Millions of people drink tea because of its health benefits, including its cancer-fighting compounds. Aside from water, tea is the world’s most popular beverage. Now some researchers are collecting early evidence that, as a result of climate change, major tea-cultivating regions in China may produce lower quality and less healthy tea in the future.
A team of researchers in embarking on a major study of three of China’s largest tea-growing provinces to look at this question, but early work and results suggests that this phenomenon is already playing out.
In China, there are several harvests a year, some during the monsoon season and others during the dry season. The wet harvests produce a lower-quality tea that usually commands a lower price for farmers, according to Selena Ahmed, a food systems researcher at Montana State University who has already collected preliminary data in southwestern China's Yunnan Province. The problem is that as the rainy seasons get longer and more severe they account for a larger percentage of each annual harvest.
To capture variability in the climate, Ahmed and a large interdisciplinary team will be measuring the chemical changes in the tea leaves grown in small-holding farms in three provinces over the next five years, helped by a recent $900,000 National Science Foundation grant. They’ll also be surveying whether Western consumers can perceive differences in taste among different quality products, interviewing farmers about their own perceptions and experiences, and modeling potential changes in prices that might affect the farmers themselves.
"The goal is to have this model where if we can say with X and Y changes happen, this is what’s going to happen to the tea," says Tufts University chemical ecologist Colin Orians, another researcher working on the project. (The rest of the interdisciplinary team includes University of Florida cultural anthropologist Rick Stepp and climate scientist and geographer Corene Matyas; and Tufts University agricultural economist Sean Cash, analytical chemist Albert Robbat, and crop and soil scientist Tim Griffin).
The early findings are concerning. They show, says Ahmed, that major health compounds that account for the desirable bitter and sweet taste of tea and for some of its antioxidant properties are reduced in the tea leaves harvested around the monsoon time (meanwhile, some other chemicals that don’t account for health benefits are boosted). Another concerning issue is that tea harvested in the wet seasons requires more drying and more processing—which could also reduce their healthy compounds.
"Our preliminary data shows that during the monsoon harvest in the Yunan province, we saw that the growth of tea leaves as measured by their size and weight almost doubles," says Ahmed. "But the phytochemicals that we measured which include the major antioxidants actually decreases by about half."
China is the world’s biggest tea producer, but farmers in other major regions including India are reporting changes in the taste of the tea they produce. This is worrisome for these region’s agricultural economies, since tea is one of the few crops for which quality has a big effect on price.
The researchers don’t know what will happen exactly as global warming affects the planet. Their goal is to understand all contingencies and possibly eventually apply their models to other kinds of crops. "One thing that was clear was across all of our interviews was that the tea plant and tea leaves and the final tea product was very much impacted by climate variability," says Ahmed.