People tend to picture cities, particularly in the developing world, as urban wastelands belching out pollution, breeding sickness, promoting endless consumption and driving population increases. But cities also have a huge potential for getting us out of the very environmental mess they’ve helped get us into, according to some researchers.

Well-designed cities, with dense housing and efficient mass transit, can reduce energy use and emissions per person, and the opportunities they provide for women puts the lid on population growth, ultimately reducing the immense strain humans are putting on nature. Counterintuitive as it may sound to anyone who’s ever breathed in urban smog or looked out onto a natural landscape punctuated by buildings, cities are integral to this rosy vision of the future.

To begin, urban areas occupy only a small fraction of the Earth’s land surface — below 3% — but house a growing majority of its population. More than half of the people in the world live in urban areas today. By 2050, the United Nations estimates, the proportion will approach 70%. If more people are geographically concentrated, then we encroach less on other lands.

Of course, these cities will still rely heavily on resources outside the city in order to operate. But as cities become more efficient and circular systems become the norm, the need for resource extraction is also set to decline. There are many surprising reasons why big cities could end up saving the environment. Check them out right here.