Science Is Revealing the Social Disparities at the Root of Urban Ecosystems

On a cloudy September morning in Prospect Park, a massive swath of greenery amid Brooklyn’s concrete sprawl, the fall migrants are flying fast and furious. A group of birders spin excitedly in a clearing, calling out as new species appear. “What a hotspot,” says Valentina Alaasam as she scribbles down each name in rapid succession: American Redstart, Scarlet Tanager, Black-and-white Warbler.

Alaasam will add the morning’s counts to a biodiversity database that she and her colleagues at New York University have been compiling for more than a year. The goal: to figure out whether parks in richer areas are also richer in wildlife. “I’ve always been really interested in this concept of luxury effects, where neighborhoods that are wealthier tend to get more investment from the city, and more trees, and more green spaces,” Alaasam says. To test how that may play out in New York, the team has been counting birds, bugs, frogs, and more across 11 city parks, including relatively well-maintained oases like Prospect Park and others that receive less upkeep.

The project will add to a growing body of research that’s revealing how economic and racial inequities shape urban ecosystems. In many cities, money has proven to be a major ecological boon: Wealthier neighborhoods host more of the street trees and park spaces that attract wildlife, while poorer areas have more uninterrupted concrete, leaving residents less likely to spot a flitting vireo or loping coyote. Yet such disparities didn’t pop up overnight, and in recent years, scientists have been peeling back the deeper layers that create these patchworks. “The injustices that have shaped what we are today—as a nation, as a society—are shaping the entirety of the planet,” says Christopher Schell, an urban ecologist at the University of California, Berkeley.

In 2020 Schell and his co-authors published an influential study suggesting that biodiversity in cities was strongly tied to systemic racism. In particular, they argued, discriminatory federal housing policies known as redlining, though long abandoned, still shape local ecology today. Starting in the 1930s, federal housing agencies graded neighborhoods to inform whether banks should offer loans there—and assigned lower grades to places where racial minorities lived. Residents in these areas, which were delineated in red ink to mark them as “hazardous,” were then less likely to receive mortgages or local funding and more likely to watch their neighborhoods get torn up by highways or saddled with toxic pollution. 

Though the practice was outlawed in 1968, that legacy of segregation and disinvestment still echoes through American cities. “They’re no longer graded,” says Chloé Schmidt, an evolutionary ecologist at the German Centre for Integrative Biodiversity Research who has researched the effects of U.S. redlining. “But those environmental differences persist.”

Studies across multiple cities have found that areas deemed most desirable on the color-coded maps are greener today: They have nearly twice as much tree cover as redlined areas and are home to a higher diversity of animal species. Bird surveys in Los Angeles have shown that forest birds such as warblers flock to more affluent areas, while historically redlined communities mainly host classic urban dwellers like pigeons and sparrows. Meanwhile, Schmidt’s work has found that animal populations in minority neighborhoods have lower genetic diversity, suggesting they’ve been fragmented by barriers like highways and may have more trouble adapting to environmental change.

Still, the patterns around wealth, segregation, and nature are not always simple, says Diego Ellis Soto, a conservation research fellow at UC Berkeley. His work has found that redlined areas tend to have far fewer bird observations in crowdsourced databases like eBird and iNaturalist. Scientists often use those tools to estimate biodiversity, so it’s possible they are overlooking species-rich hotspots. “In some of these redlined neighborhoods, we have so little data that we can’t even talk about what lives there,” he says.

Plus, the manicured habitats typical of areas deemed more desirable on old housing maps may even be less inviting for certain species, says Rafael Baez, a biology graduate student who is helping lead the New York project. Prospect Park is great for birds, but it’s Highbridge Park in Manhattan’s Washington Heights—a stretch of green along the largely Hispanic neighborhood, where Baez often finds park entrances blocked off and forest floor left untended—that offers the rich layers of leaf litter and rotting logs that salamanders love.

As the team teases out these threads, Baez and Alaasam hope their findings can help inform park management and conservation efforts in New York, whether it’s developing green spaces in areas that haven’t gotten their fair share or recognizing and protecting rich habitats that have flown under the radar. In cities around the country, reckoning with our unequal history will be crucial to solving the biodiversity crisis and building a better path forward for people and animals alike, scientists say. “We can’t just sweep everything under the rug,” Schell says. “We’ve got to face our past if we want to have a future.”

This piece originally ran in the Winter 2024 issue as “The Green Gap.” To receive our print magazine, become a member by making a donation today.