When New York City Mayor Michael Bloomberg unveiled PlaNYC in April, the press focused on just one of its 127 proposals for helping the city grow in an environmentally sustainable manner: a “congestion charge” applied to motorists in Manhattan’s key business districts. Bloomberg made headlines again this week when he called for replacing the city’s entire taxicab fleet with hybrid vehicles that pollute less. But there’s a lot more to PlaNYC than automobiles.

“It’s the other 126 proposals that are going to have an effect on all of the design professions,” observes Robert Yaro, president of the Regional Plan Association and a member of the mayor’s sustainability advisory board. The effect could in fact be huge. Buildings account for the lion’s share of New York’s current carbon output, 79 percent, according to a recent city audit. PlaNYC sets a goal of cutting the city’s carbon emissions 30 percent by the year 2030.

According to Yaro, 85 percent of the structures that will exist 23 years from now in New York are already standing today. This means that the biggest opportunity for architects, engineers, and construction firms lies in retrofitting the existing building stock. Robert Fox, AIA, a principal of Cook + Fox Architects who served on the advisory board with Yaro, adds that an estimated 400 million square feet of space may need to be renovated.

But there will be plenty of other opportunities in addition to retrofits. PlaNYC calls for creating 265,000 new housing units to accommodate an anticipated 1 million new residents. Since most of the city’s land is already developed, Yaro notes, the plan advocates reclaiming underutilized waterfront spaces, covering over railyards, and adapting abandoned schools and warehouses for residential use.

Among the anticipated projects is the development of air space above railroad tracks on Midtown Manhattan’s far west side, and the redevelopment of the area surrounding Madison Square Garden. Fox says that the latter project, whose heart will be a rebuilt Penn Station, “will yield tremendous opportunities” and Yaro compares its potential impact on the city to the construction of Rockefeller Center in the 1930s.

PlaNYC v. The London Plan: Which is Greener?

When New York City hosted a 40-city conference last week on strategies for surviving climate change, it was perhaps fitting that the opening reception took place at the Hearst Tower, a green building designed by London-based Foster & Partners. One month earlier, Mayor Michael Bloomberg released PlaNYC, a 127-point scheme to cut the city’s greenhouse-gas emissions; attracting the most attention was his proposal to create a toll for drivers who enter the city’s core—mimicking London’s congestion charge, established in 2003. As it happens, London is New York’s chief rival for cultural and financial primacy. It laid out its own scheme for combating global warming in 2004. Although the two plans share many similarities, New York’s could prove more far-reaching.

Other large cities tackling climate change concentrate on particular sectors: Chicago, for instance, encourages green roofs. London and New York are more comprehensive. Both focus on promoting development near mass transit and making buildings more energy-efficient. But New York asks architects and developers to make the most of existing spaces, while London encourages innovation on underdeveloped land.

Labeled a “spatial development strategy,” The London Plan laid the framework for constructing sustainable projects in underused areas such as the Lower Lea Valley, three miles east of the city’s center. As plan manager Debbie McMullen told a Manhattan audience in March, the possibility of developing that site drove Mayor Ken Livingstone’s successful bid to host the 2012 Olympic Games. PlaNYC, by contrast, envisions new housing built on decks over railyards and highways, and expediting brownfields remediation. It also calls for creating a public plaza or park within each of 50 community districts and relies on landscaping in parking lots and green roofs to capture storm water and spare overtaxed sewers. Most ambitiously, it seeks to use funds equal to 10 percent of the city’s energy expenses to retrofit municipal buildings with technologies that reduce carbon emissions by 30 percent—and it asks landlords of private buildings larger than 100,000 square feet to do the same.

London will likely pursue similarly audacious ideas on its own relatively blank canvas. Its strategy looks 15 years into the future, with goals that respond to European guidelines mandating the construction of more affordable housing. PlaNYC, meanwhile, sets 2030 as its deadline. Before then, it must pass several hurdles. Bloomberg will seek funds from the newly announced Clinton Climate Initiative, but he needs state authorization for other initiatives. Also, landlord groups such as the Real Estate Board of New York want more time to implement improvements.