people for a long time The competition between the city and the countryside has been triggered, and the culture and environment are very different. But a nascent movement — along with the field of science — is eroding that divide, bringing more of the country into the city. It’s called urbanization, and it promises to provide more locally grown food, beautify the built environment, and even lower temperatures during heat waves.
It also overturns long-held assumptions that growing food is directly bad for biodiversity because clearing land for agriculture requires the removal of native flora and fauna.The idea, says ecologist Shalene Jha of the University of Texas at Austin, is based on a study of countryside Agriculture, growing industrial tracts of corn or wheat can be disastrous for existing ecosystems. But that doesn’t apply to urban farms, gardens, or even smaller green spaces.
In a recent paper in the journal Ecological Express, Jha and her colleagues show that urban gardens can actually boost biodiversity—especially if residents prioritize planting native species, which attract native insects like bees. “In this case, the gardener actually has a lot of power,” Jha said. “The size of the garden doesn’t matter. It’s the practices of farming the landscape—and the decisions they make about vegetation and ground cover—that ultimately determine the biodiversity of flora and fauna there.”
Jha’s team characterized the biodiversity of 28 California urban gardens over a five-year period. Far from the monotony of wheat fields, they found rich ecosystems full of vitality, which in turn increased species diversity. The researchers identified predators like birds and ladybugs, which prey on insects that feed on crops and thus help yields, and pollinators, such as honeybees, that also benefit from crop diversity and Increased plant productivity. This means that urban gardens not only produce food for humans, but also provide food for other species. “They actually support incredibly high levels of plant and animal biodiversity,” Jha said.
This biodiversity is largely due to strategic trade-offs. One of the challenges of urban gardening is that it requires a lot of manual labor: you can’t drive a combine across the city during harvest time. But that restriction has proven to be an ecological blessing. Because everything is done by hand, urban farmers can plant various plants next to each other, squeezing them tightly together to increase yields.
In another study published this month in the journal sustainable agronomy, a separate research team studied 72 urban agricultural sites in France, Germany, Poland, the United Kingdom and the United States. “We see fairly diverse growing spaces, often with a wide variety of crops and non-food items,” said study author Jason Hawes, an environmental sustainability researcher at the University of Michigan. On average, these sites grew 20 different crops. “A lot of people also just have flowers in their visual gardens for fun, and community gardens have flowers too, to make the space more pleasant,” he said. “Those things really contribute to local biodiversity.”
