World map showing the 400-plus large cities that sit in biodiversity hotspots
World map showing the 400-plus large cities that sit in biodiversity hotspots Atlas for the End of the World

If cities keep growing as they do now, nearly 400 of them will sprawl into the habitats of endangered species by 2030.

By 2030, the world is expected to add another billion people or so, bringing the total population to roughly 8.5 billion. And with humans becoming increasingly urban, sprawl will only get worse, taking up precious space that wild birds, mammals, plants, and the like can still call home.

In fact, at least 423 large cities (that is, with more than 300,000 people) across the globe are nestled inside 36 biodiversity hotspots: regions that harbor a high diversity of animal and plant species found virtually nowhere else in the world. And considering the growth trajectory of these cities—as modeled by the Seto Lab at Yale University—a staggering 90 percent of them could end up destroying the natural habitats of endangered species over the next decade or so.

That’s the conclusion of a study presented this week at the World Urban Forum in Kuala Lumpur by researchers from the University of Pennsylvania. Landscape architect Richard Weller, who led the study (but didn’t attend the forum), told CityLab by phone that this should be a wake-up call to rethink how to grow a city—especially since the deadline for Goal 11 of the U.N. Sustainability Development Goals, which spells out the need to integrate biodiversity into urban development agendas, will arrive soon, in 2020.

Atlas for the End of the World

Weller runs the project Atlas for the End of the World, which studies the intersection of urbanization and biodiversity. If the name itself doesn’t sound the alarm, the project’s series of maps detailing so-called conflict zones—where city edges may sprawl right into threatened habitat—will.

Using data from the Seto Lab, the researchers mapped the projected growth of those 423 cities over two other datasets: one covering areas with rapidly disappearing native plants; the other representing the home ranges of some 3,000 endangered or critically endangered mammal species. The team found that if 383 cities continue expanding as they do today, the result will be conflict zones.

In a second analysis, the researchers zoomed in on 33 “hotspot cities,” this time comparing the growth projections to the home ranges of non-marine animals. These cities are expected to experience the highest population growth and the most physical expansion in coming years, and Weller argues they should be top priority when it comes to saving biodiversity.

“What we’re arguing is the world needs to get these cities together to form an alliance,” he said. “They need to work together and share knowledge about their situations and help each other avoid this calamity.”

On the project website, maps of the 33 cities paint a detailed and desperate picture of how much land lies in the path of destruction, even with the expansion of just one city. Jakarta, Indonesia, for example, has long been on environmentalists’ radar for its chaotic urban sprawl and inadequate effort toward conservation and preventing climate change.

A map of projected urban growth for Jakarta, Indonesia, showing in red where the edges of the city overlap biodiverse areas. (Atlas for the End of the World)

By 2030, Jakarta is likely to add another 3 million to its population, and the edges of the city will be pushed farther out. The city lies in the Sundaland hotspot in Southeast Asia, whose species are already threatened by aggressive—and often illegal—clearing of forest for rubber and palm-oil production and by poaching, as well as by road construction.

The red areas represent urban/natural conflict zones; the darker the shade, the more likely that the land will be impacted. Light green areas represent protected areas and dark green shades indicate peri-urban zones harboring rich ecosystems.

This effort isn’t about prioritizing wildlife over humans, Weller said: “Cities have a membrane around them, this kind of no-man’s-land that’s actually got a lot of potential, because the city can invest in it,” he said. Not only can healthy ecosystems provide cities with abundant natural resources, they can also mitigate droughts, floods, and other effects of climate change.

A map of projected urban growth for Lagos, Nigeria, showing in red where the edges of the city overlap biodiverse areas. (Atlas for the End of the World)

A good handful of the hotspot cities are in developing countries—and their growth involves factors uncommon in the U.S. “A lot of the so-called sprawl is [the result] of people coming from rural landscapes into cities who can’t afford to live anywhere but in the peri-urban regions,” Weller said. “We’re expecting billions of people to live in those sorts of informal settlements this century, and that’s a problem, because they’re building their own city up there without any regulations.”

Fast-growing Lagos, Nigeria, developed much of its land by filling in swamps and destroying mangroves and wetlands, natural barriers to flooding. Its population is highly vulnerable to sea-level rise, especially on the outskirts of the city, in settlements that have cropped up without formal planning. The population of Lagos is expected to triple by 2050, which means that many more people will live in such areas, disrupting the habitats of aquatic and other species. (The government’s attempts to correct for its original lack of planning have proved disastrous, however, ending in mass displacement and violence.)

A map of projected urban growth for Los Angeles, California, showing in red where the edges of the city overlap biodiverse areas. (Atlas for the End of the World)

Weller said his team tries to “take a reading of each city, in terms of its self-consciousness about its environmental situation vis-a-vis biodiversity,” and for most, “there’s no documentation of significant planning or design efforts to avoid this calamity happening.”

Some cities are certainly more conscious than others—at least about combatting sprawl. Los Angeles, for example, has recently been able to densify thanks in part to transit improvements and ordinances that encourage developers to build more densely. But as the map above shows, that hasn’t eliminated potential conflict zones.

Urban design can help when it comes to negotiating with city planners and developers about how a city can grow. Perhaps, said Weller, urban designers can help explore ways to build for higher density, or convince developers to build away from areas with high biodiversity.

The problem with how we think about cities, Weller said, is that “we tend to ignore the periphery and be obsessed with the center.” But we can change our perception of what cities are. “At least in my field, in the 21st century, we’re beginning to understand cities as ecosystems,” said Weller. “And as nature, rather than something that is opposed to nature.”

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