Peatlands, which occupy only 3% of the Earth”s land surface, are significant carbon reservoirs, storing over 30% of the world”s soil carbon. However, a recent study published on October 23 in Science warns that these ecosystems are at risk of releasing vast amounts of carbon due to extreme droughts exacerbated by climate change.
The research indicates that under future climate conditions characterized by increased temperatures and higher carbon dioxide levels, extreme drought could lead to nearly threefold increases in carbon emissions from peatlands. This transformation poses a serious threat, as it could erase between 90 and 250 years of carbon storage within just a few months.
Conducted in northern Minnesota, the study utilized controlled test chambers to simulate environmental conditions. “As temperatures increase, drought events become more frequent and severe, making peatlands more vulnerable than before,” stated Yiqi Luo, the lead author and a professor at the School of Integrative Plant Science. “We add new evidence to show that with peatlands, the stakes are high.” He emphasized that the findings illustrate the potential for extreme droughts to eliminate centuries” worth of accumulated carbon.
While the impact of drought on ecosystem productivity and carbon release in peatlands has been previously established, this study is groundbreaking in its examination of how warming and elevated carbon dioxide levels intensify carbon loss. The Intergovernmental Panel on Climate Change has projected that the likelihood of extreme drought will increase by 1.7 to 7.2 times in the near future. Luo highlighted that these results serve as a critical warning about the severe consequences of global warming, urging attention to peatlands despite their limited geographic footprint.
Peatlands are a crucial carbon reservoir compared to other ecosystems, according to Luo. “We need to find a way to mitigate climate change and bend the warming curve,” he asserted.
The research team, including postdoctoral researcher Quan Quan, analyzed data from a field experiment in a natural boreal spruce bog in Minnesota, using ten 20-meter-wide yurt-like chambers. The study focused on the carbon loss from peatlands during a severe drought event in July and August of 2021, testing ten future climate scenarios.
The study”s findings revealed that during drought, the lowered water table took longer to recover under elevated temperatures and increased carbon dioxide levels, resulting in even greater carbon emissions. Luo noted that while he anticipated warm temperatures would contribute to carbon loss, the extent to which elevated carbon dioxide also exacerbated this loss was unexpected.
Interestingly, in upland areas, increased carbon dioxide can enhance photosynthesis and improve water efficiency in plants, mitigating some effects of drought. However, in peatlands, the situation is different. The research indicated that elevated carbon dioxide alone could boost ecosystem productivity, but when combined with a temperature rise of 9 degrees Celsius, there was a dramatic increase in carbon emissions during the 2021 drought.
Quan”s analysis revealed that the rise in carbon dioxide levels led to higher amounts of substrate and dissolved carbon in the bog. Under drought conditions, exposure of dissolved carbon to oxygen facilitated greater carbon dioxide release into the atmosphere.
Since 2015, Luo has collaborated with a team of 250 researchers at the experimental site, focusing on integrating collected data with models to understand how peatlands respond to environmental shifts. The study received support from several organizations, including the National Science Foundation and the U.S. Department of Agriculture.
