Traditionally, growing food was thought to result in a loss of biodiversity and negative impacts on an ecosystem. A new study by researchers from several universities, including the University of Texas at Austin, refutes this assumption, showing that community gardens and urban farms positively affect biodiversity, local ecosystems and the well-being of the people who work in them.
The study, published in Ecological Lettersspent five years studying 28 urban community gardens across California, quantifying plant and animal biodiversity and ecosystem functions such as pollination, carbon sequestration, food production, pest control and human well-being.
“We wanted to determine if there are any trade-offs in terms of biodiversity or impacts on ecosystem function,” said Shalene Jha, associate professor of integrative biology who was the lead author of the paper. “What we found is that these gardens, which provide tremendous food resources and increase gardener well-being, also support incredibly high biodiversity of plants and animals. It’s a win-win situation.”
Previous assumptions by scientists about the negative impact of food production on biodiversity were based almost exclusively on intensive rural farming operations, which tend to only grow one or two types of crops, often on a large scale. Urban community gardens, private gardens, and urban farms and orchards tend to grow more plant species in smaller areas. This new study is the first to examine the impact of urban gardens on a wide range of biodiversity policies and ecological services.
“It is estimated that by 2030 about 60% of the world’s population will be living in cities,” Jha said. “And urban farms and gardens currently provide about 15% to 20% of our food supply, so they are essential to addressing the challenges of food inequality. What we are seeing is that urban gardens represent a crucial opportunity to support both biodiversity and local food production.”
The study also found that the choices gardeners make can have a major impact on their local ecosystem. For example, planting trees outside of crop beds could increase carbon sequestration without restricting pollinators or reducing food production from too much shade. And mulching only within beds could help improve soil carbon services while avoiding negative impacts on pest control and pollinators.
The research was funded by the US Department of Agriculture’s National Institute of Food and Agriculture, the National Science Foundation, and grants from the University of California. Monika Egerer, Peter Bichier, Hamutahl Cohen, Stacy M. Philpott and Azucena Lucatero from UC Santa Cruz, Heidi Liere from Seattle University and Brenda Lin from CSIRO Land and Water Flagship in Australia were co-authors of the study.