Urban farms can make cities more livable and help feed America

If you've ever spent time on a roof, you know that it's not particularly pleasant – the sun is scorching in the summer, cold and windy in the winter. However, if you put several solar panels there, the calculation changes: shaded from gusts of wind and excessive sunlight, crops can multiplya method known as rooftop agrivoltaics. And because this equipment provides shade, evaporation is reduced, resulting in significant water savings. Plus, all that greenery insulates the top floor, reducing energy costs.

Urban areas, long at odds with each other, are embracing elements of the rural world, trying to produce more food for themselves in community gardens on the ground and agrivoltaics above. In an increasingly chaotic climate, urban agriculture could improve food security, produce clean electricity, reduce local temperatures, provide shelter for pollinators, And improve the mental and physical health of citizensamong other benefits.

Thanks to relatively cheap investments in food production – especially if there are empty lots around – cities can solve a lot of problems at once. For example, Quezon City in the Philippines. converted unused land in over 300 gardens and 10 farms, while training over 4,000 urban farmers. Detroit is speckled thousands of gardens and farms. Non-profit organization in the Big Apple Project Lepestki transforms empty lots in poor areas into oases. “There are places in New York City where there isn’t a single green space for 5 miles,” said Alicia White, the group’s executive director and founder. “And we know that green space helps reduce stress. We know that it helps combat loneliness, and so far we know that it helps improve our respiratory and heart health.”

This makes these public spaces a particularly effective climate solution as people in cities find it increasingly difficult to stay healthy due to the urban heat island effect, in which the built environment absorbs solar energy and releases it during the night. Baking day after day during prolonged heat, the human body cannot get relief, which is especially dangerous for older people. But green areas lower temperatures by releasing water vapor (essentially sweating air) and providing shade. At the same time, as climate change leads to increased rainfall, urban gardens help absorb floodwaters, reducing the risk of flooding.

Ironically, although the furnace effect is dangerous for people, it can benefit urban farms. On rooftops, scientists are finding that some crops, such as leafy greens, thrive in the shade of solar panels, but others—especially warm-season crops like squash and watermelon—thrive in the harsh conditions of full sun. “Most of our high-value crops benefit from the urban heat island effect because it extends their growing season. So growing food in the city actually makes sense,” said horticulturist Jennifer Bousselot, who studies rooftop agrovoltaics at Colorado State University. “This summer we had cucumbers the size of baseball bats that fit perfectly on the green roof.”

That's not all that's thriving there. Bousselo and her team also grow three native crops: corn, beans and squash. The beans climb the corn stalks and the microbes in their roots fix nitrogen, enriching the soil, while the squash leaves shade the soil and reduce evaporation, conserving water. They also found that saffron, an extremely expensive and hard-to-find spice, tolerates the shade of rooftop solar panels well. Water coming out of the soil also cools the panels. increasing their efficiency. “Essentially, we are creating a microclimate very similar to a greenhouse, which is one of the most optimal conditions for the growth of most of our food crops,” Bousselot said. “But it’s not a system that needs heating, cooling or ventilation like a greenhouse.”

Manufacturers can even use extreme rooftop conditions to gain another benefit. Plants that are not shaded by solar panels produce “secondary metabolites” in response to heat, wind and constant sunlight, which can stress them. These are often antioxidants that the manufacturer could obtain from a medicinal plant such as chamomile—at least in theory. “We're kind of exploring the breadth of what's possible there,” Bousselot said, “and using that unique environment to produce crops that we hope will be even more valuable to the grower.”

In New York, the Petals Project has seen similar success. While agricultural regions cultivate vast fields and orchards of monocultures such as grains or fruit trees, an urban farm can fit a bunch of different produce into a limited space. “If you could grow it in the countryside, you could grow it in the city,” White said. “We grew pumpkins, peas, lemongrass. I saw almost everything in our gardens.”

This diversification means that a cornucopia of nutritious foods are brought into the community. (Many different species also provide pollinators with different kinds of flowers—and the more pollinators, the better the crops and native plants in the area can reproduce, creating a virtuous cycle.) This is invaluable because access to good food is extremely unequal in the United States: in Mississippi, for example 30 percent of people live in low-income neighborhoods with limited access to good food, compared with 4 percent in New York City. This results in “silent hunger,” in which people have access to enough calories (often from ultra-processed foods bought at corner stores) but do not have enough nutrients.

Of course, low-income areas need better access to supermarkets, but rooftop gardens and community gardens can provide fresh food and help people improve their diets. “It’s not just about growing your own vegetables in the city, but also a hook for changing habits,” said Nicolas Galli, a researcher studying urban agriculture at the Politecnico di Milano.

IN study Published last month in Earth's Future, Galli modeled what this change might look like on a large scale in Sao Paulo, Brazil. In a theoretical scenario in which the city turned its open space—about 14 square miles—into gardens and farms, every couple of acres of food production could provide healthy meals for more than 600 people. While that scenario isn't particularly realistic given the scale of the changes needed, “it's interesting to think that if we used more or less all the space we have, we could provide the missing fruits and vegetables to 13 to 21 percent of the city's population,” Galli said. “Every square foot you make can have a function, can be useful in increasing access to healthy food for someone.”

Without urgent action, silent hunger will only get worse as urban populations grow around the world: by 2050 70 percent of people will live in cities. Urban farms could go a long way in feeding all these people and could really benefit from rural farmers moving to metropolitan areas. “They can pass that on to community members like me in New York who may not have had the experience,” White said, “and help them find their way in learning to garden and grow their own food.”

The urban garden, whether on a rooftop or between apartment buildings, is a simple yet uniquely powerful tool for addressing a variety of environmental and human health issues. “They serve as a space where people can grow, where they can learn and where they can help fight climate change,” White said. “It’s really nice to see that people are starting to wake up to the fact that a garden and green space can actually have a bigger impact than just this community as a whole.”