BAO LOC, Vietnam — For decades, the world of coffee has had one star: the arabica bean. It is “complex” and “deliciously refined,” according to companies such as Starbucks that have refused to use any other bean. It has engendered obsession among java aficionados.

But climate change, as it tends to do, is shifting fortunes.

The sophisticated arabica is hypersensitive to fluctuations in temperatures and faces dim prospects in a warming world. Once spurned as its “ugly stepsister,” the bulkier robusta plant — so named because it grows robustly in tough conditions — is mounting its revenge.

Vietnam is responsible for more than half of the global robusta supply, government data shows, and it plays an increasingly vital role in efforts to rescue coffee from the effects of climate change. The robusta farmed here, on the rolling hills of Vietnam’s central highlands, is more resilient and has higher yields than virtually anywhere else, scientists say, with some varieties producing two or three times more beans than varieties in other parts of the world.

Vietnam's central highlands, home of the robusta 

Researchers are trying to produce a climate-resistant "super-coffee" in Bao Loc. 

“Arabica is no longer enough to satisfy appetites,” Nguyen Nam Hai, chair of Vietnam’s Coffee and Cocoa Association, said one recent afternoon in a Ho Chi Minh City neighborhood crowded with trendy coffee shops. “And Vietnamese robusta, everyone knows, is number one in the world.”

Much of the pivot to robusta is by necessity. In 2021, a severe frost in Brazil damaged up to 200,000 hectares (494,000 acres) of predominantly arabica coffee crops, leaving behind scars that may take years to heal. Back-to-back hurricanes have battered arabica coffee fields in Honduras, while unpredictable changes in rainfall have devastated coffee farmers in Colombia.

“Climate change has made many issues, mostly for the arabica-producing countries,” said Vanúsia Nogueira, executive director of the International Coffee Organization, a London-based intergovernmental association of coffee-producing countries.

Last year, low output from Brazil, the world’s biggest producer, helped to drive Vietnamese coffee exports to a record $4 billion, more than 30 percent higher than the year before, according to Vietnamese officials. More than 93 percent of the coffee Vietnam produces is robusta.

The robusta plant isn’t insulated from the effects of climate change — it’s sensitive to drought, for example — but agronomists generally agree that it has evolved to be more tolerant of temperature fluctuations than arabica. Significant research is being poured into robusta, widely understudied until recently.

In Bao Loc, a quiet agricultural town two hours from the tourist city of Dalat, Vietnamese and European researchers are experimenting with ways to replicate the phenotype of native robusta varieties that have proved exceptionally resilient to pests and heat.

Communities are “preparing,” said Toi Nguyen, a local farmer. “Because the future of coffee,” he added, “is here.”

Using new farming and processing techniques, Nguyen, 48, has produced some of the first robusta coffee accepted by international judges as high-quality. His beans, which he sells for three times the market price of regular robusta, deliver brews with a clean taste and none of the bitter, rubbery flavor that have typically relegated robusta to instant coffee, he said. He’s found fans in Vietnam, France and Japan, and is part of a small but buzzy movement to remake the reputation of robusta.

“Vietnam will play a significant role not only in producing robusta but in educating the rest of the world on how to do it,” said Sahra Nguyen, the Vietnamese American founder of Nguyen Coffee Supply, which has pushed retailers such as Whole Foods and Blue Bottle Coffee to begin embracing the bean. Farmers and roasters in Vietnam are “the most educated and the most innovative” when it comes to robusta, Nguyen said by phone from Brooklyn. They’ve refined methods of processing it with natural substances and pioneered ways of fermenting it in oxygen-free conditions to release new flavors.

Producers elsewhere are increasingly interested in learning these techniques, including in Latin America, where countries that have long focused on arabica are beginning to test their ability to grow robusta, said Nogueira of the International Coffee Organization.

Arabica still has its faithful fans — even in Vietnam, specialty coffee shops largely serve it, and many are proud to say they serve only arabica — but “more now, what people are realizing is they will need another option, in addition to the arabica, for the future,” said Nogueira, who is Brazilian.

In Bao Loc, this effort has arrived at the stumpy feet of a native variety of robusta that locals call the “green dwarf.”

Its technical name is “Truong Son 5” after the farmer who first debuted it at a local pageant for coffee trees. Thick and stocky, it earned its nickname, locals said, because of its stubborn resistance to environmental threats, from parasites to coffee leaf rust, a fungus that has devastated farms in Central America.

The Vietnamese government recently approved TS5 as a specialized variety, worthy of being studied and replicated. And last year, the European Union greenlighted a project with the commodities trader ECOM Agroindustrial to examine how to graft rootstock from TS5 and other hardy varieties onto weaker robusta plants and, potentially, onto other coffee species.

The goal, said lead researcher Thuan Sarzynski, is to create a kind of “super coffee” that withstands all manner of climate threats. Apart from robusta, the project is experimenting with other species of coffee, including liberica, which has deep roots that make it hardy against drought. Liberica accounts for less than 2 percent of global production but has long been grown in small quantities in this part of Vietnam. Many local farmers have tried on their own to graft robusta onto liberica, and one of the project’s aims, Sarzynski said, is to study that process to see if it can produce a drought-resistant, high-yield coffee of the future.

One afternoon under the blazing sun, Nguyen Trung Than bent over a row of TS5 trees, nearly all of a consistent height and size. “Look,” said Than, the plants’ caretaker, as he held up a dense cluster of coffee cherries just beginning to bud. Come harvesting season, he explained, they would each produce as much as 30 kilograms (66 pounds) of coffee cherries, or about twice as much as some other varieties.

Vietnam’s central highlands are cooler than the rest of the country, but the start of the summer meant that temperatures were still climbing past 85 degrees. Than wiped his brow.

How did the green dwarves fare under the heat?

“Well,” he said, smiling proudly, “they’re not scared.”

Researchers are confident there are other varieties of robusta in Vietnam with qualities worth studying. But to protect them, experts say, farmers need to stop overtaxing their land in pursuit of more production, a difficult thing to ask in a part of the country that has traditionally lagged in development and poverty reduction.

Decades of intense fertilizer use and monoculture — the cultivation of a single crop to maximize its production — have degraded growing conditions in the central highlands, said Bui Dac Hao, a Vietnamese program manager for IDH, a nonprofit focused on sustainable trade. Coffee distributors are pushing smallholder farmers to cut back on their use of fertilizer and grow other plants — a method called intercropping — to avoid exhausting their land.

In 2018, IDH launched a pilot program in Di Linh, a district bordering Bao Loc, that gave farmers incentives to plant avocado, durian and other fruit trees on their plantations. “It took us a long time to convince them,” Hao said, but by last year, the percentage of farmers engaging in intercropping had jumped from 7 to 62 percent.

Organic farming isn’t just good for the land; it’s good for the bean, said Toi Nguyen, the Bao Loc farmer. For the past five years, Nguyen has been restoring an old, exhausted coffee farm to a more natural state, introducing native trees and letting weeds and vines of black pepper crowd over the trunks of the coffee plants. Farming this way makes stronger robusta and eventually, Nguyen said, tastier coffee.

At his warehouse, he opened a sack of the past season’s cherries, colored dark red because, unlike most robusta farmers, he only picks ripened cherries. He scooped a handful to his nose.

“Smells like candy,” he said, his eyes crinkling.

The youngest child of rice farmers, Nguyen grew up in poverty and, not too long ago, made his living selling corn by the roadside, he recalled. His entrance into specialty coffee has been unexpected even to him. But he’s just getting started, he said.

“I want to go deeper, higher into quality,” Nguyen said, “I want to find the limit.”

In a few days, he was set to travel to Portland, Ore., where he would show off his beans at the largest coffee event in North America. He was nervous about the long flight and about talking to people because he spoke almost no English. But he wasn’t nervous at all, he said, about the coffee.

He tapped on his cup, swirling with the final dregs of a fresh brew. It spoke for itself, he said.