As we become an ever more urban species, cities will be a crucial front in the fight against climate change. Scientists, architects and planners must join forces to make our metropolitan future clean and sustainable.
Humanity has passed a milestone: more people live in cities than in rural areas. The current rate of urbanization is unprecedented in our history. In 1950, only 29% of people lived in cities; by 2050, 70% are projected to do so — most of them in poorer countries. Among many other issues, this rapid concentration makes cities a front line in the battles against climate change and air pollution. Confronting the challenges of rampant urbanization demands integrated, multidisciplinary approaches, and new thinking.
Many poorer countries have a rich tradition of adapting buildings to local practices.
Take the building boom associated with the increased wealth of urban areas, and its impact on greenhouse-gas emissions. In China alone, the United Nations Environmental Programme estimates that energy demand for heating homes built over the next decade could increase by some 430 terawatt-hours, or 4% of China's total energy use in 2003. Worldwide, the energy consumed by buildings already accounts for around 45% of greenhouse-gas emissions.
Fortunately, researchers in Germany and elsewhere have already shown that they can reduce that energy consumption by 80–90%, just by overhauling obsolete building designs and using existing technologies (see Nature 452, 520–523; 2008). These ultra-efficient buildings demand that planners, architects, engineers and building scientists work together from the outset, and require higher levels of expertise than conventional buildings. But such buildings are often cheaper than those built using conventional methods. Research is also needed to develop technologies, materials and energy concepts, but green building research today is fragmented and poorly funded.
Expanding cities must embrace such technologies and strategies — and not just in the developed nations. It may seem utopian to promote these innovations in emerging and developing-world megacities, many of whose inhabitants can barely afford a roof over their heads. But those countries have already shown a gift for technological fast-forwarding, for example, by leapfrogging the need for landline infrastructure to embrace mobile phones. And many poorer countries have a rich tradition of adapting buildings to local practices, environments and climates — a home-grown approach to integrated design that has been all but been lost in the West. They now have an opportunity to combine these traditional approaches with modern technologies.
Integrated thinking is also needed to mitigate urban air pollution, which is becoming a serious health and environmental risk in many regions — as shown by China's struggle to clean up Beijing's air for the Olympics. Understanding air pollution will require researchers from multiple disciplines, from atmospheric chemistry to meteorology, working over scales from street level to global (see page 142). And reducing it will require integrated policies for urban planning, transport and housing — not least to reduce the use of cars.
This unified approach is not entirely new: the Brazilian city of Curitiba has linked urban planning, transport and housing development for decades; a large majority of its nearly 2 million inhabitants now use public transport and recycle waste. But new city design and planning tools are making it considerably easier. Modern simulation software, for example, allows designers to do full structural analyses of buildings and model their energy balances in three dimensions. Likewise, geographical software allows planners to model the impact of planning scenarios on variables such as traffic and emissions.
Integrated thinking and planning requires a cultural shift: most urban development has been laissez-faire. Yet there are signs that such a shift has begun. In California, state lawmakers are considering a bill to restrict transportation subsidies to compact developments that reduce the need for car travel. If passed, this would be the first legislation in the United States to tie urban planning to the control of greenhouse gases. And China plans to build one of the world's first eco-cities off the coast of Shanghai. Dongtan aims to be free of cars, energy-independent — thanks to energy-efficient buildings, plus the extensive use of renewables and geothermal strategies for heating and cooling — and home to half a million people.
Such innovations need to be encouraged, expanded and accelerated — everywhere on the planet.
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Turning blight into bloom. Nature 455, 137 (2008). https://doi.org/10.1038/455137a