Scientists rediscover lost coffee species suited to a warmer climate

In dense tropical forests in Sierra Leone, scientists have rediscovered a coffee species not seen in the wild in decades — a plant they say may help secure the future of this valuable commodity that has been imperilled by climate change.

The researchers said on Monday that the species, Coffea stenophylla, possesses greater tolerance for higher temperatures than the Arabica coffee, which makes up 56 per cent of global production, and the robusta coffee that makes up 43 per cent. The researchers found stenophylla coffee also had a superior flavour, similar to Arabica.

Botanist Aaron Davis, who led the study published in the journal Nature Plants, said stenophylla was farmed in parts of West Africa and exported to Europe until the early 20th century before being abandoned as a crop after robusta's introduction.

Many farmers throughout the world's coffee-growing belt already are experiencing climate change's negative effects, an acute concern for the multibillion-dollar industry.

How the 3 coffee species compare

Arabica's flavor is rated as superior and brings higher prices than robusta, which is mainly used for instant coffee and coffee blends. But Arabica has limited resilience to climate change and research has shown its global production could fall by at least 50 per cent by mid-century.

Stenophylla grows at a mean annual temperature of 24.9 C — 1.9 degrees higher than robusta coffee and up to 6.8 C higher than Arabica coffee, the researchers said.

Botanist Aaron Davis looks at coffee cherries on a tree. He was part of a group of scientists that went on a search for wild Coffea stenophylla in 2018. (Reuters)

The stenophylla rediscovery, Davis said, may help in the "future-proofing" of a coffee industry that supports the economy of several tropical countries and provides livelihoods for more than 100 million farmers. There are 124 known coffee species, though Arabica and robusta dominate the market.

"The idea is that stenophylla could be used, with minimum domestication, as a high-value coffee for farmers in warmer climates," said Davis, head of coffee research at Britain's Royal Botanic Gardens, Kew.

"For the longer term, stenophylla provides us with an important resource for breeding a new generation of climate-resilient coffee crop plants, given that it possesses a great flavour and heat tolerance. If the historic reports of resistance to coffee leaf rust and drought tolerance are found to be correct, this would represent further useful assets for coffee plant breeding."

Leaf rust is a fungal disease that has devastated coffee crops in Central and South America.

The study included flavour assessments involving 18 coffee-tasting experts. Stenophylla was found to have a complex flavour profile, with natural sweetness, medium-high acidity, fruitiness and good "body" — the way it feels in the mouth.

How stenophylla was rediscovered

In December 2018, Davis and study co-authors Jeremy Haggar of the University of Greenwich and coffee development specialist Daniel Sarmu searched for stenophylla in the wild. They initially spotted a single plant in central Sierra Leone. About 140 kilometres (87 miles) away in southeastern Sierra Leone, they found a healthy wild stenophylla population.

"Both locations were thick tropical forest, but stenophylla tends to occur on drier, more open areas: ridges, slopes and rocky areas," Davis said.

The species is threatened with extinction amid large-scale deforestation in the three countries where it has been known to grow in the wild: Sierra Leone, Guinea and Ivory Coast. (E. Couturon/IRD/Reuters)

Stenophylla had not been seen in the wild in Sierra Leone since 1954 and anywhere since the 1980s in Ivory Coast, Davis said. A few examples were held in coffee research collections.

Davis said stenophylla is threatened with extinction amid large-scale deforestation in the three countries where it has been known to grow in the wild: Sierra Leone, Guinea and Ivory Coast.

Unlike the red and occasionally yellow fruit of Arabica and robusta plants, stenophylla's fruit are intense black. The coffee beans are inside the fruit.

"I think we're hugely optimistic for the future that stenophylla can bring," said Jeremy Torz, co-founder of the specialty coffee business Union Hand-Roasted Coffee in East London, where part of the taste-testing was held.