The research team’s task was as lofty as the mountains they scaled in December 2018. Their mission? To find a coffee species not seen for nearly 70 years in Sierra Leone.
Until the expedition in 2018, when researchers found one plant of Coffea stenophylla in the largely deforested Kasewe Hills.
The moment was bittersweet. To regrow the elusive species, they needed to cross this plant with another — but a second stenophylla plant was not in sight. A few days later, they ventured to Kambui Hills. After just an hour of hiking — a drop in the bucket compared with Sarmu’s four-year search — they uncovered 20 plants. At all life stages, stenophylla was flourishing: seedlings, saplings and trees.
“Then, we knew we had something to build upon in terms of rescuing the species,” recalls Jeremy Haggar, a researcher on the team and a professor of agroecology at the University of Greenwich.
One hundred twenty-four coffee species exist, but most coffee drinkers are only familiar with two: arabica and robusta. Arabica accounts for 60 percent of traded coffee annually, while robusta trails at 40 percent. According to the U.S. Department of Agriculture, nearly 165 million bags of coffee are produced worldwide each year. But for the coffee industry to adjust to a warming climate, farmers will need to grow multiple coffee species in addition to those commonly enjoyed today. Species with climate resilience, remarkable flavor and scalability — such as stenophylla — are prime candidates.
Climate change has already caused ripples in the coffee industry. Brazil, the supplier of a third of the world’s coffee, recently experienced its worst frost in at least 40 years, driving prices higher. By 2050, coffee demand is forecast to triple — but the way coffee has been produced up to this point cannot be scaled to rise to that challenge.
“Even though you’ve got these two species which cover a range of climatic conditions, it’s really not going to be enough in terms of adapting to climate change,” explained Aaron Davis, the lead researcher on the study and a senior research leader at the Royal Botanic Gardens, Kew.
Upping coffee production is like building upon a feeble house of cards — arabica-growing hot spots will become too warm for the crop in the decades to come, shrinking yields of the foundational species we rely upon today. As temperatures rise, arabica may also lose its quality of taste historically lauded by specialty coffee circles.
“If we were talking about this 10 years ago, they would say, ‘We’ll find a more climate-resilient arabica,’ ” Davis said. Yet, developing a climate-resilient arabica calls for drastic measures such as breeding or genome editing. “We’ve done a lot of work in Ethiopia — we’ve surveyed a lot of wild populations, a lot of cultivated plants — and arabica is really fixed to its niche. It doesn’t have the required variation in its climatic plasticity to really deal with climate change.”
Stenophylla, the recently rediscovered species in Sierra Leone, can withstand heat that arabica cannot, growing at temperatures up to 11 degrees Fahrenheit higher. Since its rediscovery, scientists are investigating how to expedite its growth and augment its yield. Though stenophylla is far from being ready to export, progress is steady.
Stenophylla’s potential has excited Sierra Leone residents, including 28-year-old, self-taught coffee roaster Hannah Tarawally. Coffee production slowed in the wake of her country’s civil war, which ended in 2002. Determined to reconnect farmers to coffee markets, Tarawally founded the Freetown-based roaster Coffee Couriers, one of Sierra Leone’s first dedicated coffee shops.
Tarawally roasts a blend of robusta and arabica every two weeks. Stenophylla is not available to local roasters yet, but once it is, it will transform Tarawally’s line of work. Following the struggle to revitalize local coffee production in the war’s aftermath, Tarawally deemed stenophylla as a “savior” to her community.
“It’s going to grow the economy of our country, so we are very excited,” Tarawally shared.
But climate-resilient coffee only becomes a scalable solution if its taste is so exceptional it catapults demand. And when it does, it creates opportunities on the ground where the coffee is roasted. Tarawally expects demand for the new bean to soar given its unique taste.
Stenophylla balances fruity and floral flavors with notes of peach, blackcurrant, elderflower syrup and jasmine. The Specialty Coffee Association rates coffees on a 100-point scale; those that rise above 80 points are among specialty coffee’s highest ranks. Stenophylla scored 80.25 points, alluding to its prospect of being embraced by global markets. And if it is, Tarawally hopes to “create more employment for our youths, especially females” to match rising demand.
Another bean key to coffee’s climate adaptation is one that is in rotation now but has been historically underestimated: robusta.
In the past, robusta’s heavy flavors of oak and tobacco have excluded the bean from specialty coffee spaces, but its climate potential is creating opportunities to upend this deep-rooted perception.
Despite sensitivity to drought, robusta can tolerate higher temperatures than arabica. And unlike arabica, robusta is resistant to coffee leaf rust, a fungus-induced disease that has caused coffee yields to plummet globally for 150 years. The fungus’s spores, brown just like rust, blanket the tops of coffee leaves, blocking sunlight vital to its growth.
Robusta’s potential has captured the attention of 35-year-old entrepreneur Sahra Nguyen, who sells single-origin robusta via Nguyen Coffee Supply, the company she founded in 2018.
“When I was starting out, I really felt like I was going up against the entire industry because the entire industry was very, very explicit and open about upholding this narrative of ‘arabica is superior, robusta is inferior,’ ” Nguyen said.
Robusta is the tried and true bean of Vietnam, which produces about 20 percent of the world’s coffee supply, amounting to 30 million bags. All but a mere 3 million of these bags are robusta.
Nguyen Coffee Supply is the first specialty Vietnamese coffee company in the United States, and from its inception, Nguyen has amplified representation for Vietnamese coffee farmers. At the New York coffee convention in 2019, Nguyen Coffee Supply debuted Truegrit, their 100 percent single-origin robusta. They were the only roaster to do so.
“Probably 95 percent of the people who came up to us said, ‘I’ve actually never tried a single-origin robusta,’ ” Nguyen said. Even self-proclaimed “coffee snobs” confessed to Nguyen that they never knew robusta could taste this way.
Their glowing reviews fractured the industry’s long-lived narrative against robusta and signaled its potential to become a greater slice of the coffee market.
Haggar is optimistic that multiple beans will recalibrate coffee’s climate equation.
“Hopefully, we are going to end up with a more diversified offer of coffees from across four or five different species,” Haggar, the researcher, said. “Which will hopefully make coffee drinking more interesting — but also mean that we will have different sources of resilience to a changing climate.”