Rising sea levels threaten world’s major coastal cities
By Thomas Wagner
Article Launched: 03/28/2007 01:45:49 AM PDT
LONDON – More than two-thirds of the world’s large cities are in areas vulnerable to global warming and rising sea levels, and millions of people are at risk of being swamped by flooding and intense storms, according to a study released today.
In all, 634 million people live in threatened coastal areas worldwide – defined as those lying at less than 33 feet above sea level – and the number is growing, said the study published in the journal Environment and Urbanization.
More than 180 countries have populations in low-elevation coastal zones, and about 70 percent of those have urban areas of more than 5 million people that are under threat. Among them: Tokyo; New York; Mumbai, India; Shanghai, China; Jakarta, Indonesia; and Dhaka, Bangladesh.
The peer-reviewed scientific study said it is the first to identify the world’s low-lying coastal areas that are vulnerable to global warming and rising sea levels. It said 75 percent of all people living in vulnerable areas are in Asia, with poorer nations most at risk.
The study gives no time frame for rising sea levels or the potential flooding in individual countries. It warns, however, that the solution to the problem will not be cheap and may involve relocating many people and building protective engineering structures. It adds that nations should consider halting or reducing population growth in coastal areas.
“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 Gordon McGranahan of the International Institute for Environment and Development in London, a co-author of the study.
The institute publishes the journal Environment and Urbanization. The other two co-authors of the study are Deborah Balk of City University of New York and Bridget Anderson of Columbia University.
Separately, the authoritative Intergovernmental Panel on Climate Change said in a draft copy of a report expected to be released next week that coastlines already are showing the impact of sea-level rise. The draft copy, which was obtained by the Associated Press, said about 100 million people each year could be flooded by rising seas by 2080.
The draft copy warned that the two biggest cities in North America – Los Angeles and New York – are at risk of a combination of sea-level rise and violent storms. By 2090, under a worst-case scenario, floods that normally hit North America once every 100 years “could occur as frequently as every 3-4 years,” the draft said.
In February, the IPCC warned of sea-level rises of 7 to 23 inches by the end of the century because of global warming, making coastal populations vulnerable to flooding and more intense hurricanes and typhoons.
Asia is particularly vulnerable, the study said. The five nations with the largest total population living in endangered coastal areas are all in Asia: China, India, Bangladesh, Vietnam and Indonesia.
From 1994 to 2004, about one-third of the world’s 1,562 flood disasters occurred in Asia, with half of the total 120,000 people killed by floods from that region, the study said. In addition, more than 200,000 people were killed by the Indian Ocean tsunami of 2004.
“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, such as Shanghai. Fast economic growth has been associated with rapid coastward migration, with the population in low-lying areas growing at almost twice the national population growth rate from 1990 to 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.