Fighting climate change means building dense, diverse, walkable cities.

“Let me add to the complexity of the situation we find ourselves in: At the same time we’re solving for climate change, we’re going to be building cities for 3 billion people,” said the urban designer Peter Calthorpe at the beginning of his talk at TED 2017. By 2050, he said, we will see the urban population double, and if we don’t manage to sustainably and practically build to accommodate that growth, “I’m not sure that all the climate solutions in the world will help save mankind,” Calthorpe said.


But there is a real enemy to target in this situation, Calthorpe said, and it is sprawl. When most people think of sprawl, they think of the low-lying scattering of buildings that circle metropolises and eventually fade into the suburban and the rural. But sprawl, Calthorpe said, can happen anywhere, at any density: Its key attribute is that it isolates people.

Separating people into economic enclaves and land-use enclaves, dividing them from nature, and prioritizing vehicle transportation (all key features of sprawl) doesn’t allow for the kind of close-knit, communicative growth that allows cities to develop in a way that hinders, not hastens, climate change.

Future compact development could slash California’s hypothetical carbon footprint. [Photo: senaiaksoy/iStock]“The antidote to sprawl is what we need to be thinking about,” Calthorpe said.

How, exactly, is the main question. Calthorpe’s software and urban modeling company, Calthorpe Analytics, has developed a tool called UrbanFootprint that gives planners and developers a way to test out the impact of future development models. For the state of California, Calthorpe Analytics used UrbanFootprint mapped out two different scenarios for 2050–one in which the state continued its “business as usual” sprawl-driven development and one in which it shifted to compact development, prioritizing dense housing and mixed-use streets.

Contrasted to the sprawl model, compact development slashed the California’s hypothetical carbon footprint in half by reducing the miles traveled by vehicles by 10,500 and drove down the health care costs associated with inhaling smog and embracing a sedentary lifestyle. “Why not just stop polluting?” Calthorpe asked. “Why not use our feet and bikes more?”

The economic viability of compact development, he added, even has the potential to sway typically pro-vehicle and anti-regulation conservative policymakers.

And for an example of somewhere already in the midst of overhauling its development strategy, Calthorpe turned to China, whose model of sprawl–tall, densely located building blocks lacking mixed-use streets and opportunities for human interaction–has long been a threat to its sustainability goals. Calthorpe’s firm developed a set of seven principles for the country to apply to its cities: preserving natural ecologies; creating mixed-use and mixed-population neighborhoods; designing walkable streets and human-scale neighborhoods; promote biking; increase the connectivity of the road systems; develop efficient transit systems; and match density to transit capacity.


While China is in the process of integrating these principles into its cities, they’re guidelines that can and should be adopted worldwide. Only by promoting what works for humans and fostering social wellbeing, economic equality, and a sense of connectedness, will we stand a chance, as a global society, to fight climate change. “The way we shape cities is a manifestation of the kind of humanity we bring to bear,” Calthorpe said.