How is climate affecting tea quality in China?

GUEST BLOG: Q&A with an ethno-botanist on the SOCIO-ECOLOGICAL ASPECTS OF TEA QUALITY

Answering the questions: Dr Selena Ahmed
Assistant Professor of Sustainable Food Systems
Food and Health Lab, Montana State University

Is climate change changing the taste of tea? Can producers and consumers perceive such changes? What are implications for farmer livelihoods and benefits we derive from tea as consumers? In this blog we find out more from a team of researchers working in China.

What’s so special about tea in China?
Tea is cultivated, processed and prepared in diverse ways in China. This diversity makes tea in China very special to me. China is regarded the motherland and centre of genetic diversity of tea with over 1,500 cultivars of the tea plant. It also grows in gorgeous systems from forests to shade-grown gardens to mixed plot fields.  I recently returned from a great field season in Yunnan Province of SW China where I sampled tea and interviewed farmers on climate effects on tea quality. As part of this fieldwork, I had the opportunity to eat fresh tea leaves harvested right off the plant – this is one of my favourite edibles. I also drank what seemed like infinite cups of spring tea that the tea farmers I was staying with harvested the same very week. This tea is characterised as full-bodied, complex, and bitter-sweet. What makes tea from these gardens in Yunnan discernible is the lingering sweet after taste that sticks like honey to the back of the throat in a sensation known in Chinese as gaan.

When is the best time to taste tea?
Anytime! With that said, spring tea harvest has come to be my favourite harvest. The spring harvest is also the most desirable harvest for tea entrepreneurs who make the trek out to the tea mountains from major cities of China in search of the young spring buds. The spring is when the buds and leaves are awakening from winter dormancy and also when the plants grow in relatively dry conditions that are suitable for tea quality. This spring, tea farmers in Yunnan Province shared that the tea harvest started a little earlier than in the past, while being a little later than in previous years. Tea farmers attribute this to changing climate factors as well as to land use change that impacts the local micro-climate.

What attributes determine the quality of tea?
Tea quality is determined by sensory characteristics and secondary metabolites that impart health benefits for human consumers. Secondary metabolites are compounds that are produced by plants for defense. Unlike animals that can move away from predators or uncomfortable environmental stress, plants are rooted and have evolved defense compounds to protect themselves from a range of environmental stress. Thus, tea quality is intricately linked to environmental, agrarian, and cultural factors. For example, the quality of tea harvested from an organic system is different than that harvested from a conventional system. Or that harvested from high altitudes varies from that at lower altitudes on the same mountain. I have been working in the motherland of the tea plant, SW China, since 2006 to examine how changing environmental and cultural factors impact tea quality. Here, indigenous communities cultivate tea in diverse systems including shade-grown agro-forests and mixed cropping. Leaves harvested from these systems differ in their quality.

So why is your research important?
Our research on climate effects on tea quality is important for several reasons. First, tea is the most consumed beverage in the world after water and thus any changes in tea quality from climate change would have consequences for a notable percentage of the world’s population. 
Second, in many instances, tea is produced by smallholder farmers as a primary source of income. Changes in income derived from tea that are driven by climatic shifts would thus impact these smallholder farmers. Farmers have continuously shared their perspectives regarding how climate factors and seasonality are major drivers of tea quality. Third, our project fills an important research need by focusing on climate effects on  crop quality. While it is well understood that more frequent and intense climate events in many areas are impacting crop yields, the impact on crop quality is less acknowledged. Knowledge on tea quality is critical for food systems that benefit both farmers and consumers through high-quality products. The framework developed and tested by our research may be applied to other speciality crops such as fruits, vegetables, wine, coffee, tea, maple syrup, and chocolate – all these products have unique secondary metabolite profiles that are notably impacted by the environment and management practices.

How do you measure the effect of climate on tea quality?
We are examining climate effects on tea quality through a multi-pronged approach involving field sampling of tea, controlled field and greenhouse experiments, laboratory analyses of biochemicals, sensory evaluation, consumer taste experiments, farmer surveys, and climate modelling. While data exists to create simulations on how tea yields in China may vary with forecasted climate models, there is a lack of information on how tea quality will vary. Consequently, we are collecting tea quality data through sampling of tea during different seasons that have distinct temperature and precipitation characteristics including the spring, summer and autumn season. We started this sampling in 2012 and plan to continue until 2016. In addition to our field site in Yunnan, we are also sampling in Zhejian and Fujian Provinces. At each location, we have a high elevation and a low elevation site. After the samples are harvested, they are used for various sensory experiments with tea farmers and connoisseurs, tea panels, and general western consumers. A portion of the samples are also sent to the lab where they are analysed for key aroma compounds that determine tea quality.

What have your results found so far?
Preliminary findings from our work have found that tea functional quality significantly varies with extreme weather events, which are becoming more frequent with climate change. Specifically, compared to an extreme spring drought, tea leaves grown during the monsoon at our study site in SW China were up to 50% higher in terms of growth parameters while concentrations of major compounds that determine tea functional quality were up to 50% lower. This suggests that changes in precipitation may have a dilution effect on tea quality or cause drought or water stress.

What does this mean for farmers?
A decrease in tea quality is associated with a decrease in tea prices and income derived from tea sales; which substantially impacts upon farmers’ livelihoods. Our findings validate farmer perceptions that precipitation impacts tea quality. Extrapolating findings from this study to long-term climate change suggests variability for farmers and the need to tap into farmers’ knowledge of management practices to mitigate climate risks in their agro-ecosystems for the sustainability of tea production.

What’s next?
We will continue sampling extreme seasonality variability for the next two years and we will carry out controlled experiments with tea plants in conditions that manipulative climate scenarios in tea-producing areas. This work will be coupled with interviews with farmers and consumers. Our studies with farmers involve determining behavioural responses of consumers to climate-induced changes in tea quality and yields and their implications on tea markets regionally and globally. At the farm-level, we are documenting how livelihood changes and tea farmer knowledge of climate effects on crop quality and yields feedback into the way farmers adapt their management and tea processing to adapt to climate conditions.

Can you predict whether the Chinese tea will taste different in the future?
Ultimately, we will input tea quality into a climate model to simulate future tea quality in different geographic areas on the basis of climate projections. We will also integrate findings from our lab analyses and interviews to use this evidence to develop management plans and policy suggestions for tea agro-ecosystems and processing, and ultimately facilitate societal action towards enhanced sustainability of food systems.

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In addition to tea, Selena has begun to explore how climate is impacting other speciality crops. She recently received funding with another interdisciplinary team to explore climate effects on maple syrup quality and socio-ecological responses.

Selena’s research is funded by the USA National Science Foundation’s Dynamics of Coupled Natural and Human Systems (CNH) Program. The interdisciplinary team of scientists examining how climate effects tea quality includes Colin Orians (chemical ecologist), Albert Robbat (chemist), Tim Griffin (soil scientist), Rick Stepp (cultural anthropologist), Sean Cash (agricultural economist), Corene Matyas (climate scientist), Wenyan Han (tea and soil scientist), and Selena Ahmed (food systems scientist). Each of the team contributes different perspectives and methodologies from their fields to address this interdisciplinary issue. If you have any questions on their research please direct them to selena.ahmed@montana.edu.

For more info on their research see www.teaclimate.org

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