Within the context of accelerating and long-term climate change, it has become necessary to explore the potential of new species of coffee that are more resilient. Arabica alone does not have the climate resiliency required to keep up with climate change projections. Arabica is a cool-tropical plant, originating from the highlands (1,000–2,200 m) of Ethiopia and South Sudan and has an optimum mean (annual) temperature range of 18–22 °C.
On the other hand, we have Robusta, the second arm of the global coffee business. Robusta coffee is a predominately low-elevation species (50–1,500 m), occurring naturally across much of wet-tropical Africa and is adapted to higher mean (annual) temperatures of 24–26 °C or perhaps even higher to 30 °C. It is also resistant to the prevalent strains of coffee leaf rust. For these reasons, robusta is often mooted as the replacement species for Arabica under a scenario of increasing temperatures and declining and increasingly erratic rainfall. However, Robusta may require as much or more rainfall (soil moisture) as Arabica, relative to other climate variables and could be more temperature sensitive than previously supposed (≤16.2–24.1 °C under a revised estimate of optimal range).
There are over 120 coffee species in the world, but two are quickly emerging as potential alternative coffee species to Arabica and Robusta. While these species are promising, are they commercially viable and consumer-friendly? Read on to unravel the history and future of Liberica and Stenophylla, the most promising of the climate-resistant coffees.
Stenophylla: A New Hope
Commonly known as the lost species of coffee, Coffea stenophylla was first formally documented in Sierra Leone in the 18th century. While the species has a long history as a type of wild coffee, it largely disappeared from the coffee scene due to its low yield and small berries. Back in the 18th and 19th centuries, Stenophylla was cultivated across much of West Africa until it was usurped by the more profitable Robusta plants. Gradually, Stenophylla faded into obscurity.
Stenophylla is considered endangered in the wild, where it grows at low elevations and high tropical temperatures. Research from the past indicates that Stenophylla has a similar flavour profile to Arabica but sensory information regarding Stenophylla has not been published since the 1920s. Renewed interest in climate-resistant coffee reignited research into Stenophylla in the mid- to late-2010s when it was rediscovered in Sierra Leone in 2019.
Stenophylla balances fruity and floral flavours 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.
Liberica: An Obscure Favourite
Liberica is named after its country of origin- Liberia, West Africa. In the 1870s, Liberica was widely disseminated across West Africa, particularly in Liberia, Ghana, and Sierra Leone. It rose to prominence in Asia as a replacement for Arabica during the coffee rust pandemic at the end of the 19th century that obliterated coffee cultivation in South and Southeast Asia. Today, it’s most commonly grown and consumed in Southeast Asia. Liberica accounts for less than 1% of the global coffee trade but in countries like The Philippines, up to 70% of the coffee grown is Liberica.
Liberica coffee plants tower above the rest with a height of over 60ft or 20m. The height forces farmers to climb ladders to harvest or prune the plants to grow horizontally rather than vertically. To match its gigantic height, the leaves, berries, and beans from Liberica plants are also larger than the other coffee species.
Liberica is high-yielding and robust, growing at lowland elevations and resistant to many diseases. The cherries are often double the size of other coffee species, which means it has a lot of pulp. This poses some challenges with processing Liberica since it takes much longer to dry and often ferments in the process, giving it a distinct fruity flavour. The drying process needs to be carefully monitored to produce good flavour profiles. Errors in processing can negatively affect the final cup and the differences are very pronounced with Liberica. Natural processed Liberica is often described as having notes of jackfruit while washed Liberica has more citrusy and chocolate notes.
Stenophylla vs Liberica
Both Stenophylla and Liberica have emerged as popular potential alternatives to Arabica but we’re far from completely replacing specialty Arabica with other coffee species. Moreover, how do Stenophylla and Liberica compare to each other?
Both Stenophylla and Liberica have been traced back to Sierra Leone and both rose to prominence in the mid- to late 1800s. Stenophylla is considered ‘high land’ coffee whereas Liberica grows in the lowlands. Stenophylla plants are smaller than Liberica, with small leaves and large, round berries. Comparatively, Liberica is a towering plant with immense height and large leaves but small, firm berries with low sugar content and more caffeine.
Coming to flavour profiles, Stenophylla has been described as mild and earthy, like tea. On the other hand, Liberica is intense and bitter, making it well-suited for blends.
There are three main options available to adapt coffee farming for climate change:
(1) Shifting coffee cultivation to areas with suitable climates
(2) adapting coffee farming practices
(3) the development of new coffee crop plants.
Of these options, developing new coffee crop plants is likely to be the least disruptive and the most cost-effective. The idea of broadening the coffee crop portfolio, with new cultivars, hybrids and alternative species (including underutilized crop species) is receiving renewed attention with a focus on forgotten or underutilized species, particularly those that were once cultivated and exported at scale
In a changing climate landscape, Liberica offers the potential to grow commercially viable, and perhaps high-value, coffee under warmer temperatures and at lower elevations than Arabica and may offer improved resiliency over Robusta. Despite higher flavour quality in other underutilized species, particularly Stenophylla, Liberica offers almost ready-made crop options. The bean size of Stenophylla is similar to Arabica, but its productivity is lower and would require some development for commercial use.
The history of coffee farming demonstrates that underutilized species are only likely to come into major usage as a response to drastic disruptions in the supply chain. The introduction and scaling of Liberica, and then Robusta, was the response to the major devastation caused by the coffee leaf rust epidemic towards the end of the nineteenth century. Similarly, climate-related issues along with pest and disease problems can be agents for change in the coffee supply chain that leads to the re-emergence of alternate coffee crop species.
Ultimately, the profound impact of climate change on global coffee production is driving us towards being proactive in climate adaptation and demonstrates the need for alternative coffee species that are resilient to extreme climatic conditions. Liberica and Stenophylla coffee may provide part of the diversification required to achieve this objective.