Editor's note: TED is a nonprofit organization devoted to "Ideas worth spreading," which it makes available through talks posted on its website. Joshua Prince-Ramus is Principal of REX, an architecture firm responsible for the AT&T Performing Arts Center's Dee and Charles Wyly Theatre in Dallas, Texas, and Museum Plaza, a 62-story mixed-use skyscraper housing a contemporary art center in Louisville, Kentucky. Randolph R. Croxton is president of Croxton Collaborative Architects PC., which has received the National Leadership Award from the U.S. Green Building Council. Tuomas Toivonen is a Helsinki-based architect and founder of NOW, an architecture firm, and is an artist who performs and records music and produces installations and performance art.
(CNN) -- The United States has the third largest ecological footprint per capita, behind only the United Arab Emirates and Saudi Arabia. We face an extraordinary challenge in overcoming our environmental deficit.
Unfortunately, the American building-design community's vision of sustainability is myopically focused on increasing the energy efficiency and reducing the embodied carbon of individual buildings. So-called "green" buildings are simply not sustainable if, for example:
• Their occupants drive long distances every day.
• The energy they consume is carbon-intensive.
• Their technology is too complicated to use or too difficult to maintain.
• Their impact stops at the property line.
• They deny the use of pre-existing infrastructure or building fabric.
• They are conceived in isolation from larger, systemic environmental change.
A truly sustainable strategy cannot externalize any factors. An off-the-grid energy-efficient building in the suburbs actually has a high carbon footprint when considering the auto-dependent lifestyle it encourages. Shortening the daily commute of a typical person by six miles saves as much carbon as a 50 percent reduction in energy use for home heating.
"Green" buildings alone are not enough to divert our perilous course. A broader vision of sustainability is imperative to meet America's challenge.
We must decide if we are willing to change our behavior: to migrate toward more populated, more diverse, more sustainable cities. Only by changing behavior -- particularly suburban sprawl and its accompanying carbon intensive lifestyle -- can the United States reach ecological balance.
Strategies for maximizing the potential of our urban cores' existing vitality and infrastructure must be the basis for any definition of sustainability.
In short, we must make the most of what we already have. We must overcome the growing perception that new "green" is our salvation. By analogy, the electric hybrid Toyota Prius is an energy-efficient car. However, when accounting for the energy used to manufacture a new Prius, one would actually save more energy by continuing to drive a mid-'90s Geo Metro.
The same logic applies to our built environment. While all new buildings must be designed to meet the highest environmental standards, updating and/or adaptively reusing existing buildings close to the infrastructure our nation has built over the last 100 years is often far more sustainable than constructing new "green" buildings in the suburbs (or even downtown).
A sustainable future therefore demands that population be funneled back into America's urban cores, within easy reach of existing infrastructure and amenities such as schools, libraries, recreation facilities, theaters, restaurants and retail, whose carbon debt has already been paid off. Ultimately, urban living itself is the embodiment of sustainability.
The following strategies can effectively incentivize U.S. growth and migration to move toward more dense and diverse cities, while simultaneously enriching natural resources:
• Establish growth boundaries between city and nature that allow both to reach their full potential. Cities become more dense, diverse and efficient, while nature and farmland are protected against sprawl. Seemingly radical, growth boundaries are not a new idea in the United States. For example, the Urban Growth Boundaries established by the State of Oregon in 1973 have yielded more than 30 years of smart, sustainable development in cities such as Portland.
• Create regional and nationwide marketplaces that allow rural and suburban landowners outside growth boundaries to transfer their development rights to areas where urban growth is desirable. Again, while seemingly radical, this strategy has already been implemented since the 1980s in Lancaster County, Pennsylvania, to stem the destruction of Amish farmland and heritage.
• Develop a national ecological balance plan that steers development at the scale of buildings, infrastructure and ecosystem services through a comprehensive framework of guidelines and indicators.
• Devise a quantitative indicator that analyzes and coordinates population density, programmatic diversity and low-carbon travel. This metric would provide policy makers, planners, developers and citizens with a common understanding of the underlying patterns that shape their community's carbon footprint, and inform consensus-driven systemic action, such as the drawing of growth boundaries.
• Develop new types of urban structures that, by design, can adapt to a rich variety of unanticipated uses and accommodate new construction technologies as they evolve. This new class of structures would engender the organic, heterogeneous evolution that originally shaped America's cities.
While most of these strategies fall outside the conventional scope of the building-design community, perhaps a broader vision of design is equally imperative, where architects and engineers claim their role in positively changing human behavior, not just advancing building technology.
The opinions expressed in this commentary are solely those of the co-authors.