Rising Temperatures May Reduce Carbon Storage in Wetlands

A new global study suggests that rising temperatures may reduce the amount of carbon stored in wetlands and bogs. This conclusion was reached by an international team of 110 scientists who studied the decomposition rates of green and rooibos tea in 180 wetlands across 28 countries to evaluate the carbon storage capacity of bogs (Figure 1).

Figure 1. Experimental sites included in the study.

The study, published in the prestigious journal Environmental Science and Technology, included contributions from scientists Ilze Ozola, Ieva Grudzinska-Elsberga, and Normunds Stivrins from the Lake and Peatland Research Centre. In Latvian peatlands, two types of tea bags were buried at a depth of 15 cm, and the changes in organic matter volume were measured over a three-year period. The results were then used to calculate carbon retention trends (Figure 2), which complemented the global data set from other wetlands and peatlands.

Figure 2. Tea bag experiment in Kaigu peatland (fen peat conditions).

Green tea bags contain organic material that decomposes quickly, whereas rooibos tea decomposes more slowly. The use of tea bags provides a simple and standardized method to determine how climate, habitat, and soil type influence the rate of carbon decomposition in wetlands. The differences between these two types of tea allowed researchers to gain a more comprehensive understanding of the carbon storage capacity of wetlands.

Although the use of tea bags in science is a well-tested and validated method for determining carbon release from soil into the atmosphere, this is the first time that tea bags have been used for such a large-scale and long-term study in wetlands.

The results indicate that, overall, higher temperatures accelerated the decomposition of organic matter, reducing carbon retention in soil and peat. It was found that freshwater wetlands and tidal marshes retained the most tea mass, indicating a greater potential for carbon storage and retention in these ecosystems. The data from Kaigu peatland suggest that, while newly accumulated organic material in fen peat may be sensitive to rising temperatures, this ecosystem has a higher carbon storage potential compared to other types of wetlands.

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