Our ever-growing global population wants to live in cities, and we have some catching up to do. The UN predicts that two-thirds of the world will live in cities by 2050, and the majority of that urbanization will happen in developing areas of Africa and Asia.

What will that demand from us? New approaches to urban infrastructure, transportation, and resource management: Before a staggering number of people move into the world’s cities, we need to make the urban ecosystem more efficient and more environmentally friendly.

Every urban system that might seem closed—from transportation to waste management to construction—is just one piece of the larger, integrated system we need to support an exponentially growing population. To make the whole structure sustainable and efficient, cities need to embrace advances that will allow for rapid expansion, an upgraded, coordinated infrastructure, and a substantial reduction in environmental impact.

The future of urban living is exciting. It also comes with a set of pressing concerns. If we want to make our future cities equitable and sustainable, we must be willing to move fast.