As we address the potentially catastrophic consequences of climate change over the next three decades, cities will be the decisive factor. Nearly 80 percent of carbon dioxide emissions — the main cause of global warming — already emanate from cities, and that number is expected to grow as the world’s population moves toward the 9 billion mark and congregates increasingly in urban centers.
We have opportunities to change this potentially disastrous course, provided that policymakers and business leaders take action soon. The key is in urban infrastructure: the systems of transportation, energy, water, building, and communications that support cities, distinguish them, and contribute so much to their vitality. Estimates from a new research study suggest that cities will have to spend an astonishing US$350 trillion — seven times the current global GDP — on building, operating, and maintaining these infrastructure systems over the next 30 years to accommodate the growth in their population. (See “Cities and Global Warming: Doing the Math,” at the end of this article.) If this investment is managed along a business-as-usual path, cities will become a growing force for environmental destruction. If, on the other hand, government and business leaders direct enough of this spending to significantly lower-carbon initiatives, then the cities of the world will become a primary source of ecological rejuvenation.
All cities will have to take action to limit carbon emissions, but it will be particularly important for two categories of city, mostly in the developing world. The first category is rapidly growing smaller cities with current populations under 1 million, where the largest population gains and infrastructure expansions will occur. They have fewer resources than other metropolitan areas, but they have an upstart’s advantage: They are still in the formative years of infrastructure development and thus have smaller carbon footprints than their more established counterparts. The other category is made up of the so-called second-tier cities, which have little name recognition outside their home countries but burgeoning economies and rapidly growing, multimillion populations. Both types of cities have the opportunity — and the urgent need — to plan for better infrastructure.
The Three Prerequisites for Change
Cities are immensely diverse, but the case for a new approach to sustainable urban infrastructure is universal. Whether in Sweden or China, Germany or Nigeria, urban leaders need to focus their infrastructure spending on three kinds of activities. These three practices, taken together, represent “must-do” prerequisites for any green strategy — especially one that hopes to avoid the disastrous consequences of climate change.
- Adopting aggressive energy reduction plans and setting goals for both new and existing infrastructure
- Investing in cutting-edge technological advances
- Implementing innovative financing strategies
These conclusions come from “Reinventing the City,” the 2010 global study conducted by the World Wide Fund for Nature (WWF) and supported by Booz & Company. The study analyzed data on population, environmental measures, construction and infrastructure investments, and the best practices that successful cities use when tackling the challenge of sustainability.
We expanded on this analysis by interviewing city officials in different regions about their experiences as they implemented policies to improve planning, technology adoption, and investment. We then identified clear success factors. The most successful cities are those that combine efforts to reduce carbon emissions in the future with a focus on improving livability for their citizens today. They also take a long-term view in formulating plans and policies, and work to make them relevant to their own particular situations. The cities described in this article are far-flung and have vastly different populations and resources, and none of them have a perfect record in pursuing sustainability. But they share a commitment to reshaping our common urban future and exploring the opportunities that will arise. They are the pathfinders that all cities — especially the fast-growing categories — can and must learn from.

