Commentary: The resilient coffee discovery that could save our morning brew

CNA

07-05-2025

LONDON: It was the yellowing label on an ancient jar of coffee beans tucked away in a herbarium that caught the eye of Aaron Davis, a botanist at the Royal Botanic Gardens at Kew. The label noted that the beans had been cultivated in the lowlands of Sierra Leone.
That stood out: coffee is usually a highland crop, favouring cool, moist conditions. The beans, labelled as coming from the species coffea stenophylla, physically resembled arabica beans, which account for about 60 per cent of the coffee drunk worldwide (the rest is mostly robusta, a less flavoursome species that is resistant to coffee leaf rust and used mostly for instant coffee).
A trawl of old books and journals returned sepia photographs of stenophylla plants growing alongside hot-climate plants. And, tantalisingly, notes from 19th century collectors described a delicious arabica-like flavour.
As the Smithsonian magazine reports, this rediscovered plant, rare in the wild but under experimental cultivation in Sierra Leone, might have a role to play in shoring up coffee supplies – and saving farmers' livelihoods – in the face of climate change, drought and disease.
According to a paper published in March, stenophylla is also the first coffee bean reported to contain theacrine, a caffeine-like substance popularly thought to lack some of caffeine's downsides. The message is as strong as a double espresso: biodiversity matters and, when we lose species, we lose options for the future.
Coffee beans are not really beans at all but the seeds found inside the fruit, called coffee cherries, of the coffea plant. These seeds are harvested, dried and roasted into the beans that give us our daily brew.
Globally, an estimated 3 billion cups of coffee are sipped every day, with the habit on the rise among the growing middle-class, especially in China and parts of Africa.
But every cup begins with a crop – and climate change is putting pressure on supply, with prices reaching historic highs in recent months. Heat, drought and erratic rainfall in key growing countries like Brazil, Vietnam and Colombia spell weak and unpredictable harvests – and precarious incomes for smallholder farmers, who grow the bulk of the world's supply.
MORE SUSTAINABLE TO FIND NEW OPTIONS
While one solution is to shift production geographically as the climate changes, people like Davis, head of coffee research at Kew, and longtime collaborator Jeremy Haggar of the University of Greenwich, think a more sustainable answer is to diversify into climate-resilient choices among the 131 coffee species identified so far.
The two most exciting new species on the block, Davis told me, are excelsa and stenophylla.
Excelsa has a deeper root system, allowing access to water in drought conditions, and is also resistant to heat, pests and disease. The first coffee from a Ugandan excelsa project that he has been involved in will come to the UK market this year (he reports the smooth taste to be comparable to a speciality arabica).
Stenophylla is at a more experimental stage. In 2018, Davis and Haggar managed to track down the plant in Sierra Leone with the help of Daniel Sarmu, a coffee specialist in the country.
Together with the coffee company Sucafina, the non-governmental organisation Welthungerhilfe and the co-operation of local communities, the trio have planted wild varieties in trial plots across Sierra Leone with a view to reviving it as a coffee crop (its prospects withered in the mid-20th century as local farmers turned to robusta). The first harvest is expected this year.
EXCITING POSSIBILITIES
Importantly, stenophylla upends the wisdom that posh coffee is arabica grown at elevation in the cool tropics. 'To have something that produces an almost indistinguishable flavour profile but grows in warmer places is so exciting,' Davis says.
The species can withstand hotter conditions than excelsa, up to 6 or 7 degrees Celsius higher than arabica – and, against expectation, most of the Sierra Leone plants survived a heatwave last year. The growing conditions – temperature, humidity, soil moisture – have been meticulously documented, and will allow researchers to select plants with favourable climate resilience, yield and disease resistance.
Stenophylla, also native to Ivory Coast and Guinea, could become a high-value coffee in itself – as well as a critical tool for breeding, lessening reliance on climate-sensitive arabica. The Sierra Leone project is also experimenting with grafting stenophylla on to excelsa rootstock.
Davis and colleagues have been flooded with requests for stenophylla plants but ownership rights, he explains, rest with national governments. Protecting biodiversity is not just for the soft-hearted, one might wager, but also for the hard-nosed.