Ask a person on the street to talk about urban biodiversity (the number and abundance of plant and animal species) and they may mention pigeons, rats and maybe London plane trees or tulips. These are the cosmopolitan species found in cities throughout the world. The city’s equivalent of the domestic dog or cat. But the story doesn’t end there.
There are also numerous species living among us that can surprise and delight, including coyotes and a snowy owl in New York City’s Central Park, or the mountain lion, P-22, in Griffith Park in Los Angeles. Other wildlife has shown us how cleaning up the environment can make a difference. After poor water quality forced the harbor porpoises out of San Francisco Bay and otters from Marin County, Calif., for decades, both have returned. And in some cases, cities can provide a refuge from threats faced in non-urban areas.
With some exceptions, many cities are doing little to support the plants and animals living in their midst, yet many species can be found there anyway, and evidence suggests we could be doing more. Conservation efforts in cities could help protect species that are unique to cities, while also buttressing regional efforts to conserve species found more broadly in cities and their surrounding wildland areas. Biodiversity planning could focus on enhancing existing biodiversity supporting features, such as large parks and river corridors, and creating new ones where they are scarce. These actions would help species move across the urban landscape to access water and food, growing the number and abundance of species that urban settings could sustain.
But ultimately, we should conserve biodiversity in cities not just because it is good for conservation, but because it is also good for us. Biodiversity may help support a healthy microbiome in our guts and on our skin, which may provide protection against chronic conditions such as asthma and allergies. In a long-term and well-replicated study from New Zealand, children living in areas with a greater diversity of types of vegetation had lower odds of developing asthma when accounting for differences in economic background, education and other factors with a suspected link.
Biodiversity can make us feel good as well. For example, a recent summary of several studies showed that spending time in biodiverse spaces can reduce stress, anxiety and feelings of depression. And biodiverse soundscapes can also contribute to wellbeing; hearing birdsongs can reduce feelings of stress and annoyance. Furthermore, several studies have found that engaging with nature in our backyards through gardening can make us feel good, can help us feel more connected to our communities, and can contribute to our physical health by reducing body mass index.
We haven’t engineered cities to support biodiversity, but we could. As cities are retrofitted, scientists have pointed out that the need for climate adaptation provides a huge opportunity to incorporate actions for biodiversity. These can be as simple as selecting trees to line streets that will both support wildlife and be well-adapted to the future climate. Or they can be large and expensive, such as the acquisition of land to create new parks. But some of these more expensive actions can come along with other goals we’d like to achieve anyway, such as reducing inequity in access to nature by adding parks in neighborhoods where they are lacking. Making cities greener so they can support more biodiversity can be a winning strategy for supporting conservation, reducing social inequity and supporting human wellbeing.
Erica Spotswood, Ph.D., is the lead scientist for the Urban Nature Lab at the San Francisco Estuary Institute.