Climate change threatens tea crops

Everyone knows that climate change threatens coastlines and wildlife. But its effects won’t be limited to destroying property and altering the natural world; it will also affect the quality of experiences and products we now take for granted -- such as the simple ritual of sipping a cup of tea.

A group of scientists including a Tufts University chemical ecologist are exploring the effects that climate change will have on tea crops in China, supported by a four-year, $931,000 grant from the National Science Foundation. The scientific scrutiny of tea highlights the way in which climate change’s effects are not simple; it may alter desirable characteristics of products and cause economic ripples for producers and consumers.

Tea may seem like a narrow topic to study, but it is a big business. In the United States, people spend $2 billion on tea at supermarkets, according to the Tea Association of the USA. The researchers hope to specifically understand better what chemical changes are occurring in tea leaves in response to different environmental conditions. They want to trace how these changes affect the quality of the product and farmers’ ability to sell the crop to buyers. Those lessons may be valuable for a wide array of business owners, such as wine producers and cherry farmers, but also ski resort operators.

Colin Orians, a professor of biology at Tufts, sees tea as an ideal way to study fundamental questions about plant biology, including how external conditions influence plants’ allocation of resources toward making defensive chemicals that protect them against getting eaten. He studies how plants divide up their energy between functions such as growth, storage, and defense and first got interested in tea when Selena Ahmed, a postdoctoral researcher who has since moved to Montana State University, came to his laboratory.

I asked Orians to answer a few questions about the research by e-mail. His answers, edited for length, are below.

Q: How did you get involved in this research?

A: Most crops, consider lettuce, have been bred to grow fast, and thus it is not surprising that crops like lettuce do not provide us with some of the known health benefits, such as antioxidants, that ancestral crops might have contained. This is exacerbated by the fact that we grow crops under the most favorable environmental conditions that cause a plant to prioritize growth over defense. Tea is different! It has always been valued for its chemistry, its medicinal properties, and I was immediately intrigued by the system. How will climate change alter its chemistry? Can we use plant defense theory to understand and predict future changes in chemistry? How will these changes affect consumers and ultimately farmer livelihoods?

Q: Is this more than an academic interest -- are you a tea connoisseur?

A: I have come to appreciate good tea. I love drinking tea that is so rich in flavor that I have no desire to add anything to it. I really enjoy teas from southern China.

Q: When did changes in tea quality begin to be noticed?

A: It is known that the chemistry of tea shifts in response to the onset of the monsoons. What our preliminary work was able to show was that farmers perceive these changes, that the changes happen within days of the onset of the monsoon, that buyers pay substantially more for the pre-monsoon spring tea, and that the monsoons are arriving earlier in this area of China (Yunnan). Importantly we showed that within 5 days of the arrival of the monsoons, what farmers harvest has twice the biomass (plants are growing faster) but lower concentrations of some key phenolics known to be important in tea. We are in the process of more thoroughly characterizing the change in chemistry and taste, and plan to compare teas from different regions as part of the study.

Q: Would the changes be noticeable to people who aren’t very picky (i.e. drink tea out of bags)?

A: I believe many could notice the changes. We are putting together a trained sensory panel and our preliminary analysis of teas showed that everyone was easily able to distinguish between tea picked in the spring and that picked after the monsoons arrived. Of course bagged tea is often blended so we would expect tea companies to try new blends to limit any changes perceived by the consumers.

Q: How widespread are these issues among tea-producing regions of the world?

A: Globally, climatic conditions are becoming more and more variable and we are working with a climatologist to explore how conditions are changing in some of the key tea producing regions. I might expect the change to be highest in regions influenced by monsoons since increases in precipitation have such a large effect on tea. Yet, because farmers harvest buds and young expanding leaves, the chemistry of the tea depends on the current conditions in which the plants are growing. Any climatic shifts could have an impact on tea quality.

Q: Are tea leaves more sensitive to climate change than other crops? What about coffee?

A: This is a great question but not one that can be answered. There is concern about the effects of climate on grape and coffee production, for example, but there are no comparative studies. Strong scientific arguments could be made for the greater sensitivity of each crop.

Q: Typically, when people think about the effect climate change will have on agriculture, they worry about crops failing. Do you expect these changes are already occurring in other agricultural products?

A: Yes, we tend to focus so much on yield when thinking about climate change but this emphasis loses sight of the importance of quality. Is climate changing the quality of spinach, kale or blueberries? I think we all could come up with a list of a dozen food and beverage items that we regularly consume because they are good for us. I want to know how those benefits are, or might be, changing.