Near downtown Tucson, Arizona, is Dunbar Spring, a neighborhood unlike any other in the city. The unpaved sidewalks are lined with native, food-bearing trees and shrubs fed by rainwater diverted from city streets. One single block has over 100 plant species, including native goji berries, desert ironwood with edamame-like seeds and chuparosa bushes with cucumber-flavored flowers.
This urban food forest – which began almost 30 years ago – provides food for residents and roughage for livestock, and the tree canopy also provides relief to residents in the third-fastest warming city in the nation. It has made Dunbar Spring a model for other areas grappling with increased heat, drought and food insecurity caused by the climate crisis.
“We’re creating a living pantry,” said Brad Lancaster, a resident and co-founder of the Dunbar/Spring Neighborhood Foresters organization, which planted the urban food forest.
Dunbar Spring’s urban food forest began on an early morning in September 1996, when residents gathered for the first-ever community-wide tree-planting event. Like many lower-income areas in Tucson, Dunbar Spring was unusually hot, lacking the street tree cover to provide shade during the city’s brutal summers. Temperatures today are 4.5F warmer than in the 1970s.
The plan, headed up by Lancaster, was to plant multi-use drought-tolerant shade trees in streetside basins that could capture rainwater and create “a more livable community”, he said.
Almost 30 years later, neighborhood foresters have planted more than 1,700 trees and thousands more understory plants, transforming Dunbar Spring into an urban food forest fed by rainwater.
“We can plant resilient native trees that are not dependent on imported water for irrigation,” said Lancaster, standing near a series of curb cuts that pull storm water off the street into sidewalk plantings. “Trees shade the street, reduce heat stress and provide food for our neighborhood.”
Before the pandemic, Dunbar Spring held annual community-wide milling events, in which pods harvested from the hundreds of mesquite trees in the neighborhood were ground into flour – giving them a year’s supply of flour, according to Lancaster.
The work in Dunbar Spring, along with Lancaster’s books and website, have inspired people worldwide to take up water harvesting to irrigate native food-bearing street trees. “In almost every neighborhood in Tucson, you can now find at least one property doing this,” he said.
Sonya Norman is one of them. Inspired by Lancaster’s work, Norman began organizing tree planting and water harvesting events in her neighborhood of Blenman-Elm, east of Dunbar Spring. She started by planting mesquite and palo verde trees along her children’s walking route to elementary school.
This evolved into simple water harvesting – what Lancaster calls “planting the rain” – by using gravity and curb cuts to direct water from paved surfaces into planted streetside basins that capture water.
The work of Dunbar Spring neighborhood foresters has also informed Tucson’s climate action plan, including legalizing citywide rainwater harvesting and planting arid-adapted trees. Fatima Luna, the city of Tucson’s climate and sustainability adviser, said Dunbar Spring demonstrates how storm water harvesting can be implemented at the neighborhood scale “using low-tech, low-cost technologies that direct runoff into vegetated basins where it infiltrates the soil and supports native vegetation”.
And Tucson’s mayor, Regina Romero, launched Tucson Million Trees in 2020, an initiative to plant 1m drought-tolerant shade trees to help mitigate the impact of climate change.
On a cloudy Saturday in January, Katie Gannon, arborist and program manager for Tucson Million Trees, gathered with program staff and volunteers in the A Mountain neighborhood for a tree-planting event. The goal that day was to plant 97 desert-adapted shade trees, including pomegranate and fig trees, outside three dozen homes – which would provide food and cooling shade to residents.
“Heat is an equity issue. It affects different populations differently,” Gannon said. “When we talk about heat-vulnerable neighborhoods, this is the type of neighborhood we are especially keen on getting into.”
“If climate change continues at its current pace, cities in the south-west such as Tucson could experience as much as 45 days more per year with temperatures above 90F [32C] by 2100,” said Ladd Keith, an assistant professor at the University of Arizona working at the intersection of urban planning and climate change.
A Mountain resident Eris Escalante chose a desert willow and a drought-tolerant oak for her backyard. She hopes the trees will make summers more bearable for her pet tortoise and exotic birds.
“Summer is just too hot. I think the trees are really going to help,” she said.
Shade can have a profound effect on urban neighborhoods. One day in September, the temperature on an exposed street in Dunbar Spring was 123F (50C), while a shaded street was just 85F (30C) – a 38F (20C) difference.
On rainy days, Dunbar Spring looks completely different. First Avenue, which runs through the entire neighborhood, transforms into a rushing stream, filling streetside basins, planted roundabouts and other earthworks with water. These water management practices, Lancaster said, are rooted in Indigenous rainwater harvesting techniques, in particular Ak-Chin runoff farming, practiced in the Sonoran desert for millennia.
For Lancaster, city streets hold vast, untapped potential. One mile of road in Tucson drains over a million gallons of storm water runoff a year, enough to support 400 native food-bearing trees, said Lancaster.
These practices will become increasingly important as the US south-west continues in its historic megadrought, and many cities, including Tucson, rely on imported water from the declining Colorado river. “The majority of the water that irrigates landscapes in Arizona is not indigenous water,” said Lancaster, as he walked east toward the now-dry Santa Cruz River, depleted for decades through overuse.
These time-tested water harvesting techniques, coupled with climate-smart desert food production, will be crucial in building food security in the warming south-west, especially as agriculture consumes 74% of Arizona’s fresh water.
“Part of the tragedy is we have not valued the Indigenous knowledge of this place,” said Lancaster.
For Lancaster, surviving and thriving in an increasingly hot and dry world will require dramatic and necessary changes to how we live. “We need to adapt ourselves and our practices in a way that doesn’t just serve us but the living systems that allow us to be here,” he said.