By Janny Scott

A swelling population, an overheated real estate market and the biggest building boom in 30 years are fueling a counterrevolution in New York City: Dozens of neighborhoods have asked the Bloomberg administration to rewrite zoning rules to rein in what residents see as runaway development and growth.

In what some housing experts are calling "the downzoning uprising," communities throughout the city want to see an end to an influx of apartments, additional people, and what they consider McMansions - and to preserve neighborhoods of limestone town houses, 1950's ranch houses, even humble wood-frame houses wrapped in aluminum siding.

The administration has agreed, with enthusiasm. Since 2002, 42 rezonings "to preserve neighborhood character," as the administration puts it, have been approved or are under review. About 3,600 blocks have been rezoned, and more proposals are on the way. By contrast, officials say, the city approved only eight such rezonings in the three years before 2002.

The demand to control neighborhood density comes as the city's population is projected to reach 8.4 million by 2010, up from an estimated 8.1 million today. There is already a shortage of housing that moderate and middle-income people can afford. So the push for downzoning pits the rights of neighborhoods against the city's broader need to equitably accommodate its growth.

The downzoning issue also underscores the ambivalence of many New Yorkers toward density. New Yorkers celebrate the city's vitality, changeability and allure, and many recognize density as somehow crucial to New York's energy and life. Yet they balk at the prospect of too much density and change close to home - their homes.

"New York's greatness is based on a concentration of population," said Julia Vitullo-Martin, a senior fellow at the Manhattan Institute who specializes in housing, planning and development. "And New York's great neighborhoods are the ones served by public transportation and built for density."

She said there had often been "an odd antidensity zeitgeist in New York," then added, "Density is good for New York."

Those in favor of the recent downzonings say they will protect neighborhoods against out-of-scale development, especially in places without the infrastructure needed to handle growth. When balanced by increases in density elsewhere, they say, the downzonings will also stop real estate speculation and keep communities stable.

"If you allow the character of a neighborhood to be eroded, the people who live in that neighborhood will leave the city," said Amanda M. Burden, chairwoman of the City Planning Commission. "We can't allow that to happen. Protecting these different neighborhoods, we are providing New Yorkers with a diversity of housing choices."

But others worry that the downzonings are beginning to outweigh the effect of upzonings elsewhere in the city. It is easier, they say, to decrease density than to increase it, especially in an election year. They worry that rezoning the neighborhoods will make them more homogenous, and the home prices higher.

"There are real reasons why people feel they'd rather not have new development, good and bad," said Brad Lander, executive director of the Pratt Institute Center for Community and Environmental Development. But, he added, "It seems to me that if you refuse growth, you are either implicitly saying we should change our immigration policies and not let people in, or immigrants should live in basements and attics or in the Poconos."

The rush to rezone primarily to reduce density has been felt throughout the city. Much of Staten Island, the fastest-growing county in the state in the 1990's, was rezoned last year to reduce the density of new residential development. In Queens, the city has agreed to rezone Bayside, Cambria Heights and half a dozen other neighborhoods. Rezonings of Whitestone and College Point are also in the works.

In the Bronx, proposals for Morris Park, Woodlawn, Olinville and Riverdale are under public review. Pelham Gardens, Throgs Neck and others have already been rezoned. So have Bensonhurst and Park Slope in Brooklyn. Even in Manhattan, where the city has recently rezoned former manufacturing areas to make high-rise residential development possible, it has at the same time downzoned parts of the West Village.

"Because of confidence in the city, investment in housing and growth in population, we are finding neighborhoods where there's a real mismatch between the ability to build and the character of the neighborhood," said Ms. Burden, who is also the director of the Department of City Planning. "That's where communities have come to us, in every single borough, saying, 'Protect our neighborhood.' "

The problem, as she and others see it, is that the city's zoning resolution had its last major revision in 1961 - at a time when some imagined the city's population to be heading toward 16 million. Many areas ended up zoned for more development than actually occurred. As a result, much of Staten Island, Queens, Brooklyn and the Bronx are less densely developed than zoning permits. Until recently, it did not really matter.

But the record-breaking growth in the city's population in the 1990's and the real estate boom that followed made it lucrative for developers to begin taking advantage of the old rules. They started replacing moderate-size homes with big ones, doubling the number of houses on lots, building multifamily housing in single-family neighborhoods. Longtime residents balked.

"People generally plant themselves in neighborhoods for a reason," said Tony Avella, a city councilman from northeast Queens who made overdevelopment a campaign issue when he ran for office in 2001. "It's usually the quality of life. If we allow the quality of life and the neighborhood character to disappear because of overdevelopment, then you lose something that the city will never get back."

Mr. Avella began making the rounds of civic associations in Queens and Brooklyn, spreading the downzoning gospel. In his own district, he hired a planning consultant, Paul Graziano, to do an independent zoning study and make recommendations. Then the Department of City Planning was asked to rewrite much of the district's zoning.

"We thought this would be a good way to jump-start this issue not only in my district but throughout the city," Mr. Avella said. "It really started a groundswell. People started to realize: 'This is a problem in my neighborhood. You know what? This is leading to overcrowding in my school. This is why we have a traffic problem. We're getting sewer backups because the infrastructure can't handle these developments.' People started to realize, 'Wow, this really does affect our quality of life.' "

Mr. Avella had his doubts about a balanced approach.

"There had always been a philosophy in previous administrations in City Planning: 'Well, if we're going to do a downzoning, we have to do an upzoning, too,' " he said. "My argument is, if a neighborhood is improperly zoned and wants a downzoning, they shouldn't have to do an upzoning. They should have it regardless of what happens somewhere else."

One of the first communities in his district to be rezoned was Bayside. There, most of the housing consisted of one- and two-family detached and semidetached homes, but the old zoning allowed row houses and apartment houses as well. So Bayside was rezoned in April to permit for the most part only one- and two-family houses in the future, with new limits on floor area and height to stop out-of-scale development. Similar changes are in the works in other communities. Sean M. Walsh, president of the Queens Civic Congress, attributes the communities' success in part to timing. "We seem to be more successful in the election cycle than in the nonelection cycle," he said. "Because I think you need votes and you try to appease or please people in the neighborhoods."

The impact of downzonings on the city's property tax revenues is not clear, housing experts said. In theory, a downzoning could hurt tax revenues in the short run by limiting new construction; but in the longer run, it could help them if it enhanced the viability of a neighborhood and raised property values.

Rachaele Raynoff, a spokeswoman for the Department of City Planning, said the city was doing nothing different this year than it had in the past. Mayor Michael R. Bloomberg's administration took office with an economic development plan for the five boroughs, she said, and when it encountered concerns about development pressures in the neighborhoods, the city incorporated those concerns.

Not everyone sees the rezonings as an unalloyed good. Mr. Lander said many of the recent downzonings have not been balanced with upzonings nearby, even in neighborhoods that he believes have the infrastructure to accommodate growth.

For example, he said: "They've effectively downzoned all of Staten Island. That's not smart and balanced rezoning."

He added: "This is a real problem throughout the city, preserving what people love about their neighborhoods and equitably meeting the needs of a growing city. But a fair-share approach to that problem is to ask places to balance it within some reasonable geography, rather than saying: 'We'll preserve our neighborhood. Somebody else should deal with the growth.' "

Vicki Been, director of the Furman Center for Real Estate and Urban Policy at New York University and an expert on land-use law, said there is usually a trade-off between low density and affordability. "If people want low density, then there's a cost to affordability, and vice versa," she said. "If you're limiting the building in one place and you've got a growing population and increased housing demand, you've got to provide for it someplace."

Ms. Burden pointed out that the administration has encouraged housing development. The recent rezonings of former manufacturing areas in Greenpoint and Williamsburg in Brooklyn and West Chelsea and the Hudson Yards in Manhattan are expected to produce 29,000 new units. Other possible areas of growth in the future, she said, include Long Island City in Queens and the area known as the Hub in the Bronx.

On a recent afternoon, Mr. Graziano, the 34-year-old planning consultant hired by Councilman Avella, drove through the northeast Queens neighborhoods where he has spent his life, and that he is now intent on preserving. He admired the charm of north Flushing's tree-lined streets, fulminated against development excesses and pondered the struggle still to come.

"For better or worse, this has been kind of a revolution that's gone on here," Mr. Graziano had said earlier. "A very quiet, nontraditional type of revolution. I think it has changed the way that City Planning operates. It has changed the discussion. Which is all that I wanted."

He added: "These neighborhoods substantially have not changed in 40 years. What we're trying to do is make sure they are recognizable 40 years from now. I don't think there's anything wrong with that. In fact, in many other places in the country, that is celebrated. So why shouldn't we celebrate it as well?"