Urban agriculture, the practice of farming within the limits of a city, is becoming increasingly popular around the world. Once a hobby for a few people, it now produces one-fifth of the world’s food — and it does so without harming the natural world. In fact, according to a new study, urban gardens also have a positive effect on the overall wellbeing of the people who care for them.

Urban gardens are an interesting trend. Having access to fresh produce you can grow yourself is one part of it, but perhaps an even more important part is being able to re-green a part of the city, and research has shown that green spaces, even small green spaces, can have a positive effect on our minds and bodies.

Researchers from the University of Texas at Austin wanted to see just how much of a benefit green gardens provide. They looked at almost 30 urban community gardens across the state of California over five years and quantified biodiversity and ecosystem functions, such as pollination, food production, pest control, and human well-being. They found benefits across the board in the gardens.

“We wanted to determine if there were any tradeoffs in terms of biodiversity or impacts on ecosystem function,” Shalene Jha, study author, said in a statement. “What we found is that these gardens, which are providing nutritional resources and well-being for gardeners, are also supporting incredibly high levels of biodiversity.”

Why urban gardens are important

While the relevance of urban gardens has been highlighted by previous studies, this is the first one to look at their effects across a wide range of biodiversity measures and ecological services. They are ideal systems for exploring the mechanisms underlying trade-offs and synergies in biodiversity and ecosystem services, the researchers said.

For their study, they collected data from 28 urban gardens on the central coast of California between 2013 and 2017. The researchers visited the gardens three to five times from May to September and evaluated their biodiversity, from plant species richness to ground cover composition. They also measured seven ecosystem services.

They found multiple synergies and only a few trade-offs in the urban gardens; in other words, urban gardens help biodiversity and synergize with it. This contrasts with previous assumptions that food production is always at odds with biodiversity, almost entirely based on intensive rural agriculture enterprises, and shows that urban gardens are very important habitats where synergies dominate, they said.

The researchers also found that the choices that gardeners make can have a big impact on their local ecosystem. Planting trees outside crop beds could increase carbon sequestration without limiting pollinators or lowering food production from too much shade. Also, mulching only with crop beds could improve soil carbon services without affecting pollinators.

“It’s estimated that by 2030, about 60% of the world’s population will live in cities,” Jha said. “And urban farms and gardens currently provide about 15%-20% of our food supply, so they are essential in addressing food inequality challenges. What we’re seeing is that urban gardens present a critical opportunity to both support biodiversity and food production.”

Over 55% of the world’s population, 4.4 billion inhabitants, currently live in cities. This trend is expected to continue, with the urban population expected to double by 2050, at which point seven out of ten people will live in cities. Urban gardens could make a big difference, supporting local food production and improving ecosystem services.

The study was published in the journal Ecology Letters.