NEW YORK CITY: An Island Ecology.

NEW YORK CITY, WITH MORE THAN SEVEN MILLION PEOPLE, SPILLS OUT OVER 378 SQUARE MILES OF LAND separated by such waterways as the Hudson, East and Harlem Rivers, Long Island Sound and the Atlantic Ocean. The city, one of America's most diverse urban centers, is held together by a complex network of public works infrastructure, including roads, toll bridges, subway tunnels, water mains, gas lines, and millions of miles of telephone and television cables and electrical conduit.

It's a difficult city to run on a good day: In 1996, a "report card" prepared by the city's former U.S. Army Corps of Engineers chief gave New York's infrastructure failing grades, particularly for its aging water mains and solid waste treatment system, which dumps raw sewage into city harbors during storms.

So what happens when things get really bad? On December 11, 1992 a nor'easter storm hit the great city head on. With wind gusts of up to 90 miles per hour and water surges eight-and-one-half feet above mean sea level, New York's transportation infrastructure sputtered to a halt. Four million subway riders were stranded. Franklin Delano Roosevelt Drive, the main highway along the east side of Manhattan, flooded up to four and one-half feet in some areas, and LaGuardia International Airport, only seven feet above sea level, grounded flights for the day. In the end, the federal disaster assistance totaled $233.6 million, according to Environmental Defense.

Was the storm a once-in-a-century fluke? Unlikely. In August of 1999, a single early morning thunderstorm crippled the city's transportation and drainage system once again. Since global warming brings with it the certainty of rising sea level and stormier weather, the city's aging infrastructure and delicate natural balance face unheard-of challenges.

Vivien Gornitz, associate research scientist at NASA's Goddard Institute for Space Studies, points toward a rectangular box jutting out of the Hudson in lower Manhattan, near a guarded U.S. Coast Guard booth. "That tide gauge uses an acoustic device to record the level of the sea's surface," she explains. "It takes a reading every six minutes." Gornitz and other researchers from Columbia University, New York University and Montclair State University in New Jersey study the Metro East Coast (MEC) Region, which includes greater New York, Northern New Jersey and Southern Connecticut, for the U.S. National Assessment of the Potential Consequences of Climate Variability and Change for the Nation.

One of the things that troubles Gornitz is all the recent construction at the water's edge. "Look, you can see it's on both sides of the river," she gestures, her arm taking in both sides of the Hudson just north of the World Trade Center. Gornitz fears that all the luxurious waterfront condominiums and commercial businesses are taking a risk that will increase dramatically as the new century progresses.

The most conservative climate change model used for the MEC study doesn't allow for rising greenhouse gas emissions; it merely projects the effects of the current rate of sea level rise. It predicts that, by the end of the century, we will be seeing 100-year floods every 50 years. "In the worst-case scenario, it could be as often as every four to five years," Gornitz adds. And to further exacerbate the problem, the greater New York area is still experiencing land subsidence triggered by the glacial retreat that occurred more than 10,000 years ago.

"It really would become a serious economic burden for the city," says Klaus Jacob, senior research scientist at Columbia University's Lamont-Doherty Earth Observatory. "The current flood insurance program doesn't account for 100 years from now, and that's no way to plan for the future, especially a sustainable one."

The borough of Brooklyn, now home to over two million people, was once largely marshland, but the re-designing of this landscape for exclusive human use has taken away a valuable, natural protection in times of flood. "If you could imagine just putting a big sponge in front of lower Manhattan, that's what it would be like if there was a wetland there," explains Alex Kolker, a graduate student studying ecology and evolution at the State University of New York at Stony Brook.

One way to limit the loss of these flood barriers is to give coastal areas room to migrate inland. The U.S. Army Corps of Engineers and the New York State Department of Environmental Conservation oversee current waterfront development. But according to Ellen Kracauer Hartig, a research associate at Columbia's Center for Climate Systems Research, applicants can apply to bypass these regulations, and permission is frequently granted. "At this time, the state gives out those permits easily," she says. That's an understatement. In 1998, the Corps rejected only 3.2 percent of major wetlands projects.

Global warming has also begun to affect the city's health. "In New York City, asthma rates in some neighborhoods are among the highest in the nation," explains Pat Kinney, an environmental health scientist at Columbia's Joseph L. Maleman School of Public Health. Kinney points out the well-established connection between air pollution, temperature, and rates of hospitalization and death. "What is new, is seeing how it all relates to climate change," he says, adding that raising the temperature in urban areas like New York, where there is limited vegetation to reflect heat and lots of concrete to absorb it, exacerbates health problems.

According to a 1996 American Meteorological Society report, an average of 300 people a year die of heat stress in New York City. And there's a socioeconomic factor, too, explains Kinney: "Poor people, and especially elderly poor people, are most vulnerable to heat stress." Other potential problems are the spread of vector-borne diseases that thrive in warmer temperatures, and increased levels of ozone, a respiratory irritant chemical, at the ground level.

Coordinated planning for these eventualities has been minimal. Rae Zimmerman, a New York University professor and director of the Institute for Civil Infrastructure Systems, cautions that there is little cooperation between city agencies affected by climate change, and long-range planning is often the first thing cut from squeezed budgets.

Because congressional action is necessary for national global warming legislation, say climate change crusaders, the outcome of the November elections is crucial. But Klaus Jacob notes sardonically, "Whether Congress wants to address it or not, sea level will rise." CONTACT: Metropolitan East Coast Assessment, [phone], http://metroeast_climate.ciesin.columbia.edu.

SHERRY BARNES is a freelance writer in Sitka, Alaska.