LONDON (AP) -- For the first time, a scientific study has identified the world's low-lying coastal areas that are vulnerable to global warming and sea-level rise, and urged major cities from New York to Tokyo to wake up to the risk of being swamped by flooding and intense storms if nothing is done.
In all, 634 million people live within such areas -- defined as less than 10 meters (33 feet) above sea level -- and that number is growing, said the study released Wednesday.
Of the more than 180 countries with populations in the low-elevation coastal zone, about 70 percent have urban areas of more than 5 million people that extend into it, including Tokyo; New York; Mumbai, India; Shanghai, China; Jakarta, Indonesia; and Dhaka, Bangladesh.
Asia is particularly vulnerable and in general poorer nations are most at risk, the peer-reviewed scientific study said.
The study in the journal Environment and Urbanization doesn't say exactly what should be done, but it warns that it won't be cheap and it may involve moving lots of people and building protective engineering structures. And, it adds, countries should consider halting or reducing population growth there.
"Migration away from the zone at risk will be necessary but costly and hard to implement, so coastal settlements will also need to be modified to protect residents," said study co-author Gordon McGranahan of the International Institute for Environment and Development in London.
In a separate matter, the authoritative Intergovernmental Panel on Climate Change next week is expected to alert the world that coastlines already are showing the impact of sea-level rise and global warming and that it's expected to worsen. The IPCC -- which will issue a report on how climate change will effect human health, cities, agriculture, industry and different species -- is expected to say that about 100 million people each year could be flooded by rising seas by 2080.
"As the effects of climate change become increasingly clear, the location of the coastal settlements most at risk should also become evident," said the article by McGranahan, Deborah Balk of the City University of New York and Bridget Anderson of Columbia University.
"Unfortunately, by this time, most of the easier options for shifting settlement patterns, and modifying them so that they are better adapted to the risks of climate change, will have been foreclosed," the study said.
In February, the IPCC warned of sea-level rises of 18-58 centimeters (7-23 inches) by the end of the century, making coastal populations more vulnerable to flooding and more intense storms such as typhoons and hurricanes.
Some scientists also have said a far faster sea-level rise -- more than a meter (3.3 feet) per century -- could result from accelerated melting of the Greenland ice sheet or the collapse of the Western Antarctic ice sheet.
The new study said about 75 percent of all people living in vulnerable low-lying areas around the world are in Asia, and that at-risk poor nations such as Bangladesh and small island states like the Maldives should receive help dealing with the problem from rich Western countries, which released many of the world's greenhouse gases after industrializing.
Between 1994 and 2004, about one-third of the world's 1,562 flood disasters occurred in Asia, with half of the total 120,000 people killed living in that region, the study said.
Around the world, human settlement has long been drawn to coastal areas, with people often preferring to live within 100 kilometers (62 miles) of coasts and near major rivers. Today's threatened low-lying areas now contain about 2 percent of the world's land and 10 percent of its population, the report said.
Many such areas have long been vulnerable to natural disasters such as flooding and tropical storms, but climate change is likely to increase that risk, and governments will need a long lead time to respond effectively to the problem, the study said.
But such actions may not be easy.
"Migration away from lowest elevation coastal zones will be important, but can be costly and difficult to implement without causing severe disruptions," the study said. Still, it said, "Relatively small shifts in settlement location, out of a coastal plain onto more elevated ground, can make a major difference."
That is especially true in China, a country with an export-oriented economy that has created special economic zones in coastal locations.
Fast economic growth has been associated with very rapid coastward migration, with the population in low-lying areas growing at almost twice the national population growth rate between 1990 and 2000, the study said.
"Unless something is done, there is the possibility that, as well as the people living in the low-elevation coastal zone, China's economic success will be placed at risk," it said.
The study ranked the vulnerability of the world's countries in several different ways.
The five with the largest total population living in threatened coastal areas are China, India, Bangladesh, Vietnam and Indonesia.
A draft copy of the upcoming IPCC report, obtained by The Associated Press, said the costs and consequences of flooding are far higher in developing countries, compared with industrial nations. The report said for every person displaced by flooding in an industrial nation, 30 will be displaced in a developing country and 12 times more land is likely to be flooded in poorer countries than richer ones.
When nations are ranked by the largest total land areas in the zone, the leaders are Russia, Canada, the United States, China and Indonesia.
The draft copy of the upcoming IPCC report said in North America, the two biggest cities, Los Angeles and New York, are at risk of a combination of sea-level rise and storms with waters rising "up to several meters deep." By 2090, under a worst-case scenario, megafloods that normally would hit North America once every 100 years "could occur as frequently as every 3-4 years."
The five nations with the largest share of their land in the zone are the Bahamas, the Netherlands, Bangladesh, French Polynesia and Gambia.Source: Asia One
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