“I joke that this farm is a little better than Death Valley, but I’m not really joking,” said Yadi Wang, the farm director, as he drove his pickup through this 665-acre ranch about a two-hour drive from Phoenix.

For Wang, every day at the ranch is different. During the winter, he spends his days preparing fields of heritage wheat, planting seeds, and laying pipes from irrigation ditches to the row crops edging the now-dry Gila River. Early summer is the busiest, with the farm team spending up to 10 straight days harvesting the desert-hardy wheat, barley, and other grains.

“These cash crops translate into the tangible,” Wang said. Yet much of his time is devoted to a longer-term, less noticeable project: restoring degraded land, often through practices that originated with the Indigenous peoples of this region.

Oatman Flats Ranch is attempting to create a sustainable, scalable model for regenerative farming in the Southwest, demonstrating what can and perhaps should be grown in an increasingly hot, dry, and water-limited region. In 2021, Oatman Flats Ranch became the region’s first-ever Regenerative Organic Certified farm, with practices build soil health and biodiversity, help sequester carbon, and reduce water consumption. Now it’s been designated as a Regenerative Organic Learning Center by the Regenerative Organic Alliance (ROC), welcoming other farmers interested in observing and talking about the practices there.

‘We Need a Significant Change in How We Farm’

“If we’re going to hold on to farmland, we need a significant change in how we farm and what we farm,” said Dax Hansen, the ranch’s owner.

But it won’t be easy. Oatman Flats Ranch has undergone a dramatic transformation that required significant investments in training, research, equipment, and techniques, all of which took years to deliver a return. Although processes have been refined and problems worked out along the way, with insights that Hansen freely shares with other farmers, many practices are out of reach for the average farmer.

“It’s an experimental farm,” Wang said. “I have a lot of respect for [Hansen], willing to get all these cash assets to pour into this, to lose money. Not many people can or are willing to do that.”

Hansen, a successful financial technology lawyer who grew up in Mesa, Arizona, purchased the property from his aunt and uncle in late 2018. Oatman Flats Ranch has been in the family for four generations. His grandfather Ray Jud Hansen ran cattle in the 1950s before becoming one of Arizona’s first conventional cotton farmers.

The land was severely degraded when Hansen bought it, with compacted, salty, eroded fields caused by decades of conventional farming practices and 10 years of neglect. The soil was more than 55 percent clay. “It was pretty bleak,” Hansen said. “[The land] had basically been sterilized, with almost nothing growing on it.”

Hansen wanted to demonstrate the potential for regenerative farming in the arid Southwest, so he and his team redesigned the farm. They began by restoring the dilapidated infrastructure, repairing wells and pump equipment, excavating irrigation ditches, and purchasing the necessary farm equipment. They cleared hundreds of invasive trees, leveled the fields, fertilized them with manure, and planted cover crops to improve soil and water quality. In addition, Hansen commissioned an ethnobotany and archaeology study of the property to understand what crops had historically been planted at Oatman Flats Ranch.

Meanwhile, the neighboring farmers no longer grow food for people; their crops provide feed and fuel. Oatman Flats Ranch is surrounded by millions of acres of alfalfa for livestock and corn for ethanol, watered by one of the world’s fastest-draining aquifers.

“Climate change and a persistent megadrought are reducing the flow of rivers in the West, yet we have been unable to sufficiently reduce our dependence on these rivers to keep demands balanced with supplies,” said Brian Richter, president of Sustainable Waters, an organization focused on water scarcity issues. “The result is increasing depletion of rivers, lakes, and aquifers.”

The constraints led Hansen and his wife to explore water-conserving crops. His team planted drought-tolerant, and nutrient-dense White Sonora wheat and mesquite trees.

“We embraced the abundance of heirloom and native crops in the Sonoran Desert,” Hansen said. “We are looking at the land and asking it what we should grow, rather than asking the land to grow what we want.”

Hansen hired farm attendant Juan Carlos Gutierrez and Wang, who shared his vision of healing the land and were knowledgeable about water, soil, and biodiversity. Wang has a bachelor’s degree in chemical engineering and a Ph.D. in agriculture and life sciences. Gutierrez does a bit of everything at the farm, including planting and harvesting, maintaining farm equipment, managing cover crops, rotating animals, and milling wheat and mesquite into flour.

In five years, Oatman Flats Ranch’s regenerative practices saved over a billion gallons of water, doubled the amount of organic matter in the soil, and steadily transformed the once-beleaguered ecosystem, according to its May 2024 Regenerative Impact Report. The water savings are measured by tracking the flow rate of each well on the ranch to calculate the amount of water used per round of irrigation. The acre-feet of water used at Oatman Flats Ranch are then compared to the estimated acre-feet used in conventional wheat production. (One acre-foot is enough water to flood a football field 1 foot deep, or more than 325,000 gallons.)

“When we grow regenerative, we can use 2 or 3 acre-feet of water,” Hansen said. “Alfalfa and cotton will take like 9 or 10 acre-feet.”

To measure soil organic matter, Wang takes samples from the surface of the fields and sends them to the Motzz laboratory in Arizona and the Regen Ag Lab in Nebraska for analysis. Soil organic matter is the key indicator of soil health, influencing nutrient and water availability, biological diversity, and other factors critical in growing healthy crops. In some fields, soil organic matter has grown from 0.8 percent to 2.4 percent, according to the lab results. Yadi said 0.8 percent is about normal for the region, while 2.4 percent is very high, an outlier. “People think it’s impossible,” he said.

Regeneration Rooted in Indigenous Practices

At the Tohono O’odham Indian Reservation, about two hours southeast of Oatman Flats, the San Xavier Co-op Farm uses historic land management practices and grows traditional crops that reflect their respect for the land, plants, animals, elders, and the sacredness of water.

San Xavier Farm Manager Duran Andrews and his team plant cover crops, rotate fields, and collect rainwater. “[Regenerative agriculture] is nothing new to us,” Andrews said. “We have been doing this for decades. Harmony between nature and people has been our approach all the time.” Rotating fields and cultivating multiple mutually beneficial species in the same fields improves water and soil quality and biodiversity in this harsh landscape.

The co-op grows a variety of native crops that were developed in the region and cultivated for centuries or, in some cases, millennia, such as grains and beans, which they sell online. “We irrigate them till they sprout, then cut them off till the monsoon shows up,” Andrews said. “We try to keep crops in that hardy state through all the years and decades they have been here. We try not to get away from how things were done in the past.” They also grow White Sonora wheat, introduced to Arizona by Spanish Jesuit missionaries in the 1600s. “It was a gift from Father Kino that we have taken as our own,” Andrews said. “The [San Xavier] community was one of the first to grow this wheat.”

Following the Mexican-American War in the mid-1800s, the United States claimed parts of modern-day Arizona, New Mexico, California, Nevada, and Utah. The Anglo ranchers who moved into the area dug canals to irrigate agricultural fields, transforming the landscape. An 1852 watercolor by surveyor Jon Russell Bartlett depicts a verdant valley with cottonwoods and mesquite trees lining a flowing Gila River as it passes through Oatman Flats Ranch.

That landscape is unrecognizable today. The lower Gila has gone bone dry after years of upstream diversions, dams, water overuse, and climate change. In 2019, the Gila River earned the title of Most Endangered River by the nonprofit advocacy group American Rivers.

Standing on the sandy Gila riverbed, which divides the north and south farms of Oatman Flats Ranch, Wang pointed to the nearby invasive salt cedars. Healing the land involves rebuilding the water, nutrient, and carbon cycles from the ground up, “at the micro level,” he said. “On the macro level, it’s broken.”

The ranch team has poured resources into rebuilding soil health by planting hedgerows and 30-plus species of cover crops, at a cost of approximately $100,000. The hedgerows, mostly native trees, were planted along the edges of the fields to reduce erosion and provide habitat for beneficial species, including pollinators such as bees and hummingbirds.

The cover crops—millet, chickpeas, sunflowers, sorghum, sudan grass, broadleaves, and native grasses among them—are planted immediately after harvesting wheat, to provide “soil armor,” help conserve water, fix nitrogen in the soil, suppress weeds, attract beneficial insects, and sequester carbon. The once-barren land now supports life for more than 120 species of flora and fauna.

“When you take life away, it just doesn’t come back unless you provide the resources,” said Wang.

The varying heights of the cover crops make multi-storied microclimates, with vapor condensing near the cooler soil surface, creating dew. “I can make dew in the hottest part of July, when the ambient temperature is over 90 degrees by 9 a.m.,” Wang said.

Instead of tilling the cover crops into the fields at the end of their cycle and disturbing soil structure, the team uses a roller-crimper—a ridged cylindrical drum attached to a tractor—to cut stalks and lay the crops down “like a carpet” to protect topsoil, Hansen said. Switching to roller crimping saves money, too, since it costs one-third less than tilling.

The roots remain in the soil, reducing soil erosion and creating an extensive microbial network that cycles nutrients, builds soil organic matter, and increases water infiltration “like a sponge,” Wang said. All of this protects soil from high temperatures, too.

The fields slope ever so gradually to allow irrigation water to move down the rows. In the early years, water would race down the hard-packed dirt, spilling into the Gila drainage. Now, Wang has the opposite problem: When he irrigates, it takes days for water to spread three-quarters down the length of the field. In response, the ranch plans to switch to sprinklers to save water, expand cultivable land, and mimic natural rainfall. The sprinklers are expensive and cost about $1 million, most of that already paid by a water irrigation efficiency grant from the U.S. Department of Agriculture. This move away from flood irrigation is gaining traction in the parched Southwest.

In 2022, Oatman Flats Ranch introduced sheep, natural lawnmowers that prune back cover crops and weeds while fertilizing the soil. They are rotationally grazed from field to field to give plants in each area a chance to recuperate and strengthen their root systems.

Now, six years after regeneration efforts began, 90 animal species have returned to the area around the farm, including mountain lions, owls, and tiny blue dragonflies—”a sign of water,” Wang said—who weave in and out of rows of White Sonora wheat.

Native Crops Adapted for the Arid Southwest

Mesquite trees are superbly adapted desert plants. At the ranch, they’re planted in dense groves near the farmhouse. Their taproots can burrow 200 feet deep, and they can shed their small, waxy leaves—designed to conserve moisture—in extreme drought.

Their green-bean-like pods were a staple food for Indigenous people in this region, rich in fiber, protein, and calcium. When dried and ground into flour, they have a mildly smoky, nutty, molasses-like flavor. Wang’s wife adds the flour to her coffee, making a frothy, slightly sweet, nutrient-packed latte.

White Sonora wheat is a key part of Hansen’s vision for a regenerative grain economy. The wheat is sown in November or December and harvested in late spring or early summer.

Standing in a field of pale golden wheat stalks, Wang threshed the grain from the chaff by rubbing his palms together as if warming his hands on a cold day. The berries resemble tiny deer hooves, with a groove in each golden-colored grain.

“This is as clean as you can get,” Wang said. “No synthetic fertilizer. No chemicals. Drying on the stalk.” The ranch’s cold-stone milling process preserves the grain’s vitamins and minerals, and retains its naturally sweet, mild flavor.

Oatman Flats Ranch sells Regenerative Organic Certified (ROC) products such as stone-milled flour and mesquite flour, as well as bread, pancake, and waffle mixes, under the Oatman Farms brand. The flours and mixes are now used by numerous restaurants, including Arizona Wilderness Brewing Company.

“We are looking to partner with and help sustain farms like Oatman,” said Jonathan Buford, CEO and brewmaster at Arizona Wilderness, which sources sustainable ingredients from more than 50 local producers. “We need to look at a different currency than just capital. We must consider that Earth must profit, too, for the future of our planet.”

Seeding More Regenerative Farms

To better understand how the regenerative movement is evolving, Hansen routinely talks to other farmers, and he’s clear about what must happen for it to really take hold. “It is absolutely true that farmers don’t have the resources to do this on their own,” Hansen said. “Farmers need help from consumers, restaurants, and governments to pull off this regenerative effort. I believe we can make regenerative agriculture viable by explaining the plight of the land and the farmers and nature and boldly proclaiming the solution of regenerative agriculture.”

The transition to a Regenerative Organic Certified (ROC) model can require a large investment, as it has for Hansen. And it takes three to five years to reap the benefits of regenerative practices, according to Elizabeth Whitlow, founder and senior advisor of the Regenerative Organic Alliance (ROA), which oversees the ROC framework and guidelines.

For most farmers, this is not an option. Margins are thin, and financial constraints often inhibit farmers from exploring regenerative practices. “The only option is to do the cheapest thing you can to survive,” Wang said. “[There is] no room to consider what they could do differently.”

The paybacks of regenerative organic farming can be significant, however. They include reduced costs of inputs such as fertilizers, pesticides, and water, as well as increased profits from high-value products. “I do see brands stepping in and up to provide long-term contracts with farmers while they transition into this new, unknown territory,” Whitlow said. “The premiums and long-term stability offered through this kind of contract agreement help the farmers.”

Besides Hansen’s own funds, Oatman Flats Ranch has also been supported by payments from the USDA’s Natural Resources Conservation Service for on-farm conservation programs, such as tree planting and conservation cover. As the Trump administration cuts climate-related programs, Hansen said Oatman Flats would be affected by “the elimination of Arizona statewide programs supporting local food systems.”

Hansen nonetheless believes that in time, a financially viable model for regenerative organic farming is possible, particularly as demand for ROC products grows. A 2022-2023 impact report from the ROA showed that ROC product sales grew 22 percent on average between 2022 and 2023, reaching nearly $40 million. But profitability, he said, will take “quite a while.”

With the growth of regenerative agriculture, Hansen sees the potential to preserve his family’s farm and a way of life he holds dear, especially as the climate changes.

“You’ve seen what the land looks like in five years; imagine it in 10,” Hansen said. “If we can do it here, we can do it anywhere.”

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]]> https://civileats.com/2025/05/12/could-this-arizona-ranch-be-a-model-for-southwest-farmers/feed/ 1 https://civileats.com/2025/04/22/an-ancient-irrigation-system-may-help-farmers-face-climate-change/ Tue, 22 Apr 2025 08:00:13 +0000 https://civileats.com/?p=63608 A version of this article originally appeared in The Deep Dish, our members-only newsletter. Become a member today and get the next issue directly in your inbox. Below, rows of long, narrow fields extended from Culebra Creek toward a man-made channel, the main artery of the valley’s centuries-old “acequia” irrigation system. This was the “People’s Ditch,” a […]

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Below, rows of long, narrow fields extended from Culebra Creek toward a man-made channel, the main artery of the valley’s centuries-old “acequia” irrigation system. This was the “People’s Ditch,” a waterway holding the oldest continuous water right in Colorado. The channel carried water from tributaries of the Rio Grande, high in the Sangre de Cristo mountains, down to the fields below.

There, the flow was diverted into smaller ditches that irrigated fields of alfalfa, cabbage, and potatoes, the water seeping naturally through the earthen walls. In the San Luis Valley as a whole, 130 gravity-flow ditches irrigated 30,000 acres of farmland and 10,000 acres of wetlands.

“This is an incredibly productive, resilient, and sustainable system,” said Peña, founder of The Acequia Institute, a nonprofit that supports environmental and food justice in southern Colorado.

The acequia system was once dismissed by Western water managers. But as a changing climate brings increasing drought and aridification to the Southwest, time-tested solutions like this one could hold the key to mitigating the worst impacts of climate change, especially in rural communities.

“[Water managers] are starting to appreciate us a lot more than they did 20 or 30 years ago when they thought we were backward, primitive, and inefficient,” Peña said.

An Ancient History

The word acequia—from the Arabic word “as-saquiya,” which means “that which carries water”—was used to describe the irrigation ditches that evolved in the Middle East and were introduced to the Iberian Peninsula during the Islamic Golden Age. In New Mexico, these systems were often put in place even before a church was built.

Acequias operate under the principle of “shared scarcity,” rooted in Islamic law, whereby every living thing has a right to water, and to deny them water is a mortal sin. Water is thus treated as a communal resource to be shared, rather than divvied up and contested.

“They all share something in common, which is community governance,” Peña said. “It’s a water democracy.”

An acequia is both a physical canal system and a political structure, which includes an elected mayordomo, or ditch boss, along with commissioners who govern management and operations. Acequias are self-sufficient and collectively owned by members, each with water rights to the ditch and an equal vote regardless of property size.

The Spanish built acequias throughout the Southwest, but most in Arizona and California were abandoned or replaced by modern irrigation systems. In Texas, a few remain, including the San Antonio Mission Acequias.

“Our ancestors and predecessors created a cultural landscape and spread a broad ribbon of life that is an extension of the river,” said Paula Garcia, executive director of the grassroots New Mexico Acequia Association. “They have literally shaped the landscape.”

Acequias are central to the system’s resilience and adaptability, New Mexico State University hydrologist Sam Fernald said. “By having people on the ground, connected to every drop, they are able to adapt,” he said. “They have been adapting to changes in water and land for 400 years.”

Unlike conventional irrigation systems, the physical design of the acequias mimics natural hydrological and ecological functions, slowly distributing water throughout the landscape through unlined ditches that allow seepage. This “keeps surface and groundwater connected,” Fernald said, recharging the aquifer, reducing evaporation and aridification, enhancing biodiversity, and returning flows to the river.

A Model for Modern Times

But the modern system is under stress, as a changing climate reduces mountain snowpack, the main source of Western water. Snowpack acts as a water bank that holds frozen water in the mountains into the spring and releases it throughout the summer. Changing climate patterns also mean shifts in melt patterns, and all of this makes managing water flows through dams a challenge.

Adding to the uncertainty, the Trump administration is making cuts to the Interior Department’s Bureau of Reclamation, which manages dams, and President Donald Trump has shown a willingness to demand water releases himself, as he did recently with two dams in California, to the consternation of farmers and water managers.

“The acequias and Rio Grande have given life, food, and shelter to people and wildlife, but they’re at risk if we don’t value and better adapt these systems and ecosystems for future conditions,” said Yasmeen Najmi, a planner for Middle Rio Grande Conservancy District, which helps manage irrigation in the valley, including the acequias.

Industrial agriculture exacerbates climate change through its use of synthetic fertilizers, whose production generates significant fossil-fuel emissions, and soil tillage, which disrupts soil’s ability to capture carbon. According to José Maria Martín Civantos, an expert in landscape archaeology at the University of Granada, in Spain, this kind of agriculture is “literally building the desert.”

By contrast, traditional irrigation systems like acequias enhance water quality, expand wildlife habitat, increase soil fertility, and—crucially—support highly productive food systems.

After New Mexico was ceded to the U.S. in 1848, Americans quickly recognized the productivity of acequia agriculture, said Sylvia Rodriguez, an anthropologist and author who grew up in an acequia community in Taos, New Mexico. “American takeover incorporated the acequia system into the state statutes because it was so efficient. Local management is hard to improve on,” she said.

Acequia Soil and Community

In an acequia community, land-based ecological knowledge is passed down through generations along with time-tested practices such as companion cropping, crop rotation, seed-saving, fire ecology, and agroforestry. “Literally all the tenets of regenerative agriculture that were here well before anyone was talking about it,” Peña said. Many of these practices originated with Indigenous farmers.

Sustainable acequia irrigation regenerates the soil horizon, bringing mineral and sediment-rich water from the mountains to the fields. While acequias remain the primary irrigator in northern and central New Mexico, small-scale farming has declined in the region through massive economic restructuring, depopulation of rural areas, and the move from diversified crops to monocultures.

Today, few farmers grow food in the region. “We’ve become an alfalfa monoculture and beef export colony,” said Peña. “We need to transform farming back to polyculture.”

For Peña, local water management improves soil and crops. But it also means self-determination when it comes to healthy food. On the Acequia Institute’s 181-acre farm, Peña and others are reviving traditional farming practices and crops such as heirloom corn, beans, and squash.

The institute also provides no-interest loans to acequia farmers who are paid by the acre instead of by yield. Farmers have access to youth interns through the Move Mountains Project, aimed at creating “the next generation of farmers,” Peña said.

In 2022, the Acequia Institute purchased R&R Market, the oldest grocery store in Colorado, which was going to close. The institute is converting the space into a worker-led community co-op, a place to distribute the bounty of the acequia system.

The market, now renamed The San Luis Peoples Market, will reopen in late April and include a grocer, deli, commercial kitchen, community center, and market featuring produce from acequia farmers in the valley. In the years to come, Peña plans to open a second commercial kitchen, a USDA-certified slaughterhouse, and a solar-powered greenhouse.

“I know we’re going to bring healthy food and nutrition to the community,” Peña said, as the storm clouds above Culebra Peak cleared. “The model is, we don’t want to go outside the valley.”

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]]> https://civileats.com/2024/04/22/seeds-from-wild-crop-relatives-could-help-agriculture-weather-climate-change/ Mon, 22 Apr 2024 09:00:22 +0000 https://civileats.com/?p=55991 The isolation of this ecologically rich archipelago of peaks, located in a “sea” of desert that stretches from northern Mexico into southern Arizona, means that plants grow here that don’t grow anywhere else. Its 2,800 acres—the first protected habitat for the wild relatives of crops in the United States—now shelter not just a single pepper but […]

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In the rugged Tumacácori mountain region 45 minutes south of Tucson, the Wild Chile Botanical Area (WCBA) was established in 1999 to protect and study the chiltepin pepper—the single wild relative of hundreds of sweet and hot varieties including jalapeño, cayenne, and bell peppers, found on dinner plates worldwide.

The isolation of this ecologically rich archipelago of peaks, located in a “sea” of desert that stretches from northern Mexico into southern Arizona, means that plants grow here that don’t grow anywhere else. Its 2,800 acres—the first protected habitat for the wild relatives of crops in the United States—now shelter not just a single pepper but at least 45 different species.

Between 2021 and 2022, the Borderlands Restoration Network (BRN), an Arizona-based conservation non-profit, worked with the U.S. Forest Service to identify and collect other wild relatives of crops in this area. The idea behind the project was to build food security in a world where all climate models are pointing to hotter and dryer extreme conditions.

“You have this dramatic topography that provides all these different ecological niches for different things to grow,” said Perin McNelis, 36, native plant program director at the BRN. “Where better to start than an area that is already hot and dry, with all these wild relatives that are really adapted to conditions that will be more widespread in the future.”

Crop wild relatives, or CWRs for short, are the hardy wild cousins of domesticated crops. In the U.S. alone, thousands of crop wild relatives exist in their natural habitats, often thriving in harsh conditions. In Arizona this includes wild species of onion, wheat, squash, strawberry, grape and many other important crops.  Increasingly, farmers and scientists are looking at them as reservoirs of genetic diversity with traits that can be bred into domesticated crops to improve drought, heat, and disease resistance—and perhaps serve as the key to the future of farming.

“What makes them important is they have traits that can help crops be more adapted and resilient to climate change,” said Stephanie Greene, a retired plant geneticist for the U.S. Department of Agriculture’s (USDA) Agricultural Research Service.

Erin Riordan, a conservation research scientist at the Arizona-Sonora Desert Museum outside Tucson, works to expand the regional food system to include dryland-adapted plants such as agave, mesquite, prickly pear, and tepary beans with low-water use agricultural practices. For instance, tepary beans—a tiny brown bean with a sweet chestnut flavor—require about 1/5 the water of pinto beans.

Arizona is the third driest state in the U.S. It also has the highest diversity of crop wild relatives due to the state’s wide-ranging topography and habitats, “from low deserts to high elevation alpine, to everything in between,” said Riordan. One thousand of the estimated 4,500 CWRs in the U.S. are found in the state, including desert-adapted relatives of critical domesticated foods—not just peppers, but also tomatoes, squash, amaranth, beans, corn, and wheat.

An Arizona Walnut tree. (Photo CC-licensed by Whitney Cranshaw, Colorado State University.)

Wild cotton grows in the parched grasslands of the Sonoran Desert, surviving without irrigation, pesticides, or other human inputs that domesticated cotton depends on. The wild Arizona walnut, found in desert riparian areas,  has been used as a rootstalk for domesticated walnut trees to increase their tolerance to drought and diseases.

Currently, 44 percent of the world’s food is produced in arid and semi-arid lands. According to a 2017 report from the Food and Agricultural Organization of the United Nations, “80 percent of global cropland and 60 percent of global food output could be markedly affected by climate change, particularly in arid and semi-arid areas.” Riordan said protecting desert-adapted CWRs will be particularly important in a changing climate.

One issue complicating the use of wild relatives as a solution, however, is that these banks of genetic resilience are under threat through habitat destruction and global biodiversity loss caused by development and climate change. A 2020 paper in the National Academy of Sciences’ journal found that over half of the 600 CWRs identified in the study were either endangered or threatened. When a wild species goes extinct, so do the evolutionary traits that have allowed it to survive environmental extremes.

While the momentum for studying and conserving crop wild relatives has grown in recent years, few CWR species are protected at either a state or federal level. Arizona has been at the forefront of conservation efforts, protecting CWRs on public lands like the WCBA, at botanical gardens like at the Desert Museum, and at seed banks.

Heat Stress, Water Scarcity, and the Need to Adapt

Last year was the world’s hottest summer on record; in Arizona, temperatures routinely exceeded 110 degrees. Across the state, crops withered in the punishing dry heat, and farmers left land fallow amid statewide water cutbacks driven by a historic megadrought.

“These last few years are indicative of the sorts of extreme conditions that are increasingly becoming the new norm,” Riordan said. “Arizona farmers have always experienced periodic drought and bouts of heat, but these events are happening with greater frequency, becoming more severe, and lasting longer.”

At the same time, other sources of water are becoming increasingly scarce in the west, putting stress on farmers and making some crops untenable. Last year, Arizona’s allotment from the Colorado River was cut by 21 percent.

“These last few years are indicative of the sorts of extreme conditions that are increasingly becoming the new norm.”

Benjamin Ruddell, director of the National Water-Economy Project, said that Colorado River water shortages left large areas of farmland in Arizona unsowed, a bellwether of things to come. “Up to 40 percent of farmland has been fallowed in some parts of Arizona,” he wrote in an email. Additionally, in some parts of the Southwest, states are paying farmers to fallow their fields to save water.

According to the Arizona Department of Water Resources, three quarters of Arizona’s total water supply is used for agriculture. “It’s going to be increasingly less feasible to irrigate things,” said Riordan. “If you’re not relying on surface flows, you’re relying on fossil water [groundwater], and we don’t have enough rain to be recharging.”

Dr. Michael Kotutwa Johnson, a Hopi dryland farmer and academic, pointed out that for millennia, Hopi farmers have successfully farmed, without irrigation, on ancestral lands that receive an average of 10 inches of rain or less per year. Farmers plant seeds deep in the soil, use passive rainwater harvesting, and rely on hardy desert-adapted seeds. “Our seeds are very resilient,” said Johnson. “They are just amazing in the way they can survive heat and lack of irrigation.”

Johnson said that unlike conventional farming, every aspect of Hopi farming has been refined to retain soil moisture with agricultural practices and crops that fit the environment, not the other way around.

Counter to this approach, many crops grown in Arizona require vast amounts of water and are maladapted to the environment, Johnson said. “As the temperature increases in Arizona, more water will be needed for commodity crops like cotton and alfalfa,” he said. “Those two crops are not place-based and will require even more water in the future.”

For Johnson, statewide water scarcity will require a move away from these water-thirsty crops towards desert-adapted varieties. “We need crops that use less water,” he said.

“Our seeds are very resilient. They are just amazing in the way they can survive heat and lack of irrigation.”

Author and ethnobotanist Gary Nabhan has been studying crop wild relatives for over 50 years. According to Nabhan, plant breeders and agronomists have been slow to accept the fact that we need desert-adapted crops, even as all signs point to a hotter, dryer future. “For nearly a century, crop wild relatives were neglected because plant breeders did not need drought and heat tolerance as long as they had plenty of irrigation water,” said Nabhan.

As a university student in the late ‘70s, Nabhan recalls a professor explaining why desert-adapted crops were unnecessary. “‘The more water you put on a crop, the more yield you get. We have the water, so why would you want to go back?’” said Nabhan of the conversation. “I mean, it’s just amazing in retrospect that he said that to me in 1976. [They saw] water as unlimited.”

With growing heat stress and water scarcity, breeders will increasingly need the genetics from their desert-adapted cousins to survive. “Wild crop relatives will be the only alternative to deal with climatic changes on two fifths to one half of the continental U.S.,” said Nabhan about the impact of global warming on our semi-arid and arid lands.

Nationally, the Botanic Garden Conservation International (BGCI) and the U.S. Botanic Garden (USBG) are working to increase the number of crop wild relatives at botanical gardens to fill gaps in gene bank collection and maintain samples from wild populations.

But while some are working to identify and protect CWRs, Nabhan believes much more needs to be done. “Federal agencies have hardly ever invested time or funds in their protection or management,” he said.

Protecting and Breeding CRWs

Access to the critical traits crop wild relatives possess requires protection both in the wild and in the lab, said Riordan and the BRN’s McNelis.

Both are proponents of a “trans-situ” approach to CWR conservation, or the combination of in-situ (on-site) protection of plants in their native habitats and ex-situ (off-site) conservation at seedbanks, gene banks, and gardens. “We have these important efforts to conserve them, both through protecting their wild habitats and through these backup collections,” said Riordan.

Once researchers identify a desirable trait, breeders can cross pollinate the CWR with a domesticated crop. “The more genetically related the CWR and crop, the easier this is to do,” said the USDA’s Greene.

Examples of wild and domesticated forms of crops. The first image of each row is the wild relative. a) teosinte and maize (Zea mays); b) chilli pepper (Capsicum annuum); c) common bean (Phaseolus vulgaris); d) cotton (Gossypium hirsutum). (Images CC-licensed, from Botanical Sciences 95(3):345).

Past examples include breeding wild wheat with domesticated varieties to boost disease resistance. Wild relatives of potatoes have been used to increase frost resistance and blight—the cause of the devastating Irish potato famine in the mid-19th century. Sunflower wild relatives “have contributed genes for disease resistance, salt tolerance, and resistance to herbicides,” said Greene.  Another notable success story was the introduction of hardy American grape rootstalks to help counter Phylloxera, an aphid-like insect that nearly wiped out European Vitis vinifera.

Nabhan said root stalks from crop wild relatives, such as grapes, hold vast potential as well. “Using hardy wild root stalks on grapes, apples, raspberries, blackberries is really viable,” he said. This is already being done on a commercial level. . . . It’s not pie in the sky.”

Increasingly scientists are using molecular techniques to bring adaptive traits from CWRs into domesticated species through precise genome editing. Using CRISPR, researchers have modified genes from wild tomato relatives to increase fruit size and nutrition in an engineered tomato crop.

A Botanical Area and a Desert Museum

In Arizona’s Wild Chili Botanical Area, unique regulations help protect the CWRs, including an exclusion on cattle, limits on extractive industries such as mining, and the banning of road construction.

To identify CWRs in the area during the recent survey, McNelis explored a remote portion of the Coronado National Forest, helping identify high-priority species such as canyon grapes, desert cotton, black walnut trees, tepary beans, and wild relatives of corn and wheat. She found many species surviving in nutrient-poor soils, growing on rock faces, or in overgrazed and disturbed environments.

“It really does speak to what persists in this landscape,” said McNelis. Her experience reinforced the importance of preserving CWR in what she described as an era of mass extinction. “The genetic material holds so much potential for creating more resilient crops in a world where extreme climate events are likely to occur.”

Meanwhile, at the Arizona-Sonora Desert Museum, Riordan is heading up a first-of-its-kind research program to conserve arid-adapted crop wild relatives. The 98-acre complex is a combination of zoo, aquarium, natural history museum, and botanical garden that includes one the largest living collections of crop wild relatives in the United States.

“The Desert Museum is leading an effort to better understand and conserve the CWRs of the Sonoran Desert region by documenting important species, developing conservation priorities, and building partnerships,” including a collaboration with the Desert Museum in Phoenix and the Chicago Botanical Garden, said Riordan of the project.

“Botanical gardens like this one play a key role in conservation,” said Riordan, as we walk past a mountain lion in the mountain woodland exhibit. Organized into various biomes of the Sonoran Desert, the museum has over 200 CWRs in its live plant and seed bank collections. One-hundred-thirty crop wild relatives are grown outdoors in the climate of southern Arizona, where desert adaptions can be maintained.

“We need to keep that selective pressure of the heat and the drought on the plants,” said Riordan, pausing at a  grapevine covering a section of rock wall. This crop wild relative, Vitis arizonica, grows in the canyons of Arizona and is being studied for its potential to improve disease resistance in wine grapes.

Other important CWRs at the museum include relatives of domesticated beans, sunflowers, and peppers–including the chiltepin, which also thrives in the mountains and canyons of northern Mexico. “I picked them from the side of the road in Sonora,” she said, opening a plastic container with a few dozen sun-dried samples. The fiery peppers have a fruity vegetable aroma and a smoky sweet heat that builds and lingers.

Later, we pass a wild tepary bean plant, the ancestor of the legume domesticated by Indigenous Sonorans many centuries ago.

From her satchel, she takes out a container of the small speckled wild beans, along with another bag holding a dozen or so brown domesticated versions. These cultivated teparies are nutrient and protein dense and far more climate resilient than the much more common pinto bean.

“[This is] a result of thousands of years of native desert peoples domesticating a wild plant into an incredibly heat-hardy and drought tolerant crop,” said Riordan.

Further along the path is a desert cotton plant—long utilized by indigenous Sonorans. A ProPublica investigation found that conventional cotton grown in Arizona requires six times more water than lettuce and 60 percent more than wheat. Its existence is made possible by massive federal subsidies and billions of gallons of water imported into Arizona to grow cotton as well as water-thirsty crops such as alfalfa, corn, and pecans.

Though it bears a close physical resemblance to domesticated cotton, the drought-tolerant shrub growing in the botanical garden requires a fraction of the water. This species, she explained, has been researched for “drought resistance, salt tolerance, pest resistance, and crop quality.” It is also critically endangered.

“It’s thousands of years of adaptation,” said Riordan. “When it’s gone, it’s gone.”

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