You may not have noticed, but a butterfly or bee certainly has. It is a strip of dirt and grass between a sidewalk and a street, or an empty lot, or green that runs along a railway line. Compared to an official city park, these “informal green spaces” don’t get much love from people, even though they serve as invaluable sanctuaries for pollinators and other urban species.
“They are the kind of forgotten, unthought of places, unplanned spaces,” said Hugh Stanford, an urban sustainability researcher at RMIT University in Australia. “You feel like you’re in some kind of secret wilderness. For all intents and purposes they provide an environmental benefit but are completely overlooked by formal planning bodies.”
Just as an impromptu hangout can be as fun as a formal gala, even an unplanned green space can offer the benefits you’d get from an official park: they support biodiversity, their trash can soak up rainwater to prevent flooding, and they release water vapor to cool the surrounding area. Stanford’s new research finds that they also get a surprising amount of engagement from human passers-by, suggesting that informal green spaces improve mental health by reuniting urban populations—which is explode worldwide — with nature. And promoting them can be especially impactful in underserved neighborhoods without formal green spaces.
Stanford and his colleagues zoomed in on Greater Melbourne, Australia, using land use data to identify green spaces. They sorted the formal plots, such as proper parks and residential gardens, from the rest of the informal green spaces. The team then married that mapping with anonymized data from citizen science apps like iNaturalist, which showed where in Melbourne people stopped to interact with nature — to identify a plant or insect. “People use informal green spaces about as much as they use formal green spaces—we really couldn’t tell the difference between the two,” says Stanford, lead author of a new paper describe the findings. “But that’s not an excuse for planners to come along and say, ‘Oh, well, people use railroads, and let’s just get rid of all the parks.’
The team found particularly strong engagement with green around railways and utility infrastructure. This may be because those areas have been left to grow over longer periods of time. Compared to a lawn in a city park that is constantly shredded by a lawnmower, species in an informal space come and go with the seasons: Flowers bloom, attract pollinators and feed herbivores.
“That means you can get some interesting ecological emergence and spontaneous growth of vegetation,” Stanford said. “You get quite important biodiversity on these sites, including endangered species. What might be considered a weed to some might be considered an urban oasis to others—certainly for birds.” Native pollinators also love a good mess of greenery, both for food and for protection: In a wide open field there is nowhere for them to hide from predators.
Beyond Melbourne, other researchers have also begun to quantify these unmanaged green spaces. In 2019, scientists scoured satellite images of two neighborhoods in Philadelphia – South Kensington and Olde Kensington – and then walked each block to confirm patches of green. They 351 green spaces found, a total area of 1 million square feet, of which more than two-thirds was informal. (Think of all the unused land that stretches under high-voltage power lines.)
“These are things that the city may not necessarily be aware of,” said Illinois State University urban geographer Alec Foster, who conducted the research. “So to think about how these green spaces might provide opportunities for people to use them who might not otherwise have access to a park.”
Nurturing these spaces sometimes means just letting them grow wild, undisturbed. In other cases, a city can turn vacant lots into community gardens, providing both food for people and habitats for animals. Community members can also tend smaller roadside plots by using cues such as small fences or signs to telegraph to pedestrians that the area is under active management.
In underserved neighborhoods, where city governments have not invested in parks, informal green spaces can provide much-needed refuges for people to engage with nature. But Foster cautions, cities shouldn’t do this kind of rehab without community input on what residents actually want for their neighborhood — say, a garden versus a more recreational park on an empty lot.
And just as city employees are paid to maintain formal parks, so too can a government employ local residents to maintain informal green spaces. “Retired people who could use a part-time job, with a little investment in seeds and tools, they can really care for and love a space,” says Elizabeth Sawin, director of the Multisolving Institute, which advocates solutions that address multiple problems at once. solve “Or you have young people where it’s a career path to learn about horticulture and maintenance and planting trees.”
As more and more people flock to cities around the world, informal green spaces will be increasingly critical to maintaining that connection with nature. “Everybody has this very complicated relationship with versions of this phenomenon in their life,” Stanford said. “The fact that people use informal green spaces, at least to me, suggests that there is something special about them that is not provided by other formal green spaces.”
