Climate Change, Coffee Quandry: What We Know (and Need to Know) About Climate Change’s Impact on Coffee Quality | 25, Issue 17
Corresponding author Dr. SELENA AHMED outlines the findings of a systematic review of research conducted to better understand climate change’s impact on coffee quality, what prompted the review, and what we need to research next.
When Dr. Selena Ahmed was nominated to speak at the 2018 Re:co Symposium, she was introduced as “someone doing work on climate change and tea that the coffee industry should be paying attention to.” In her research with tea producers in China, Dr. Ahmed established that a decline in key flavor compounds in their tea was associated with increasing variability in the Yunnan region’s monsoon season—one manifestation of climate change in the region—and the altered flavor profile had negative economic impacts for tea producers. The research also offered some hope: evidence indicated that tea grown in agroforests was less vulnerable to the changes the region’s producers were experiencing, and those shade systems offered additional environmental and economic benefits to farmers.
Anyone who heard her presentation in Seattle or read her article in Issue 4 of 25 would have immediately wondered whether the same logic would apply to coffee quality, and in the article, Dr. Ahmed recalls feeling eager to embed herself in coffee-growing communities, as she had done with tea producers, to investigate the similarities and differences between the two crops. Though she was new to coffee, she was an experienced researcher who knew well that her first step would have to be to understand the research that had been done by others on the subject and find the gaps, not to rush out to build a project of her own. For the past four years, spurred by the anecdotal evidence shared in the hallways and discussion rooms of Re:co, Dr. Ahmed has been leading a research team to conduct a literature review that will help the coffee sector answer the question: What should we do?
As is often the case with complex questions about sustainability, there is no single answer that will apply equally to everyone, everywhere coffee grows (spoiler alert: the answer is not to move coffee production to latitudes further from the equator). Readers of the study are likely to find some of their assumptions and anecdotal experiences reinforced by evidence, while other ideas will be challenged. As is always the case with research, this study revealed gaps in what we thought we knew—gaps that call for more research. And while it does not tell us exactly what to do to mitigate the negative effects of climate change on coffee plants, coffee flavor, and coffee growers, it tells us what we know based on all the work that has been done to date across the many regions of the world where coffee grows. By establishing a common foundation for our understanding, this work will make it easier for us to do everything we must, should, and can do.
Kim Elena Ionescu
Chief Sustainability and Knowledge Development Officer
“It has changed. The taste has changed.”
As I listened to coffee producers and buyers reflect on their experiences with climate change at the Re:co Symposium event in Seattle in 2018, I was reminded of these words, which I heard spoken by a smallholder tea producer from China’s Yunnan Province more than a decade earlier. I had just finished presenting my long-term research on climate effects on tea quality, and delegates were approaching me to share their experiences with coffee quality. I scribbled notes about their observations—increasing temperatures were reducing coffee sweetness, increasing rain was resulting in decreased quality—and their speculation that moving coffee to cooler altitudes could enhance production. The seed of inspiration had been gifted, and I wanted to know more: How was climate change impacting coffee quality? Were the berry, citrus, and chocolate notes that I so appreciate in coffee shifting? What could the coffee sector do to mitigate these impacts?
These are the questions of a coffee lover, and I immediately began imagining myself visiting coffee farms to document smallholder farmer experiences as I have done for tea gardens. I dreamt of awakening near shade-grown coffee farms, delighting in the sounds of the morning bird chorus, and learning from stewards of these ecological and agricultural systems. I began to research field sites, including those I had previously visited as a traveler, where I could gather coffee samples to bring back to my lab for measuring phytochemicals. But of course, I am not the first scientist drawn to exploring climate effects on coffee quality, and as a researcher I recognized the first question had to be: what do we know about climate change, management, and coffee quality based on the scientific evidence? I didn’t want to replicate work that had already been done; it was important to understand what gaps currently existed before proceeding to the field.
To answer my research question, I assembled a research team with members hailing from Montana State University’s Sustainable Food Systems Program (Food and Health Lab), Tufts University’s Friedman School of Nutrition Science and Policy, Texas A&M University’s Center for Coffee Research and Education, Treeline Coffee Roasters, and the Specialty Coffee Association (SCA). Each entity, and every individual on the team, brought a different perspective across academia and the coffee industry and day-to-day interactions with coffee consumers: agricultural economics, biochemistry, food composition analysis, plant sciences, nutrition science, policy, sensory analysis, sustainable food systems, coffee sourcing and roasting, brewing technology, marketing, and hospitality.
It was clear to us from the beginning of our project that the specialty coffee industry was already aware of climate change and eager to understand its effects on coffee quality, and not just for the sake of stimulating intellectual curiosity: coffee agriculture supports the livelihoods of the millions of smallholder coffee farmers across over 50 countries; coffee quality impacts the billions of coffee consumers who value the aroma and taste of their daily cups and helps determine how much they are willing to pay for their beans and brew.
The “coffee belt” of regions suitable for coffee cultivation is situated in areas that are increasingly vulnerable to shifting climate conditions—conditions that have implications for coffee’s taste, aroma, health attributes, and productivity, and ultimately underpin the economic viability, stability, and sustainability of the entire coffee sector. But while industry actors representing every link in the value chain, from the largest companies to the smallest, agreed that climate change threatens coffee and that adaptation is important, the sector lacked a scientific understanding of how it has affected coffee agriculture or what should be done about it, relying instead on experiences at the micro level (like a single farm or community) and macro level (national and even global trends). In addition to revealing gaps that would warrant further research, we believed this literature review would also serve the industry as it sought to differentiate between documented evidence and speculation.
A Systematic Review
Professor Sean Cash (Friedman School of Nutrition Science and Policy at Tufts University) and I led our collaborative group of academia and industry incarrying out a systematic literature review with the goal to precisely describe the totality of scientific evidence on the effects of climate change on coffee quality. As climate change is a long-term process with limited studies, we focused on examining the environmental factors linked to climate change, such as temperature and rainfall. Additionally, we examined the management factors linked to climate adaptation: for example, the application of pesticides and use of shade trees to mitigate climate risk.
To carry out the systematic review, we identified and refined key terms that best reflected our research question. We then input these key terms into multiple search engines in scientific literature databases, a process that yielded 2,641 articles. After gathering all the evidence, we assessed each of them to see which ones addressed our overall research question. We had multiple reviewers on our team sort through each article to remove any researcher bias, so that anyone else carrying out the literature review would retrieve the same articles. From the more than 2,000 articles the search returned, we identified 73 published studies in the scientific literature that addressed our overall research question on environmental and management effects on coffee quality.
These studies made it clear that the coffee plant, like the tea plant, is an indicator species of climate change, which means that it reflects the environmental conditions around it. The scientific evidence highlighted that indeed coffee phytochemicals, including the phenolics, terpenoids, and alkaloids—and the flavors associated with these compounds—are sensitive to shifts in environmental factors linked to climate change.
If coffee is sensitive to many shifts, which shifts are the most impactful? We found the most consistent evidence across studies regarding impacts of altitude and light exposure on coffee quality. Increased altitude, which serves as a proxy measure for decreased temperature, was associated with increased coffee sensory attributes based on aroma and taste. Additionally, we found that increased light exposure is associated with decreased coffee sensory attributes based on aroma and taste. This may not come as a surprise to producers and buyers who for decades have espoused growing coffee under a canopy of shade trees—reducing light exposure—for both the environmental benefits and the boost to cup quality. But documenting these effects is important to driving future investments effectively. And while positive sensory attributes are valuable (including in monetary terms), it is important to note that while there was a consistent impact on perceived sensory attributes, it didn’t correspond consistently with phytochemical measurements.
In the case of other environmental factors, the impacts on quality were much less clear and bigger research gaps remain to be filled. Very few studies were found tracing the impact of carbon dioxide on coffee. Also, while the evidence is clear that coffee quality is vulnerable to increased temperature and water stress, the few papers that did try to link these conditions to specific phytochemicals and sensory attributes didn’t agree: some studies indicated that water stress has positive effects on cup quality; others, the opposite. These divergent conclusions may result from inconsistencies in the design of the experiments, but it may also reflect the diversity of the growing conditions and farming systems. To put it another way, it’s highly possible that certain management techniques will work well to mitigate climate risks for some farms and not have the desired effect for others. The studies reviewed further highlight that geography, nutrient management, pests and disease, and fruit thinning impact coffee quality, but we were unable to make comparisons between studies to identify desirable variables because of a lack of standardized experimental design between studies. Further refinement of and alignment around the methods used to evaluate sensory attributes will be important for identifying the environmental factors that pose the greatest risks and the management factors that offer the greatest opportunities to specialty coffee stakeholders.
What Next?
While our systematic review highlights the benefits of increased altitude for coffee quality, moving coffee farms to higher elevations is not a globally viable option for managing and mitigating climate risk, particularly for vulnerable smallholder farmers who are unable to acquire new lands and whose cultural identity is linked to the landscape. Creating farms at higher elevations also poses threats to biodiversity in areas where forests need to be converted for agriculture. Innovative solutions need to be identified at all elevations for coffee production that take into consideration the resources of producers. Among the most promising solutions for climate resilience is diversifying coffee farms to enhance shade—in addition to benefiting coffee quality by decreasing light exposure, it also offers multiple benefits in terms of farm (and value chain) sustainability. For example, numerous studies highlight the benefits of shade-grown coffee farms as a habitat for over 200 bird species. Beyond shade, the selection and maintenance of climate-resilient coffee cultivars, the incorporation of wild coffee germplasm, integrated pest management, soil nutrient management, and innovations in processing and brewing show promise for mitigating the effects of climate change on coffee quality.
Based on what we have learned (and what gaps remain), if the coffee sector wants to precisely understand the effects of climate change on coffee quality, we will need long-term research built on standardized experimental design and protocols for measuring coffee phytochemicals in diverse coffee-growing geographies, at a variety of elevations, and using many types of management systems. Given the pressing need for standardized ways to measure coffee phytochemicals to allow for understanding of the factors that drive phytochemical variation, and food composition more broadly, I am currently serving as Global Director of the Periodic Table of Food Initiative to develop and democratize such standardized technology and an open-access data platform. As coffee plants exist in complex systems of interacting environmental and management variables, future research needs to examine these interactive effects through both on-farm research and controlled experiments. Evidence from such research in different geographies is critical for informing the design of coffee farms that maintain or even improve coffee quality in the context of global change and support smallholder coffee farmers, including the most vulnerable. We further need to understand the barriers and opportunities that different climate adaptation strategies will encounter from different stakeholder groups in the coffee sector. These barriers include (but are not limited to) the willingness and capacity of producers to adapt based on their access to economic resources, land access, ecological knowledge, and social networks.
While climate poses risks to the taste and aroma of coffee, the process of initiating and conducting this research—beginning with the eagerness and earnestness of those first conversations in Seattle—has reinforced my hope that the coffee sector will come together to continue researching the impacts of climate change on coffee quality, and to act both individually and collectively to address this pressing issue. I have already seen global collective action in the tea sector to mitigate climate change. Together, we can strengthen the coffee sector from shocks through an evidence-based approach that honors biological and cultural diversity. ◇
Dr. SELENA AHMED is Global Director of the Periodic Table of Food Initiative and Associate Professor of Sustainable Food Systems at Montana State University.
The paper upon which this feature is based, “Climate Change and Coffee Quality: Systematic Review on the Effects of Environmental and Management Variation on Secondary Metabolites and Sensory Attributes of Coffea arabica and Coffea canephora,” was published in Frontiers in Plant Science in October 2021 by Ahmed, S.; Brinkley, S.; Smith, E. M.; Sela, A.; Theisen, M.; Thibodeau, C.; Warne, T.; Anderson, E.; Van Dusen, N.; Giuliano, P.; Ionescu, K. E.; and Cash, S. B.
Read the full systematic review: https://doi.org/10.3389/fpls.2021.708013.
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