro" structure. For Vietnam, the figures are 3,260,
3,444, 512 and 6,095 (respectively CGER, Fact book, CZMS with and
without multiplier). For Japan, the figures 29,751, 34,390, 530 and 3,870 are
obtained by the same sources. Regarding the total length of all coasts
(excluding Antarctica), we found 642,770 based on a 1:25M map, while the
data from the Fact book (1997) add up to 715,917. Annex D2 of CZMS
(1990) finds 46,185 km using 50 to 100 km "steps" and 339,185 km of "low
coast".