By Rachel Chan
Coffee is the world’s favourite beverage. From the 2.25 billion cups of coffee consumed everyday to the 100 million people whose livelihoods depend on it (Davis et al., 2019), coffee has found its way into many of our lives. Unfortunately, there remain a multitude of threats to the coffee sector; these are mainly brought on by climate change, particularly the increase in incidence and duration of drought and the emergence and/or spread of coffee pathogens and pests.
Shrubs of the genus Coffea produce berries whose seeds are processed to become the coffee beans we know and love. World coffee trade comes from two species of Coffea: C. arabica (Arabica) and C. canephora (Robusta), which are responsible for 99% of world coffee production (Bunn, Läderach, Ovalle Rivera and Kirschke, 2014). Generally, the quality of Robusta coffee is considered to be inferior to that of Arabica. Both species thrive under different, specific conditions but are considered to be highly climate-sensitive – hence the major threat posed by climate change. Furthermore, the lifespan of a coffee plantation is 30 years, making future warming even more of a concern, as current plantations are likely to experience the forecasted future climate variations (Bunn, Läderach, Ovalle Rivera and Kirschke, 2014).
The optimum mean annual temperature for Arabica is 18-21°C and it is grown best at higher altitudes. Temperatures upwards of 23°C lead to a loss of beverage quality, due to the sped up ripening of fruits (Davis, Gole, Baena and Moat, 2012). Additionally, Arabica has requirements related to frost probability and water availability, so it is mostly grown in Latin America, Eastern Africa and Brazil. The optimum mean temperature for Robusta is 22-26°C and requires a lack of intra-seasonal variability- it is cultivated in Brazil, Central Africa and Southeast Asia (International Coffee Organization – Botanical Aspects, 2020). Since C. arabica and C. canephora differ in their optimal growing conditions, climate change is projected to affect both of them differently. C. canephora is more heat tolerant and more pest resistant than C. arabica, while C. canephora is more susceptible to low temperatures (Davis et al., 2019).
The Intergovernmental Panel on Climate Change predicts that the average global increase in temperatures will be between 1.8-4°C by the end of this century. In the last 100 years, global temperatures have increased by an average of 0.74°C (IPCC, 2007). Common markers of climate change are widespread drought in some regions and extensive flooding in others (Jaramillo et al., 2011). Coffee farmers and coffee sector stakeholders have already reported that production has been negatively impacted by changes in climate. For Arabica production in Eastern Africa, this is mainly due to uncertainty of precipitation variability and an extension of the dry season (Moat et al., 2017). Changes like this make it hard to sustain a livelihood from growing coffee.
Changes in climate also affect coffee crops indirectly through agricultural pests. Temperature has a strong influence on insect development, reproduction and survival. In the last 30 years, climate change has already shifted the distribution and abundance of certain species, and has impacted agricultural production (Jaramillo et al., 2011). Hypothenemus hampei, the coffee berry borer, is the most significant biotic constraint for coffee production worldwide. Adult females bore holes in the coffee berry, where eggs are deposited. Upon hatching, larvae feed on the coffee seeds inside the berry, reducing its yield and quality (Infante, Jaramillo, Castillo and Vega, 2009). In 2001, there were no reports of H. hampei attacking coffee plantations above 1500 metres (within the optimal altitude range for C. arabica), suggesting that the original host of the coffee borer was C. canephora (Infante, Jaramillo, Castillo and Vega, 2009). However, due to increasing temperatures, changes in the altitudinal range of H. hampei now make global Arabica coffee production more susceptible to the pest.
Sadly, coffee isn’t safe from pathogens either- coffee production is being compromised by the spread and rising severity of fungal pathogens; in particular, coffee rust for Arabica in South America and coffee wilt disease for Robusta in Africa (Davis et al., 2019). In the case of coffee rust epidemics, a common factor has been irregularities in temperatures, with higher minimum and lower maximum temperatures experienced daily (Avelino et al., 2015). It’s clear that these epidemics have been exacerbated by weather conditions consistent with climate change.
With climatic risks threatening to only escalate in the near future, interests have been shifted towards breeding more resilient crops. Wild variants of C. arabica and C. canephora are of most importance, but other wild coffee species are likely to be required as well. There are 124 known coffee species and several noncommercial species have even been used on a local scale as a substitute for Arabica coffee (Davis et al., 2019). These species have traits that could prove useful for the future of coffee, such as drought tolerance and pest and disease resistance. Wild species of coffee are critical for the sustainability of the coffee sector, but their future doesn’t look too promising either. At least 60% of coffee species are threatened with extinction, with wild coffee variants of priority included within this (Davis et al., 2019).
Nonetheless, adaptive measures like this are coffee’s best bet and the coffee sector have efficiently responded. Coffee-dependent governments in Latin America are investing in research to breed more resilient plants and small-scale farmers are planting large trees to shade coffee plants.
The verdict: by 2050, climate change will reduce the global area suitable for coffee cultivation by about 50% across emission scenarios (Bunn, Läderach, Ovalle Rivera and Kirschke, 2014). As expected, climate change will greatly reduce the production of Arabica coffee, especially in Brazil. Coffee could perhaps be cultivated at higher altitudes, but this does not serve current producers and could threaten ecosystems. While Robusta is more heat tolerant, the hope that it could replace Arabica is dampened by the fact that Robusta requires little interseasonal variability; something climate change may not allow for. Furthermore, two major regions of Robusta production, Vietnam and Brazil, are also predicted to be less suitable for Robusta cultivation (Bunn, Läderach, Ovalle Rivera and Kirschke, 2014). All in all, the gains miserably fail to make up for the losses.
Given these factors and projections, the coffee sector’s future is looking quite bitter. Tasteless pun aside, this brings about many questions on what the coffee sector will look like. For the consumer, coffee prices could increase due to dwindling production, quality might change and choices may be more limited. For the smallholder farmers that produce 80% of the world’s coffee, the future of coffee threatens their incomes. While we grapple with the loss of our favourite specialty Arabica coffee, smallholder farmers will be mourning their livelihoods.
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