Need to calm down before bed? Try chamomile tea. Need to settle an upset stomach? Sip some ginger tea.
Do you need to measure how much carbon can be sequestered in an anaerobic wetland environment? We recommend Lipton green and rooibos tea in the bag.
“We’ve got these two types of tea, and by comparing them, we can get a better idea of the processes going on in these different ecosystems,” explained John Berges, a UWM professor of biological sciences.
Berges and his colleague, UWM Biology Professor Erica Young, were part of an international cohort of researchers working in various wetland ecosystems – freshwater, marine, flowing water, still water, etc. – to determine the extent to which each environment can store carbon and keep it from being released into the atmosphere as carbon dioxide. They did it with a novel testing method: Burying the same types of tea bags in all those wetlands worldwide and measuring how quickly they decayed. The research began in 2017, but the scientists’ work was finally published in November 2024 in the journal Environmental Science & Technology.
The paper concludes that the greatest factor contributing to the loss of carbon storage in wetlands is warmer temperatures.
“Many of us thought going in that the biggest (factor) would be the lack of oxygen in sediments. … If there’s no oxygen, (matter) can’t degrade quickly,” said Berges. “That’s not what we found. Across the ecosystems, the one factor that we found that was really influential was temperature.”
As climate change contributes to rising temperatures around the globe, that could mean that wetlands will release more carbon dioxide into the atmosphere, contributing to more climate change.
But how, exactly, does one use Lipton to measure carbon sequestration? Here’s the tea.
Tea has its benefits
Living organisms, including plants, are composed of carbon. When those organisms die and decompose, that carbon is released into the atmosphere as carbon dioxide. If matter can be kept from decomposing, that is what’s referred to as carbon sequestration. The more carbon sequestered and stored as matter, the less is recycled into the atmosphere.
When scientists have studied carbon sequestration in ecosystems on land, they’ve gathered fallen leaves in mesh bags, staked the bags in the woods, and weighed them periodically to see how much leaf mass was lost to decay and carbon recycling.
“We know how to do that in a forest. The question has always been, how do we do it in a wetland?” said Berges.
Enter the tea bags.
Tea leaves are plant matter, so they decay like tree leaves in nature. They come in standardized tea bags, so researchers know they use the same sample size. The tea bags are meant to be steeped in water, so the bags are sturdy enough to keep the samples together in a wetland.
The project’s principal investigator, Stacey Trevathan-Trackett at the Royal Melbourne Institute of Technology in Australia, agreed to name Lipton as a sponsor of the experiment if the company would supply researchers with tea bags for free. She gathered a team of scientists across 28 countries and shipped the tea bags to everyone so that they could bury them in wetlands around the world – including right here in Milwaukee.
A wetland environment
Berges and Young have always thought that Estabrook Park Pond in Shorewood, Wisconsin makes a wonderful classroom. It supports complex ecosystems, it’s close to UWM, and it’s shallow enough to send biology students out wading to collect water samples – or in this case, to bury tea bags.
Lauren Simmons said that’s as tricky as it sounds. Simmons is the Chair of Art History and Natural Science at the Milwaukee Institute of Art and Design, but in 2017, she was a UWM PhD student assisting Berges and Young with their research.
“Once you dig to the depth that you want, you put the bag in, and you hold it down as you’re trying to bring the muck back over it,” Simmons said. “We were as technical as we could be. The setup was very easy. The recovery part was the most difficult part.”
After the tea bags were buried, the researchers had to dig them back up at various intervals over two years, dry them, and weigh them to see how much tea had decomposed. There were some obstacles.
“We strategically placed items like rocks (to mark) where the tea bags are. But …. even though you put a rock there, the pond tends to kick up a lot of muck from people running in it, dogs running in it, animals in general,” Simmons said. “So, there was a lot of digging around in the muck trying to recover what we could. We did lose a few tea bags.”
In spite of that, they found interesting results.
Tea takeaways
“At Estabrook, we were one of the fastest degrading sites (tested in the experiment),” Berges said. After three months, for example, a green tea bag had lost 80% of its carbon and a rooibos tea bag had lost 40% (Rooibos is more resistant to degradation than green tea, said Young).
By comparison, most other wetlands lost about 50% of carbon from green tea and 30% from rooibos tea in the same timeframe.
Why does Estabrook Pond recycle carbon faster than other wetlands? There could be several factors: The acidity of the water, the presence of microbes, or the amount of other carbon available in the environment. The tea bags were buried under shallow water, Berges said, so perhaps the water temperature warmed above the tea bags and contributed to their degradation as well.
Overall, the results highlight the important, and often overlooked, part that wetlands play in carbon sequestration.
“They store an awful lot of carbon,” Berges said. “We think about the Great Lakes as a very precious resource, but in terms of the area of water here in the United States, they’re small compared to all of the land area that’s covered by these small ponds.”
“What happens to (plant matter) when it gets into these wetlands is really important for the global carbon balance,” added Young.
Researching wetlands and climate isn’t everyone’s cup of tea, but for these UWM biologists, it definitely is – in every sense of the phrase.
By Sarah Vickery, College of Letters & Science