Assessing the impacts of climate change on climate/land suitability for tea crop [Camellia sinensis (L) O. Kuntze] and the quality of young tea leaves in Sri Lanka

The impacts of climate change on tea production systems may be very variable, at both the national and global levels. In particular, Sri Lanka is considered vulnerable to climate fluctuations due to a variety of geographic, socioeconomic, and political factors. The predicted effects of climate change could have serious and irreversible consequences for tea production, quality, and habitats. Therefore, the consequences of climate change on Sri Lanka's tea industry should be extensively researched to determine its impact on production and quality, which in turn related to export revenues and employment for rural populations. However, information is exiguous on how climate change could affect climate/land suitability and tea quality under rainfed conditions in Sri Lanka. To narrow this gap, this study aimed at evaluating the effects of climate change on climate/land suitability for tea and its quality using a case study of Sri Lanka, a well-known high-quality black tea producer, as a classic example of a susceptible region. The study used species distribution techniques, geographic information system (GIS), remote sensing (RS)–based applications, and chemical analysis of tea leaves. The systematic review suggested that the impacts of the current and future climate on tea production systems outweigh the beneficial impacts, having multidimensional and multifaceted consequences. Tea yield increases when CO2 levels rise, but this positive effect could be hindered by rising temperatures. Further, tea yield would be negatively impacted by drought, uneven rainfall, and extreme weather events. For tea quality attributes, climate change can serve as both a boon and a bane, leaving questions and giving research priority to quantifying the thresholds of biochemicals to define tea quality, according to customer satisfaction. Climate change affects tea habitats by causing losses, gains, and shifts in climate suitability. Further review suggested the scarcity of appropriate method to model impacts of future climate changes on tea quality and for determining climate suitability for tea. It also highlighted the importance of implementation of adaptive and mitigation measures in tea production to alleviate the undesirable impacts of climate change. At regional scale climate modelling for Sri Lanka's tea sector, indicated that precipitation seasonality, annual mean temperature and annual precipitation are the three most important bioclimatic variables of tea habitat distribution in Sri Lanka. Land suitability classes for tea cultivation comprised of low suitability (42.1%), unsuitable (28.5%), moderate (12.4%), highly suitable (13.9%), and very highly suitable (2.5%). There is a chance of decrease in optimal and medium suitability areas in low-elevation regions in the future, with overall decline assessed to be between 8-17% for all suitability areas. This indicating that climate change will have a negative effect on the habitat suitability of tea in Sri Lanka by 2050 and 2070. Further, the refinement in land suitability classification through inclusion of other climatic and environmental variables (solar radiation, temperature, rainfall, topographic and soil) in climate model made two suggestions namely (1) there is a noticeable difference between tea- and non-tea-growing areas in terms of all above factors" (2) under future climate change scenario, tea-growing regions in Sri Lanka could expand to a range of locales, if some key variables are carefully managed. For tea quality assessment, model showed a significant interaction effect of weather conditions, cultivar, and geographical location over the concentrations of major tea quality biochemicals (total polyphenol content (TPC), free sugar, protein, and theanine) in tea leaves. The bioclimatic variables present seasonality (monthly range in temperature and precipitation), monthly trends (mean monthly temperature, monthly total precipitation), and extreme environmental variables (temperature of the coldest and warmest month, and precipitation of the wettest and driest months). They particularly caused changes in the four tested biochemicals of tea. The thresholds of all tested biochemicals are likely to increase with future climate change as temperatures and rainfall intensities are likely to increase. The distribution class with "very high" concentrations of TPC and theanine is expected to increase by 10% and 14%, respectively, in the future, while protein and free sugar classes are expected to decrease by 14% and 12%, respectively. For tea quality assessment, model showed a significant interaction effect of weather conditions, cultivar, and geographical location over the concentrations of major tea quality biochemicals (total polyphenol content (TPC), free sugar, protein, and theanine) in tea leaves. The bioclimatic variables present seasonality (monthly range in temperature and precipitation), monthly trends (mean monthly temperature, monthly total precipitation), and extreme environmental variables (temperature of the coldest and warmest month, and precipitation of the wettest and driest months). They particularly caused changes in the four tested biochemicals of tea. The thresholds of all tested biochemicals are likely to increase with future climate change as temperatures and rainfall intensities are likely to increase. The distribution class with "very high" concentrations of TPC and theanine is expected to increase by 10% and 14%, respectively, in the future, while protein and free sugar classes are expected to decrease by 14% and 12%, respectively