Arabica coffee can't adapt to climate change. Production is plummeting? Carbon dioxide may be the savior.

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At the end of last year, the United Nations Climate change Panel (IPCC) published a major research report "Global warming of 1.5C", which solemnly warned that global warming would exceed 1.5° C between 2030 and 2053 if countries did not reduce carbon dioxide emissions as soon as possible. However, US President Donald Trump has repeatedly denied climate change, the progress of the Paris agreement is still slow, and the general signs are that global warming and extreme weather will disturb daily life more frequently in the foreseeable future.

(global warming 1.5 °C IPCC Special report, https: / / www.ipcc.ch/sr15/)

Arabica coffee (Coffea arabica), as we know it, is considered to be one of the species that are extremely sensitive to climate change. For example, coffee leaf rust hit Central America in 2010-2014, and Brazil's production fell sharply in 2014 due to drought. A well-known scientific study in 2015 even predicted that Arabica coffee could no longer be cultivated in more than 56% of the producing areas in the future (2050). 2] The sharp decline in production will inevitably lead to a rise in prices. Will a cup of coffee a day be the norm of life, or will it become a luxury but can not quit the habit? However, the latest research on coffee physiology points out that we don't need to be so pessimistic, and coffee may be more resilient than previously predicted.

Climate and Pest-driven Geographic shift in Global Coffee production, DOI:10.1371 / journal.pone.0133071

Carbon dioxide is actually fertilizer!

Carbon dioxide (CO2) + water (H2O) → glucose (glucose) + oxygen (O2)

If you have a superficial understanding of photosynthesis, you should be familiar with the above chemical reaction formula. Carbon dioxide, the reactant on the left, is the raw material of photosynthesis. if you increase the concentration of carbon dioxide in the environment, it can usually promote photosynthesis. and then get more glucose, that is, higher production. In the field of agriculture, this artificial practice is called carbon dioxide fertilization (CO2 fertilization).

Compared with many tropical fruit trees, the photosynthesis rate of coffee leaves (4-11 μ molCO2 ·m-1 ·s-1) is relatively slow [3]. However, under the best light and temperature, carbon dioxide fertilization can significantly increase the photosynthetic rate (30 μ molCO2 ·m-1 ·s-1) [4]. The rate difference of several times suggests that coffee has great potential in the future when the concentration of carbon dioxide in the atmosphere rises sharply.

A series of studies on photosynthesis have shown that in high carbon dioxide environment, many positive indicators of coffee are significantly improved, such as RuBisCO, the key enzyme of photosynthesis, electron transport chain (Thylakoid electron transport) [6] and stomatal conductance (Stomatal conductance) [7], while negative indicators are decreased, such as photorespiration (Photorespiration) [5] and active oxygen concentration ROS (Reactive oxygen species). However, is the effect of carbon dioxide fertilization endless or a flash in the pan?

Plant cells are like a factory, where large quantities of cheap raw materials (carbon dioxide) often increase production capacity, but when the warehouse is full and can no longer hold more goods (glucose, etc.), the production line also has to slow down. This common phenomenon is called negative photosynthesis regulation (Downregulation), but coffee seems to be an exception.

Several studies have pointed out that no significant negative regulation was observed in coffee whether in closed growth boxes or in open field facilities for carbon dioxide fertilization (Free-air CO2 enrichment; FACE). After four years of vertical FACE experiment, the photosynthetic cooperation rate of coffee trees with carbon dioxide fertilization was still 50% higher than that of the control group without fertilization [7]. Another FACE experiment showed a 28% increase in actual coffee production [8], much higher than the average of 17% for other crops [9]. The life cycle of leaves (leaf retention) and the accumulated heat needed for new leaf growth (the thermal time of leaf expansion) are also prolonged [10]. After reading this positive scientific evidence, we may be able to catch our breath, but don't forget that the heat caused by global warming is the worst enemy of coffee.

It is not only a fertilizer but also a specific medicine against high temperature stress.

Coffee is native to the cool Ethiopian plateau. From the perspective of cultivation experience and academic research, coffee is a crop sensitive to high temperature. Studies have shown that the development of flowers in coffee is poor at 28 °C, while that at 33 °C accelerates the aging and fall of leaves [11]. When it exceeds 34 °C, photosynthesis almost stops [12], resulting in flower deformities and inability to bear fruit, directly returning coffee production to zero. Some studies have also pointed out that high temperature will reduce the quality of coffee cups [13].

However, new scientific evidence suggests that high concentrations of carbon dioxide help coffee resist high temperature stress, including better photosynthesis and better raw bean quality. Under the high temperature of 37 / 30 ○ / ℃, high concentration of carbon dioxide can help coffee maintain good photosynthesis, and leaf life is not affected by high temperature, although there is still a high proportion of abnormal flowers [14] high temperature has negative effects on the chemical composition of raw beans, including lower soluble sugars, higher total chlorogenic acid and caffeic acid, the new study also pointed out that high concentration of carbon dioxide The negative effects of these high temperatures can be eliminated or even reversed [15]. It means that the early high temperature research, which did not take into account the soothing effect of carbon dioxide, is the future of high carbon dioxide, and it is likely that all the things we worried about before will not happen.

Why is carbon dioxide so powerful? the researchers put forward several possibilities: 1. High carbon dioxide can inhibit photorespiration, inhibit the production of free radicals, and help leaves to normal photosynthesis 0.2. The ripening rate of seeds (raw beans) at high temperature can not keep up with the ripening speed of pulp, which leads to deformities or insufficient plumpness of raw beans. Perhaps the increased photosynthesis caused by high carbon dioxide more or less makes up for the gap in nutrient demand of raw beans at high temperature.

Pixabay.com

The new model has a more optimistic prediction.

Traditionally, places with an average annual temperature of more than 23 ℃ are considered unsuitable for coffee cultivation, but in recent years, with the progress of cultivation techniques, through correct fertilization, pruning, yield control and shade management, many places with an average temperature of 25 °C can also produce coffee stably, new varieties with Robsta (C. canephora) gene can even adapt to higher temperatures. The previous coffee production area change model predicted that more than 56% of the current coffee producing areas would no longer be able to cultivate Arabica coffee in 2050. This pessimistic prediction may be due to the fact that this study refers to current climatic data in producing areas to make assumptions suitable for the growing environment, without taking into account the adaptability of new varieties, high carbon dioxide and new cultivation methods.

In recent years, new models of cultivation change in coffee producing areas of Uganda, Tanzania and Brazil have referred to new scientific evidence, pointing out that increased carbon dioxide concentrations may partially or even completely offset the negative effects of high temperature. without a large-scale reduction in production [17] [18], however, there is still a lot of room for progress in these predictions, and no one dares to assert the future of the coffee industry.

The Sustainable Future of Coffee

Many scientific evidence points out that high carbon dioxide concentration can make coffee have better photosynthesis and growth, offset the negative effects of high temperature, and even have a soothing effect on drought stress. After considering the above research results, the new model has a more optimistic prediction.

In order to continue to enjoy this cup of coffee in our hands in the future, the world needs more solid academic research and variety research in order to see clearly and face the future of global warming and help coffee find a sustainable way out.

The original text is translated in C3 Coffee Journal Vol. 18,2019

Notes

Main references

DaMatta,FM,Rahn,E.,L ä derach,P.,Ghini,R. , & Ramalho,JC (2018). Why coffee crops can withstand climate change and global warming to a greater extent than previously estimated. Climate change, 1-12.

Secondary references

1. IPCC . (2018). Special report-Global warming 1.5 °C. "https://www.ipcc.ch/sr15/"

2. Magrach,A . , & Ghazoul,J. (2015). Climate and pest-driven geographical changes in global coffee production: impacts on forest cover, biodiversity and carbon storage. PLoS One,10 (7), e0133071.

3. Ecophysiological limitations of DaMatta FM (2004) on shaded and unshadowed coffee production: a review. Field Crop Res 86:99-11400

4. Martins SVC et al. (2014) understand the low photosynthetic rate of sun and shadow coffee leaves: bridging the gap in the relative effects of hydraulic, diffusion and biochemical restrictions on photosynthesis. PLoS One 9:e95571

5. DaMatta FM et al. (2016) continuously enhanced the photosynthesis of coffee trees grown in free air CO2 concentration: the contribution of stomatal, mesophyll and biochemical limitations. J Exp Bot 167VR 341-352

6. Ramalho JC et al. (2013) Coffea spp. The sustained photosynthetic performance. In the long-term enhancement [CO2]. PLoS One 8:e82712

7.Rako "evi" M Ribeiro RV,Marchiori PER,Filizola HF,Batista ER (2018) structural and functional changes of coffee trees after 4 years of free air CO2 concentration. Ann Bot 21R 1065-1078

8. Ghini R et al. (2015) response of coffee growth, pests and yield to free air CO2 concentration. Clim Chang 132Rank 307-320

9. Ainsworth EA,Long SP (2005) what have we learned from 15 years of free air CO2 enrichment (FACE)? A meta-analysis review of the responses of photosynthesis, canopy characteristics, and plant production to CO2 rise. New Phytol 165Drex 351-372,

10.Rako "evi" M. Matsunaga FT (2018) the relationship between the changes of leaf growth parameters and seasonal growth, water supply and air carbon dioxide concentration in the structure of adult small-grain coffee tree. Ann Bot 122 purl 117-131

11. Drinnan JE,Menzel CM (1995) during flowering, temperature affected the vegetative growth and flowering of coffee (Coffea arabica L.) after water stress. J Hort Sci 70:25-34

12. Nunes MA,Bierhuizen JF,Ploegman C (1968) study on coffee productivity. i. Effects of light, temperature and CO2 concentration on photosynthesis of small-grain coffee. Acta Bot Neerl 17:93-102,

13. DaMatta FM,Cavatte PC,Martins SCV (2012) Coffee Physiology: growth, yield and quality. In: Oberth ü rt, L ä derachP,Pohlan HAJ,Cock JH (Editor) featured Coffee: management quality. International Plant Nutrition Institute,Norcross,Georgia,USA,pp 75-91

14. Rodrigues WP et al. (2016) long-term elevated air [CO2] enhanced photosynthetic function and reduced the effect of super-optimal temperature of tropical small-grain coffee and C. canephora species. Glob Chang Biol 2215-431

15. Ramalho JC et al. (2018) can increased air [CO2] conditions mitigate the impact of predicted warming on the quality of coffee beans? Front Plant Sci 9: art 287

16. Rahn E et al. (2018) used process-based models to explore adaptation strategies for coffee production to climate change. Ecol Model 371 rig 76-89

17. Verhage FYF,Anten NPR,Sentelhas PC (2017) carbon dioxide fertilization offset the negative impact of climate change on Arabica coffee production in Brazil. Clim Chang 144VR 671-685

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