Nestled in New York City’s Greenwich Village, Public School 41 differs from its neighboring buildings in a way that’s both profound and only visible from above. Unlike the flat, gray roofs adorning other structures on the street, the school’s roof is a bright, verdant green. Covered in native plants, the vegetation provides an unlikely urban haven for birds and insects. It also acts as a natural stormwater control system and reduces the building’s carbon footprint. When the school’s students were asked how the roof made them feel, they said “free.”
Public School 41 is one of Michael Treglia’s favorite examples of New York City’s hundreds of green roofs. Treglia works for the Nature Conservancy as the lead scientist of the New York State Cities Program and is the first author of a 2022 paper published in Ecology & Security that used aerial data from 2016 to find 738 of the more than one million rooftops in the city are green.
Obviously, the city doesn’t seem to be taking advantage of all the thousands of acres of rooftops to make urban green spaces. But Treglia’s research also hints that we’re at the start of something new. The study is based on 7-year-old data, and Treglia’s more recent work suggests the number of green roofs is expanding.
“This is a growing industry,” Treglia tells Inverse. “In New York City and in a lot of parts of the country we’re still in the early adoption phase.”
This adoption can do more than ornament a city with plant life. Regreening cities has an extreme effect on the welfare of beings — particularly people. For example, studies show a link between being around nature and longevity: Urban dwellers live longer in neighborhoods with more trees and when they live closer to green spaces. Close proximity to nature is also linked to better mental health, a stronger immune system, improved pregnancy outcomes, and a reduction in cardiovascular disease.
The good news for city slickers is that they don’t have to go to the countryside to experience these perks. They can convert their urban jungle into a wild space.
Where urbanity and nature meet
A green roof on the Solaire apartment building at 20 River Terrace, which is in the TriBeCa neighborhood of Manhattan.
New York Daily News Archive/New York Daily News/Getty Images
Green roofs are part of a contemporary design movement to integrate nature into cities. This kind of biophilic urban design has varying terminology attached to it, but the principles underscoring the movement are clear: Nature benefits human health and well-being, and investment in nature protects a life-supporting system. Ultimately, we can build environments that combat climate change, support biodiversity, and make city dwellers happier and healthier.
Biophilia means a “love for our living systems” and design that supports biophilia takes this meaning to the extreme. For example, green roofs do not mean topping buildings with potted plants: They are the result of several layers intentionally constructed on top of a building, including the final detail of vegetation grown in soil. Among its many benefits, this living system can decrease the effects of air pollution, reduce the building’s energy use, and mitigate the urban heat island effect (the higher temperatures experienced in cities that compromise health).
The High Line Park is a popular tourist destination in New York, but it also serves as a welcome green space for New York City residents — both human and animal.
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But green roofs alone can’t solve for urban health and well-being. To strengthen the long-term resilience of cities and the people who live in them, Treglia and other experts argue we need to take a multi-pronged approach.
“We really need to think about all the aspects of a landscape,” says Treglia.
This could mean planting and managing trees along streets, installing vertical hanging gardens on walls, or embracing urban rewilding. The latter is especially gaining momentum, explains Steffen Lehmann, a professor at the University of Nevada, Las Vegas, and an expert in sustainable architecture.
Rewilding refers to restoring an area of land to its natural uncultivated and self-regulated state. It’s been a strategy of the conversation movement for a few decades, especially in the restoration of large wilderness areas. But now rewilding is trickling into urban spaces — the reintroduction of native flora to parks and yards, for example, or removing man-made barriers from natural stream systems.
“It is a shift away from a centuries-long tradition of managing and controlling public green spaces, heavily manicured lawns, and using pesticides,” Lehmann says.
Bishan-Ang Mo Kio Park has become a city haven for Singaporeans.
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In practice, rewilding at home could look like converting private gardens into meadow-like spaces that provide nectar and pollen for bees and butterflies. The High Line in New York City, Singapore’s Bishan-Ang Mo Kio Park, and London’s Thames21 project are all examples of city-level rewilding in action.
These spaces absorb and sequester carbon dioxide emissions, support wildlife, and improve a city’s livability. In these ways, Lehmann sees rewilding as “much more effective than a standard green roof,” like the residential buildings topped with plots of succulents or Kentucky bluegrass. Green roofs that are planted with native flora and allowed to grow into wild spaces are, so the theory goes, more beneficial to our health and happiness in the long run.
Some of the most exciting biophilic urban design projects incorporate multiple elements. For Lehmann, the Berlin Tempelhofer Feld stands out. After the Tempelhofer Airport was closed in 2008, the city of Berlin reclaimed the space. Two years later, it opened as a public park with trails, urban gardening, and a large rewilding area. It’s the largest inner-city open space in the world.
The cost of going green
Berlin’s Tempelhofer Feld public park was once an airport, but now it provides a green space for people to gather and relax inside the city.
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Nature-based design solutions to city problems are becoming more popular, thanks to recent laws encouraging solar and green roof builds, influential city projects taking a lead, and a new class of green designers all working toward a goal of making cities beautiful and healthier. But there remains the question of whether or not all city-dwellers experience these nature-derived benefits equally. Multiple studies show that poorer neighborhoods experience hotter temperatures and poorer health outcomes as a result. In Treglia’s study on New York City’s green roofs, most appeared to be clustered in high-income neighborhoods, like midtown and downtown Manhattan. Social dynamics like wealth and location might ultimately filter who gets to benefit from green roofs, Treglia says.
“Are green roofs meaningfully expanding into areas that have historically not had them,” Treglia asks, “or are they in the same places as before? If these spaces are really going to benefit people, they need to be accessible in a way that’s equitable.”
People pay a premium to access green roofs, Treglia observes. They often beautify commercial spaces and expensive residential buildings — places typically closed to the public. The rooftop garden above Radio City Music Hall may be idyllic, for example, but most New Yorkers will never see it.
This green roof, atop a USPS building in midtown Manhattan, benefits the building and the city — but members of the public are unlikely to ever see it.
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Expanding nature in urban settings will take time, money, and a change of thinking. Some of the barriers are real — there are not many organizations that install green roofs, Treglia says — but others are perceived. You might know that the fancy building up the block has a roof garden, but you might not know that your own building could support a similar (if not better) green space. And though green roofs come with a cost upfront, studies suggest the benefits outweigh the initial investments.
Cities can, in turn, transform underutilized spaces or nurture reclaimed spaces. Nature, then, becomes not just a design choice, but a way to sustain life.
“We are just at the beginning of understanding the full potential,” says Treglia.
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