A blanket of bright green alfalfa spreads across western Arizona's McMullen Valley, ringed by rolling mountains and warmed by the hot desert sun.

Matthew Hancock's family has used groundwater to grow forage crops here for more than six decades. They're long accustomed to caprices of Mother Nature that can spoil an entire alfalfa cutting with a downpour or generate an especially big yield with a string of blistering days.

But concerns about future water supplies from the valley's ancient aquifers, which hold groundwater supplies, are bubbling up in Wenden, a town of around 700 people where the Hancock family farms.

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Some neighbors complain their backyard wells have dried up since the Emirati agribusiness Al Dahra began farming alfalfa here on about 3,000 acres several years ago.

It is unknown how much water the Al Dahra operation uses, but Hancock estimates it needs 15,000 to 16,000 acre feet a year based on what his own alfalfa farm needs. He says he gets all the water he needs by drilling down hundreds of feet. An acre-foot of water is roughly enough to serve two to three U.S. households annually.

Hancock said he and neighbors with larger farms worry more that in the future state officials could take control of the groundwater they now use for agriculture and transfer it to Phoenix and other urban areas amid the worst Western drought in centuries.

"I worry about the local community farming in Arizona," Hancock said, standing outside an open-sided barn stacked with hay bales.

Concerns about the Earth’s groundwater supplies are front of mind in the lead-up to COP28, the annual United Nations climate summit opening this week in the Emirati city of Dubai. Gulf countries like the UAE are especially vulnerable to global warming, with high temperatures, arid climates, water scarcity and rising sea levels.

"Water shortages have driven companies to go where the water is," said Robert Glennon, a water policy and law expert and professor emeritus at the University of Arizona.

Experts say tensions are inevitable as companies in climate-challenged countries like the United Arab Emirates increasingly look to faraway places like Arizona for the water and land to grow forage for livestock and commodities such as wheat for domestic use and export.

"As the impacts of climate change increase, we expect to see more droughts," said Karim Elgendy, a climate change and sustainability specialist at Chatham House think tank in London. "This means more countries would look for alternative locations for food production."

Without groundwater pumping regulations, rural Arizona is especially attractive, said Elgendy, who focuses on the Middle East and North Africa. International corporations have also turned to Ethiopia and other parts of Africa to develop enormous farming operations criticized as "land grabbing."

La Paz County Supervisor Holly Irwin welcomes a recent crackdown by Arizona officials on unfettered groundwater pumping long allowed in rural areas, noting local concerns about dried up wells and subsidence that's created ground fissures and flooding during heavy rains.

"You’re starting to see the effects of lack of regulation," she said. "Number one, we don’t know how much water we have in these aquifers, and we don’t know how much is being pumped out."

Irwin laments that foreign firms are "mining our natural resource to grow crops such as alfalfa ... and they’re shipping it overseas back to their country where they’ve depleted their water source."

Gary Saiter, board chairman and general manager of the Wenden Domestic Water Improvement District, said utility records showed the surface-to-water depth at its headquarters was a little over 100 feet in the 1950s, but it's now now about 540 feet.

Saiter said that over those years, food crops like cantaloupe have been replaced with forage like alfalfa, which is water intensive.

"I believe that the legislature in the state needs to step up and actually put some control, start measuring the water that the farms use," Saiter said.

Gov. Katie Hobbs in October yanked the state’s land lease on another La Paz County alfalfa farm, one operated by Fondomonte Arizona, a subsidiary of Saudi dairy giant Almarai Co. The Democrat said the state would not renew three other Fondomonte leases next year, saying the company violated some lease terms.

Fondomonte denied that, and said it will appeal the decision to terminate its 640-acre (259-hectare) lease in Butler Valley. Arizona has less control over Al Dahra, which farms on land leased from a private North Carolina-based corporation.

Glennon, the Arizona water policy expert, said he worked with a consulting group that advised Saudi Arabia more than a decade ago to import hay and other crops rather than drain its aquifers. He said Arizona also must protect its groundwater.

"I do think we need sensible regulation," said Glennon. "I don’t want farms to go out of business, but I don’t want them to drain the aquifers, either."

Seeking crops for domestic use and export, Al Dahra farms wheat and barley in Romania, operates a flour mill in Bulgaria, and owns milking cows in Serbia. It runs a rice mill in Pakistan and grows grapes in Namibia and citrus in Egypt. It serves markets worldwide.

The company is controlled by the state-owned firm ADQ, an Abu Dhabi-based investment and holding company. Its chairman is the country’s powerful, behind-the-scenes national security adviser Sheikh Tahnoon bin Zayed Al Nahyan, a brother of ruler Sheikh Mohammed bin Zayed Al Nahyan.

The company did not respond to numerous emails and voicemails sent to its UAE offices and its subsidiary Al Dahra ACX in the U.S. seeking comment about its Arizona operation.

But on its website, Al Dahra acknowledges the challenges of climate change, noting "the continuing decrease in cultivable land and diminishing water resources available for farming." The firm says it considers water and food security at "the core of its strategy" and uses drip irrigation to optimize water use.

Foreign and out-of-state U.S. farms are not banned from farming in Arizona, nor from selling their goods worldwide. U.S. farmers commonly export hay and other forage crops to countries including Saudi Arabia and China.

In Arizona’s Cochise County that relies on groundwater, residents worry that the mega-dairy operated there by Riverview LLP of Minnesota could deplete their water supplies. The company did not respond to a request for comment about its water use.

"The problem is not who is doing it, but that we are allowing it to be done," said Kathleen Ferris, a senior research fellow at the Kyl Center for Water Policy at Arizona State University. "We need to pass laws giving more control over groundwater uses in these unregulated areas."

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A former director of the Arizona Department of Water Resources, Ferris helped draw up the state’s 1980 Groundwater Management Act that protects aquifers in urban areas like Phoenix but not in rural agricultural areas.

Many people mistakenly believe groundwater is a personal property right, Ferris said, noting that the Arizona Supreme Court has ruled there's only a property right to water once it has been pumped.

In Arizona, rural resistance to limits on pumping remains strong and efforts to create rules have gone nowhere in the Legislature. The Arizona Farm Bureau has pushed back at narratives that portray foreign agribusiness firms like Al Dahra as groundwater pirates.

The state is "the wild West" when it comes to groundwater, said Kathryn Sorensen, research director at the Kyl Center. "Whoever has the biggest well and pumps the most groundwater wins."

"Arizona is blessed to have a very large and productive groundwater," she added. "But just like an oil field, if you pump it out at a significant rate, then you deplete the water and it’s gone."