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University of Arizona researchers unveil new model for desert farming in warming world

Caleb Ortega, an environmental studies undergrad student, harvests basil from an experimental garden outside Biosphere 2. Record heat has given the research new urgency. / Josh Galemore

In the cool shade of solar panels at Biosphere 2, a lush plot of herbs and vegetables hints at one possible future for farming in the desert.

At the moment, that future includes more basil than researchers know what to do with.

“We’ve been pulling out pounds of it every week,” said University of Arizona biogeographer Greg Barron-Gafford. “All of us are getting a little sick of pesto and pizza and mozzarella at this point.”

The experimental garden about 35 miles north of Tucson is part of a wider effort to radically reshape desert food production to meet the growing challenges posed by climate change.

A team of scientists, led by the University of Arizona, has developed a new blueprint for arid-land agriculture using wild, native crops and modern growing techniques.

The 14 researchers from the Southwest and Mexico believe their model can produce a sustainable, local source of food that will improve the health and well-being of consumers and farmworkers alike.

The idea involves a mix of desert-adapted food species grown cooperatively in ways that increase yield while reducing water use.

Along with all the basil, the current crop includes heirloom cherry tomatoes, Anasazi red beans and a special type of bell pepper brought in from Mexico. / Josh Galemore

The goal is healthy plants and people

Picture a variety of agave and fruit-bearing cactus interspersed with rows of mesquite and other legume trees, all with wild herbs, greens, beans and native chiltepin peppers growing in the shade beneath them. Other potential crops include squashes, mints and jicama.

In some cases, those plants would be grown beneath a photovoltaic “canopy,” as the solar panels generate cheap, renewable electricity to pump irrigation water and power farm equipment.

Pilot projects to test the model are now underway in the U.S. and Mexico, including at Biosphere 2 and in campus gardens at three public schools across Southern Arizona.

“I like to think of it as using the desert and the sun here as our laboratory for the future,” said Erin Riordan, a UA research associate and one of the lead authors on the paper.

The team focused on desert plants that are as nutritious as they are drought-tolerant, with special emphasis on crops that can reduce or even prevent diabetes and other chronic diseases often exacerbated by heat stress.

Meanwhile, the shady design of the growing areas would benefit both the plants and the workers tending to them, curbing the frequency of injuries or illnesses associated with farm labor in extreme environments.

Greg Barron-Gafford, Caleb Ortega and Alyssa Salazar work in a garden that is part of an experiment on growing techniques for hotter and drier desert conditions. / Josh Galemore

New ideas rooted in ancient expertise

The sweeping proposal, published recently in the journal Plants, People, Planet, is rooted in practices perfected over millennia by indigenous desert cultures.

“People have been growing food in the shade for 4,000 years in this region,” Barron-Gafford said.

“It’s not something that’s new to anyone,” added Gary Paul Nabhan, the study’s other lead author and a research social scientist in the university’s Southwest Center. “We’re drawing on that expertise and combining it with modern techniques and technology.”

The importance of food security has been highlighted in recent months by record-setting heat, sputtering monsoon conditions and supply disruptions caused by the pandemic.

“We are already hitting the temperature limits of conventional crops,” said Nabhan, a MacArthur award-winning agroecologist and the endowed chair in food and water security at UA.

Among the Southwestern farm staples most threatened by global warming, he lists corn, dry beans, melons, chiles and most vegetables.

“Yes, we can still grow chiles in our backyards,” he said, but growing them in a large-scale agricultural setting will become increasingly difficult as temperatures rise, droughts deepen and water resources shrink.

Nabhan added that a market already exists for some of the new crops considered in the study. “They’re already in our grocery stores, but we’re importing them from a thousand miles away,” he said.

Some plants have it made in the shade

Back at his outdoor laboratory at Biosphere 2, Barron-Gafford said pairing agriculture directly with solar generation could “open the door to food production in marginal lands” by providing both a shady place to grow plants and the electricity needed to pump water to them.

For the right crops, the shade beneath the solar panels can produce healthier, more productive plants with as little as half the water, all while extending the length of the growing season.

In turn, the plants provide a benefit to the solar array, cooling the air around it by as much as 12 degrees and improving the efficiency of the panels.

Barron-Gafford said the experiment in so-called “agrivoltaics” began nine years ago with a few plants tucked underneath a single, small solar panel slanting up from the ground.

“We started with salsa plants because we’re here,” he said with a smile.

The test garden now covers an area roughly the size of a half-court in basketball, shaded by a solar array mounted 10 feet off the ground.

Along with all the basil, the current crop includes heirloom cherry tomatoes, Anasazi red beans and a special type of bell pepper Barron-Gafford said was brought in from Mexico by the chefs at Penca restaurant downtown.

In a nearby control garden, equal-sized plots of the same plants bake in the direct sun. The basil there doesn’t even look like the same species. Its leaves are skinnier and more pointed, and the plants are already going to seed. One patch has shrunk and dried out in the heat, after its water ration was cut in half to match a similar plot still going strong in the shade of the solar array.

“Those plants died for science,” said Barron-Gafford, an associate professor with the UA’s School of Geography, Development and Environment.

Greg Barron-Gafford, a biogeographer associate professor at the University of Arizona, and Alyssa Salazar, a research assistant and senior studying physical geography, weigh crops from a garden outside Biosphere 2, on Sept. 10, 2020. The gardens are part of an experiment on new crops and growing techniques for hotter, drier desert conditions expected as a result of climate change. This includes looking at the differences between full exposure gardening, utilizing shade of solar panels and various ranges of watering. / Josh Galemore

Prepping for fall planting and the “big shift’

In a few weeks, he and his research assistants will plant a fall crop — both in the shade and out — of cilantro, fava beans, white onions and native mouse melons, which taste like cucumbers but look like miniature watermelons.

Agrivoltaic farming doesn’t work for everything. Broccoli, for example, tends to grow large, impressive leaves in the shade, but it never produces florets.

The jury is still out on the Anasazi beans. Barron-Gafford said the ones planted in the direct sun of the control garden have already produced their crop of seed pods, while the ones shaded by the solar array are taking their sweet time.

Whether that will lead to a fuller, more flavorful bean or a pile of tiny, underdeveloped pods remains to be seen.

There’s one thing the research team already knows: Transforming an entire agricultural sector won’t be easy.

“It is a big shift,” said Riordan, the principal scientist coordinating the bi-national research team based at the UA’s Desert Laboratory on Tumamoc Hill. “There’s a huge scaling piece that is going to have to be addressed.”

Change is coming, ready or not

One key part will be convincing consumers to expand their palates to include wild, locally grown foods they might not have considered before.

Luckily, Riordan said, Tucson already has something of a head start there, thanks to its diverse population, rich cultural history and its designation six years ago as the first UNESCO City of Gastronomy in the U.S.

The community is already home to about 40 startup businesses that produce more than 120 new desert food and beverage products.

Ultimately, researchers argue, desert agriculture will be transformed by climate change whether we want it to be or not. Through careful planning and adaptation, we can make that transition profitable instead of painful.

“It might be hard right now to envision edible desert landscapes, but it might not seem so far-fetched in a few years,” Riordan said. “I think we’re going to have a lot of motivation to come up with big solutions fast.”


Story by Henry Brean, Arizona Daily Star

Photos by: Josh Galemore, Arizona Daily Star

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