Anthony King
A wild coffee from West Africa has surprised aficionados with its outstanding taste. The narrow-leaved species, Coffea stenophylla, grows in much warmer temperatures than either Arabica or Robusta coffee, so is more resilient to climate change.
‘Stenophylla tastes like Arabica, which tears up the rule book for great tasting coffee,’ says botanist Aaron Davis, at the Royal Botanic Gardens in Kew, London, UK. There are 124 species of coffee and Davis has tasted around 20 of them, an experience that had lowered his expectations for Stenophylla. ‘It tastes like Rwanda Arabica, which is just freaky.’
Arabica originated in cool highlands of Ethiopia and southern Sudan and grows best from 18 to 22°C. It makes up 56% of global production. Robusta (Coffea robusta) is not as sweet as Arabica and is used in instant coffee and espresso and priced lower. It makes up 43% of global production and is adapted to higher mean temperatures from 24 to 26°C. Both species are seen as under yield pressures due to climate change.
Higher temperatures are already impacting on Arabica yields in Africa, says Jarrod Kath, a climate scientist at the University of Southern Queensland, Australia. ‘We have done work in southeast Asia on Robusta coffee, which is supposed to be the tougher coffee, and that shows yields declining sharply as temperature increases.’
An assumed optimal temperature range of over 22°C is probably incorrect and overestimates Robusta’s ability to add to coffee production under climate change, this study concluded (Global Change Biology, doi: 10.1111/gcb.15097).
It is hard to imagine a world without Arabica, but we may have to, comments Emma Sage at the Coffee Quality Institute in Viejo, California, given our changing climate. ‘To find a coffee species that would thrive in future climates and has a highquality flavour is a ‘unicorn’ that Davis has shown here could go from myth to reality,’ she adds. ‘I hope to see much more analysis of this species moving forward – understanding the cultivation potential and economic viability of this plant will take a massive and coordinated effort.’
The latest research shows C. stenophylla grows at a mean annual temperature 6.2 to 6.8°C higher than Arabica coffee, and so is of interest as a climate-resilient coffee crop. There is also the potential to improve its characteristics. ‘The initial genetic analysis we’ve done shows that there’s a lot of genetic diversity, more so than Arabica,’ says Davis.
To find a coffee species that would thrive in future climates and has a high-quality flavour is a ‘unicorn’ that Davis has shown here could go from myth to reality. I hope to see much more analyses of this species moving forward – understanding the cultivation potential and economic viability of this plant will take a massive and coordinated effort. | Emma Sage at the Coffee Quality Institute, Viejo, California
‘It’s out there in Guinea, Sierra Leone and Ivory Coast. There’s more diversity and some of it could be extremely useful for the crop plant itself, but also for breeding,’ he adds, though the species is threatened with extinction in the wild.
Kath says ‘more research probably needs to be done before we can say that [Stenophylla] is viable as a crop.’ He too was surprised by the tasting results. ‘There has been an assumption that Arabica is the only high quality coffee species. For these guys to come along and show there’s another species out there, that performs as well as Arabica, is quite a big deal.’
Four panels and 15 judges evaluated Arabica, Robusta and Stenophylla coffee blind (Nature Plants, 2021, doi: 10.1038/s41477-021-00891-4). Asked if a sample was Arabica, 98% said yes for Arabica from Ethiopia and 88% for Stenophylla. The wild coffee was identified as something new by 47% of judges. Stenophylla had a complex flavour profile with natural sweetness, medium to high acidity, fruitiness and good body.
The species was rediscovered in late 2018 in a Sierra Leone forest by Davis and his team (Front. Plant Sci., 2020, 11, 616). It had been grown at scale up until the 1920s in Guinea, Sierra Leone and Ivory Coast, and exported to Europe as a high value coffee. There were anecdotal reports from 1834 that it tasted better than Arabica.
‘It has been this legendary species that baristas and coffee aficionados wanted to get their hands on and taste,’ says Davis. His team initially sought out small plantations, but Stenophylla was eventually rediscovered as an understory tree in dense hot forests, mainly confined to slopes, ridges and more rocky places.
It may take at least four years to get a Stenophylla crop in Sierra Leone, and Davis estimates it may be seven-to-ten years before small scale production emerges. ‘We didn’t have a heat-tolerant coffee that tasted great,’ he says. ‘Now we do.’
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