Rising Seas Threaten Cities, Erode Beaches and
Drown Wetlands in Key Developing Countries
("Potential Impacts of Accelerated Sea-Level Rise on Developing
Countries," is the subject of the Spring 1995 Journal of Coastal
Research Special Issue No. 14. To alert our readers to the
important results of this 5-year study, we have devoted an
entire issue of Climate Alert to short summaries of some of
the articles. - Ed.)
Megacities are growing on the coastlines of the developing world,
high-rise resort hotels are lining the beaches, wetlands are being
filled for development or converted to agriculture, deltas are
subsiding as groundwater is withdrawn and dams withhold sediment.
Much of this activity is taking place with little regard for the
risks of sea level rise and climate change. A five-year study
of ten developing countries, under the leadership of two scholars
in the US and the UK, with help from many in developing countries,
delineates the threats to the coasts - and by implication to the
coasts of the rest of the world - and suggests possible responses.
The sea level is already rising; over the last century it has
been estimated to increase about 1.8 mm (approximately 4/100 of
an inch) per year for a total of 0.18 m (nearly 8 inches). Global
warming could accelerate this trend: the ocean expands as it warms,
and the warming melts mountain glaciers. A further increase of
0.5 m (about 20 inches) is likely and 1 m is possible by 2100
according to a 1992 accelerated sea level rise scenario by the
Intergovernmental Panel on Climate Change.
Stephen Leatherman at the University of Maryland and Robert Nicholls
now at the University of Middlesex cite other key factors which
darken the picture:
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Half of the world's rapidly-growing population and 13 of
the 20 largest cities are in the coastal zone.
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Existing coastal hazards are not well understood.
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Coastal development is proceeding very rapidly, with little
regard even for present threats.
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The financial cost of a 1-meter rise for many developing
countries would be significant.
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Serious global loss of wetlands is almost certain under accelerated
sea level rise, an illustration of the limits to the ability
of humans to counter projected damage.
Of the 10 countries studied, Bangladesh, Senegal, Nigeria and
Egypt appear least able to cope with rising seas, because of large
and expanding coastal populations, limited experience with adaptation
techniques, low-lying areas submerged at high tide, and waves
eroding deposited sediment. China, Bangladesh and Egypt have the
largest populations living on vulnerable deltas. The tourist industry
would suffer most in Senegal and Uruguay because of the high cost
of beach nourishment. Brazil, Argentina, Venezuela and Hong Kong
were others among the 10 countries investigated. While there are
other effects of sea level rise: the intrusion of salt water into
aquifers, a rise in water tables, and increased flooding and storm
damage, only land loss due to inundation and erosion were considered
in this study.
Part of the U.S. Environmental Protection Agency International
Project, the study sought to determine the impacts and possible
responses to coastal land loss, through three phases:
1) National overviews based on existing literature and available
data
2) Case studies of existing areas based on new data
3) National assessments using an aerial videotape process to
determine the coastal resources at risk and the cost of protection.
A new reconnaissance approach, Aerial Videotape-Assisted Analysis
(AVVA) was developed because of a lack of basic data on the coastal
zones of most developing countries. (See Box on page 1.)
Three options are laid out as alternatives for treating the coasts:
1) No protection. The existing protection is ignored
and the threatened coastal zone abandoned.
2) Important areas protection. Medium to high development
areas are protected with beach nourishment (tourist areas) or
seawalls, and harbors are upgraded.
3) Total protection. Coastal areas with a population
of more than 10 people per square kilometer require action.
Coastal wetlands are always considered lost as no response action
assists in their preservation.
A synthesis of the results of the research revealed that:
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Bangladesh, Egypt and China would lose prime agricultural
land and parts of urban areas, Nigeria urban areas and oil
production facilities, and all of them would lose wetlands.
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More than 94 million are at risk in the four countries, mostly
in delta settlements, and there is a potential displacement
of millions from their homes. (Because it is uncertain what
responses will be - some people may be forced to leave
and some may choose to leave - and because protection
is both feasible and likely, neither the term "environmental
refugee" nor "environmental migrant" is used to describe these
populations.
The populated deltas, particularly in South and East Asia, suffer
iimpacts exacerbated by land subsidence or sediment starvation
by upstream dams:
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In the Nile Delta, 12-15 percent of the agricultural
land and 6 million people are at risk
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In the Ganges-Brahmaputra Delta of Bangladesh, 16
percent of the land used for national rise production and
13 million people are at risk
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In the 4 major coastal Deltaic plains of China, more
than 100,000 km2 of agricultural land and 72 million people
are subject to coastal flooding and land loss
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In the 5 Deltaic plains of India, 21,000 km2 and 21
million people are at risk
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In the Niger Delta, more than 15,000 km2 will be inundated
or eroded, including mangrove swamps and petroleum production
facilities
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In the Orinoco Delta of Venezuela, 5,000 km2 of wetlands
are threatened but they contain relatively few people.
High rates of relative sea level rise, reduced sediment, salt
water intrusion, dreding and filling for development, reclamation
and cutting of mangroves have diminished the wetlands in most
countries studied:
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In China, wetlands have been reclained for agriculture
and aquaculture.
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The only hope for long-term survival of extensive areas in
Malaysia, Bangladesh, and India, is placement
in national reserves.
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Loss of Nile waters, sediment, and reclamation are leading
to declining wetlands in Egypt.
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Mangroves in Senegal and Nigeria are threatened
by salinizatio andreclamation for rice paddies and industry.
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Only in rural areas of South America is the danger
to wetlands more limited.
The protection of cities is a major cost imposed by sea level
rise. In Shanghai and Tianjin, significant areas already lie beneath
existing high tides and are protected by extensive systems of
dikes and drainage to prevent flooding and complete inundation.
Subsidence because of ground water withdrawal is a major problem
in many coastal cities. Because of the high value of these areas,
they are most likely t o opt for some form of protection.
Although a comprehensive evaluation of the economic consequences
of sea level rise was beyond the scope of this study, an inventory
of the market value of land and buildings for the AVVA studies
showed substantial assets at risk.
While in most cases the protection options do not reduce land
loss significantly, they are an important factor in lowering value
loss. In some countries - e.g. Nigeria - even with Important Areas
Protection, over one million people would be displaced.
The synthesis of these studies reveals that accelerated sea level
rise would have serious impacts on the developing world. The vulnerable
population will grow to 137 million by 2020 and 165 million by
2050. (Even these figures understate the case because coastal
populations are growing faster than average.) The largest cities
will still be in Asia but Africa will see some of the fastest
growth, with Lagos, e.g., reaching 21 million by 2010, the world's
fifth largest city. No fundamentally new coastal problems will
be created but existing ones will obviously be much exacerbated
unless precautions are taken to minimize vulnerability.
The world's coastal zones are being developed at an unprecedented
rate, most of it with little regard to land loss and storm flooding,
in addition to the risks of accelerated sea level rise . Integrated
Coastal Zone Management could do much to decrease sea level rise
vulnerability.
If climate change is considered in today's decisions, it will
maintain flexibility for future generations. The world's coastal
zones will deviate with or without climate change. It is hoped
these alterations will occur, say the authors, within a framework
that "can cope with climate change and maintain the value of the
coastal zone to all mankind."
(To contact study editors by phone: S.P.Leatherman (USA), 301/405-4059
R.J. Nicholls (UK), 0181-362-5569)
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