Can Elevated Air [CO2] Conditions Mitigate the Predicted Warming Impact on the Quality of Coffee Bean?

Abstract

Climate changes, mostly related to high temperature, are predicted to have major negative impacts on coffee crop yield and bean quality. Recent studies revealed that elevated air [CO2] mitigates the impact of heat on leaf physiology. However, the extent of the interaction between elevated air [CO2] and heat on coffee bean quality was never addressed. In this study, the single and combined impacts of enhanced [CO2] and temperature in beans of Coffea arabica cv. Icatu were evaluated. Plants were grown at 380 or 700 μL CO2 L-1 air, and then submitted to a gradual temperature rise from 25°C up to 40°C during ca. 4 months. Fruits were harvested at 25°C, and in the ranges of 30–35 or 36–40°C, and bean physical and chemical attributes with potential implications on quality were then examined. These included: color, phenolic content, soluble solids, chlorogenic, caffeic and p-coumaric acids, caffeine, trigonelline, lipids, and minerals. Most of these parameters were mainly affected by temperature (although without a strong negative impact on bean quality), and only marginally, if at all, by elevated [CO2]. However, the [CO2] vs. temperature interaction strongly attenuated some of the negative impacts promoted by heat (e.g., total chlorogenic acids), thus maintaining the bean characteristics closer to those obtained under adequate temperature conditions (e.g., soluble solids, caffeic and p-coumaric acids, trigonelline, chroma, Hue angle, and color index), and increasing desirable features (acidity). Fatty acid and mineral pools remained quite stable, with only few modifications due to elevated air [CO2] (e.g., phosphorous) and/or heat. In conclusion, exposure to high temperature in the last stages of fruit maturation did not strongly depreciate bean quality, under the conditions of unrestricted water supply and moderate irradiance. Furthermore, the superimposition of elevated air [CO2] contributed to preserve bean quality by modifying and mitigating the heat impact on physical and chemical traits of coffee beans, which is clearly relevant in a context of predicted climate change and global warming scenarios.

Why could the coffee crop endure climate change and global warming to a greater extent than previously estimated?

“…The impacts of supra-optimal temperatures on coffee bean quality traits reported by Ramalho et al (2018) were lower than what are commonly observed in the field. Nevertheless, prevalence of high temperatures in the field often coincides with decreased water availability and high atmospheric VPD (compared to the controlled conditions in the study of Ramalho et al (2018)).…”

“…The impacts of supra-optimal temperatures on coffee bean quality traits reported by Ramalho et al (2018) were lower than what are commonly observed in the field. Nevertheless, prevalence of high temperatures in the field often coincides with decreased water availability and high atmospheric VPD (compared to the controlled conditions in the study of Ramalho et al (2018)). Given that water supply per se might affect coffee bean quality (Vinecky et al 2017), it is anticipated that a negative interaction between water supply and temperature could occur under field conditions, which would ultimately exacerbate impairments on coffee bean and beverage quality.…”

“…It is well known that elevated [CO 2 ] can impair the food quality of several crops (DaMatta et al 2010). However, in C. arabica plants grown in large (80 L) pots under controlled conditions (unlimited water supply), Ramalho et al (2018) observed that elevated [CO 2 ] per se did not promote noticeable changes in bean quality traits. Most importantly, enhanced [CO 2 ] remarkably altered the heat promoted patterns of variation on most physical and chemical bean traits in a way that would not be expected from the single effects of heat or [CO 2 ].…”

“…Among the observed impacts in fruits exposed to high temperature (30-40°C) in their final stages of maturation, elevated air [CO 2 ] increased acidity but decreased 5-caffeoylquinic acid (CQA) and caffeine, which all can be associated with an improved bean quality (Bertrand et al 2012). Additionally, elevated [CO 2 ] canceled (soluble solids, total CQAs, caffeic acid), attenuated (4-CQA, trigonelline), or reversed (pcoumaric acid) the biochemical modifications driven by heat (Ramalho et al 2018). Given these facts, it is tempting to suggest that enhanced [CO 2 ] can have the potential to modify and mitigate the heat impact on bean quality traits, that is, to keep bean composition, and concomitantly its quality, closer to the actual standards.…”

“…In this study, we summarize recent insights on the coffee performance at elevated [CO 2 ] in addition to reporting that an increase in air [CO 2 ] plays a significant role for the success of the coffee crop to endure environmental stresses, e.g., rising temperatures and drought due to climate change. These facets are examined by encompassing multiple plant levels, e.g., physiology (Martins et al 2014b(Martins et al , 2016DaMatta et al 2016;Rodrigues et al 2016;, plant structure (Rakočević and Matsunaga 2018;), bean quality traits (Ramalho et al 2018), and yields (this study). We conclude this review article pointing the gaps in our current knowledge on the coffee crop within the context of climate changes and highlights perspectives and research priority needed to advance our understanding on how this crop will respond to the present and ongoing climate changes.…”