Millions of people around the world enjoy a daily cup of coffee; however, their daily caffeine fix could be under threat because climate change is killing coffee plants, putting farmers' livelihoods at risk.
Inside the vast, steamy greenhouses at the Royal Botanic Gardens at Kew in the leafy suburbs of west London, Aaron Davis leads the research into coffee.
"Arabica coffee, our preferred coffee, provides us with about 60% of the coffee that we drink globally. It's a delicious coffee, it's the one we love to drink. The other species is robusta coffee, which provides us with the other 40% of the coffee we drink – but that mainly goes into instant coffees and espresso mixes," Davis explains.
The cultivation of arabica and robusta coffee beans accounts for millions of livelihoods across Africa, South America and Asia.
"These coffees have served us very well for many centuries, but under climate change they're facing problems," Davis says.
"Arabica is a cool tropical plant; it doesn't like high temperatures. Robusta is a plant that likes even moist conditions; it likes high rainfall. And under climate change, rainfall patters are being modified, and it's also experiencing problems. In some cases, yields are dramatically reduced because of increased temperatures or reduced rainfall. But in some cases, as we've seen in Ethiopia, you might get a complete harvest failure and death of the trees."
The solution could be growing deep in the forests of West Africa. There are around 130 species of coffee plant – but not all taste good. In Sierra Leone, scientists from Kew helped to identify one candidate, stenophylla, growing in the wild.
"This is extremely heat tolerant. And is an interesting species because it matches arabica in terms of its superb taste," Davis says.
Two other coffee species also show promise for commercial cultivation in a changing climate: liberica and eugenioides, which "has low yields and very small beans, but it has an amazing taste," according to Davis.
Some believe the taste is far superior. At the 2021 World Barista Championship in Milan, Australia's Hugh Kelly won third prize with his eugenioides espresso. Kelly recalled the first time he tasted it at a remote farm in Colombia. "It was a coffee like I've never tasted before; as I tasted it, it was unbelievably sweet … I knew that sweetness and gentle acidity were the bones for an incredible espresso," Kelly told judges in Milan.
Researchers hope Kelly's success could be the breakthrough moment for these relatively unknown beans.
The team at the Botanic Gardens is working with farmers in Africa on cultivating the new coffees commercially. Catherine Kiwuka of the Ugandan National Agricultural Research Organization, who oversees some of the projects, says challenges still lie ahead.
"What requirements do they need? How do we boost its productivity? Instead of it being dominated by only two species, we have the opportunity to tap into the value of other coffee species."
It's hoped that substantial volumes of liberica coffee will be exported from Uganda to Europe this year. Researchers hope it will provide a sustainable income for farmers – and an exciting new taste for coffee drinkers.