15 jun 08 | The New York Times

Scraping the sky, and then some

By Amy Cortese

The world's population is expected to climb to nine billion by the middle of the century, from six and a half billion today, according to the United Nations , and a staggering number of those people are likely to be living in big cities.

A pressing question for developers and urban planners is how to accommodate the growing urban masses, especially in developing countries of Asia and Africa. But one point is clear: The skyscraper will play a central role.

Nearly seven years after the collapse of the World Trade Center in New York portended a pullback from cloud-grazing construction, the world is in the midst of a huge wave of tall building construction, both in number and in size. Some 36 buildings rise more than 300 meters, or roughly 1,000 feet, the threshold generally used to define "supertall" buildings, according to the Council on Tall Buildings and Urban Habitat, a nonprofit organization based at the Illinois Institute of Technology. An additional 69 supertalls are under construction, the council estimates.

Some of the most ambitious developments are in the petro-fueled economies of the Middle East and Russia. Among the most anticipated is the $1 billion Burj Dubai, a massive tower being developed by Emaar Properties in the United Arab Emirates. Although it is not yet complete, the tower has already surpassed the current record holder: Taipei 101 in Taiwan.

The final height has been a closely guarded secret, though the Burj Dubai's 160-plus floors and spire are expected to reach more than 2,600 feet into the sky when it is completed next year, nearly 1,000 feet more than Taipei 101, which was completed in 2004. To put it in perspective, that's almost an entire Chrysler Building higher.

Not to be outdone, the Saudi Arabian multibillionaire Prince al-Walid bin Talal recently unveiled plans for a mile-high tower near the Red Sea port of Jeddah that, if built, would be twice the height of the Burj Dubai.

"It is the modern equivalent of New York in the 1920s," said David Scott, a principal at Arup, an engineering firm, and the chairman of the Council on Tall Buildings and Urban Habitat.

A three-part exhibition in Manhattan at the Skyscraper Museum -- "Future City: 20|21" -- explores this theme by comparing New York in the 1920s and '30s, when audacious skyscrapers rose up and captured the public's imagination, with its modern-day peers in Asia, namely Hong Kong and Shanghai. "New York Modern," the first leg of the exhibit, concludes later this month, and will be followed by "Vertical Cities: Hong Kong|New York." An examination of Shanghai is planned for next year.

As the show suggests, the center of gravity today has shifted from North America and Europe to Asia and the Middle East, where supertalls are rising at a frenetic pace. (In Dubai, the construction crane is jokingly called the national bird.) Supertalls are also going up in countries like India, Kazakhstan and Brazil.

The trend, said Carol Willis, an urban historian and director of the Skyscraper Museum, reflects the expanding economies of those regions and their desire to compete for international status and business.

In contrast, she says that large developments in New York and other Western cities these days are likely to encounter public opposition -- as evidenced by initial public reaction to Forrest City Ratner's plan for the 22-acre Atlantic Yards in Brooklyn, and Jean Nouvel's soaring Midtown Manhattan tower, commissioned by Hines, an international real estate developer.

And tighter credit in the United States has developers increasingly looking at emerging markets.

"People are looking at where else they can put their money to work," said Jeff Cushman, executive managing director of Cushman & Wakefield, the real estate services firm.

The newest skyscrapers are breaking old molds. In the United States, the tallest buildings have tended to be office towers, but in Asia and the Middle East, the towers now going up are often residential or mixed-use buildings, with developers selling off residential units to generate cash flow. The new towers are also likely to be built from concrete or composite materials rather than traditional steel and to incorporate so-called green design features.

In many cases, they serve as a focal point for larger-scale master plans. The Burj, for example, is at the center of a $20 billion, 500-acre development of downtown Dubai. Residential units in the Burj are selling for as high as $3,500 a square foot. The tower's presence has already increased the value of nearby properties by as much as 60 percent, according to Emaar.

To get a sense of the pace of change, the Council on Tall Buildings has projected what will be the tallest 20 buildings in 2020, measured by height from sidewalk to their architectural top. (Its researchers included only buildings that have developers and financing and have moved beyond the concept phase, but there is no certainty that they will be built, especially given the current economic downturn. The list does not include developments that are being planned but kept under wraps, like the Saudi mile-high tower.)

Icons like the Empire State Building in New York and the Sears Tower in Chicago, which have long been enshrined among the tallest buildings in the world, are bumped from the list. The Petronas Towers in Kuala Lumpur, currently just behind Taipei 101, fall to 20th place.

Only two towers in the United States make the list. At 2,000 feet and 150 stories, the Chicago Spire, a twisting residential tower designed by Santiago Calatrava that broke ground last summer, ranks sixth on the list. It is being developed by the Shelbourne Development Group, a developer based in Dublin that took over the project from Fordham Development. One World Trade Center in New York, also known as the Freedom Tower, from Silverstein Properties and designed by Skidmore, Owings & Merrill, comes in at No. 11, at a symbolic 1,776 feet.

By that time, the fruits of other urban-planning ideas may emerge. At the World Science Festival last month, a session titled "Future Cities" explored ideas like vertical urban farms growing local produce and zero-carbon mini cars that can nest like airport luggage carts when not in use.