Climate change is now carrying a significant portion of promises in global weather, as rising atmospheric vapour pressure deficit (VPD) has become one of the most important aspects of change in atmospheric behavior. VPD acts as an important parameter of plant stress, indicating the difference in vapour pressure between saturated air and the actual vapour pressure of the surrounding air. VPD has been shown to increase globally with rising temperatures, and the pace of this increase would be accelerating soon in the decade to come. With an increase in VPD, great concern arises about its consequences on the ecosystem and agricultural systems, including coffee production.
The coffee plant thrives on environmental conditions under which these parameters function. When VPD begins to change, it has very great consequences on the plant. The interaction between VPD and temperature, humidity, and soil water content plays an important role in growth, yield and quality of the plant. Effects due to changes in VPD are becoming increasingly more pronounced in coffee plants and are likely to lead to reductions in crop yield and quality. This article relates the increasing magnitude of VPD on coffee plants, their physiological effects, ecological impacts, and possible mitigations for the coffee industry.
The Physiology of Coffee Plants Under Increasing VPD
Water uptake and water loss through transpiration are in a balance, as with all vegetation. Increasing VPD would put such a balance under increasing pressure, especially since water compartments from the atmosphere increase the differences in water vapor pressure between the inside and outside of the plant, thereby accelerating transpiration. Increasing demand for water will force the stomatal conductance for that particular plant, which is the rate of vapor exit from the leaf, to decrease, thus conserving water. Reduced stomatal conductance would eventually lead to reduced photosynthetic rates since closure of stomata would also limit carbon dioxide uptake.
Prolonged high VPD can cause several adverse consequences in coffee plants:
Reducing Photosynthesis and Growth: The closing of stomata due to the reduction of transpiration has a downside-being associated with the carbon dioxide assimilating capacity of the plant. Thus, photosynthetic capacity is reduced, stunted growth occurs, and energy production by the plant is compromised.
Hydraulic Stress and Water Deficits: Coffee plants are very sensitive to dehydration as a result of shallow rooting systems and high demand for water. High VPD lowers turgor pressure of the plant causing wilting and possibly plant death when the deficiency gets very pronounced
Increase in Mortality of Plants: High VPD puts an additional susceptibility on coffee trees, but much more to older taller trees, to hydraulic failure. The possibility of dehydration and reduced carbon assimilation is greatly increased, leading to tree mortality in the end.
Increasing VPD's Ecological and Agricultural Impacts on Coffee
In the context of coffee production, whether at the community or ecosystem level, increased global temperature effects are the main factors influencing increased VPD trends. Coffee cultivation occurs in the tropics and sub-tropics, where temperature and humidity are essential factors for optimal growth, because increased VPD in coffee-growing regions will have an effect on alterations of local climate conditions, which would then lead to lower productivity and changes in suitable growing areas.
Shifts in Suitable Growing Areas: Coffee plants require stable temperatures and humidity. All suitable areas formerly for coffee growing may no longer provide optimal conditions for coffee and will only create a new environment for growth as VPD rises. This leads coffee farmers to adapt by moving cultivation to higher altitudes or a different geographic region; this is not likely to be applicable because it is becoming less likely for many viable cultivation areas to become increasingly limited with the rise of global temperature.
Water Stress and Soil Drying: In parallel with increased VPD, higher levels of evapotranspiration (ET) occur off soil and plant surfaces, which accelerate soil drying. Coffee plants depend on relatively stable moisture in their growing substrate and because of this, water stress may result in adverse impacts on such plants. This is of notable concern in the places where irrigation infrastructures are deficient in their power to balance evapotranspiration loss.
Changes in Quality and Quantity of Coffee Beans: Probably no other ingredient more directly affects the quality of coffee than the environment in which it is grown. High VPDs stress plants and cause them to be unable to produce uniform and high-quality beans, thus further adding to decreased quality at the time of harvest. Furthermore, reduced photosynthesis and water stress conditions give rise to low yields, thereby presenting other setbacks for farmers.
Mitigation Strategies for Coffee Producers
Strategies to be adopted by coffee producers in light of the rapidly increasing threat of rising atmospheric evaporative demand (VPD) among adaptive management strategies are known to be effective in making the necessary improvements that increase resilience to growing VPD:
1. Improved Irrigation Systems: Growing concern over water stress is driving the efficient application of irrigation technology such as drip irrigating, which guarantees consistent moisture to coffee plants. This is important in increasingly arid areas due to rising VPD.
2. Shade Management and Agroforestry: Increasing the shade around the coffee plant decreases direct sun exposure and thus serves to control the temperature and humidity around the plant so that the negative effects of high VPD are mitigated. Planting coffee in agroforestry systems with trees that provide shade and moisture retention is one good way to buffer against extreme environmental conditions.
3.Breeding for VPD-Resilient Varieties: Research into developing coffee varieties that have, for instance, deeper root systems or enhanced drought tolerance could actually prove to be one crucial resource strategy for the future. Farmers can, through selection or breeding, find coffee plants endowed with attributes that withstand the increasing VPD and thus secure more stable yields for their harvest.
4.Water Conservation Practices: Maintenance of optimal growing conditions for coffee under limited water resources can be ensured through promotion of water conservation practices such as mulching and management of soil moisture. Thus, such practices hold the potential to reduce soil-water evaporation and promote moisture conservation during periods when the VPD is at its peak.
Conclusion
Adverse increases in vapour pressure deficit (VPD) are one of the greatest threats to coffee production exposed to a changing climate. These increases in VPD precipitate increased physiological drought stress, which in turn brings about reduced growth, yield, and quality in coffee plants. This stresses coffee producers, especially in tropical areas, to prepare for changes through proper water management, adoption of agroforestry practices, and improvement of VPD tolerant coffee varieties. Addressing the VPD effect on coffee production would be critical in making the coffee industry survive regarding the livelihoods of millions of smallholder farmers who rely on coffee production as their source of income. Efficient climate adaptation strategies will be required for continued thriving in the coffee world.
Authored by
Digital Agronomy Team @ NeuBiom Labs
Akhila Unni
Prem Sidharth R
References
T.A. Mansfield, et al. “Stomata and Plant Water Relations: Does Air Pollution Create Problems?” Environmental Pollution, Elsevier, 4 Nov. 1998,.
Ainsworth, E.A. & Rogers, A. (2007) The response of photosynthesis and stomatal conductance to rising [CO2]: mechanisms and environmental interactions. Plant, Cell & Environment, 30, 258–270.
Kimberly A. Novick, et al. (2024) The impacts of rising vapour pressure deficit in natural and managed ecosystems. Plant, Cell & Environment - Wiley Online Library
Atkin, O.K. & Tjoelker, M.G. (2003) Thermal acclimation and the dynamic response of plant respiration to temperature. Trends in Plant Science, 8, 343–351.
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