Peatlands cover only 3% of the Earth”s land area yet store more than 30% of the world”s soil carbon by preserving organic matter for thousands of years. However, a new study published on October 23 in Science raises concerns about the impact of extreme droughts on these critical carbon reservoirs, suggesting that such events could significantly increase carbon emissions in a warming climate.
The research indicates that under simulated future climate conditions—characterized by higher temperatures and elevated carbon dioxide levels—extreme drought can lead to a nearly threefold increase in carbon release from peatlands. This could transform these ecosystems from valuable carbon sinks into carbon sources, possibly erasing decades of carbon storage within a matter of months.
Conducted at an experimental site in northern Minnesota, the study involved manipulating temperature and carbon dioxide levels inside controlled test chambers. “As temperatures rise, the frequency and severity of droughts increase, making peatlands even more vulnerable,” stated Yiqi Luo, the senior author of the study and the Liberty Hyde Bailey Professor in the School of Integrative Plant Science”s Soil and Crop Sciences Section, within the College of Agriculture and Life Sciences.
Luo emphasized the importance of the findings, noting that extreme drought events have the potential to eliminate centuries of accumulated carbon. This research is particularly timely, given that the Intergovernmental Panel on Climate Change predicts that the likelihood of extreme drought will increase significantly in the near future.
While it has been known that drought conditions reduce ecosystem productivity and heighten carbon emissions in peatlands, this study is pioneering in its focus on how such losses will be exacerbated by climate change. The researchers found that the water table in peatlands takes longer to recover during droughts when temperatures and carbon dioxide levels are elevated, resulting in more carbon being released into the atmosphere.
Interestingly, the study revealed that while elevated carbon dioxide can boost productivity in upland ecosystems, it has the opposite effect in peatlands during drought. “Our results indicate that increased carbon dioxide levels, combined with higher temperatures, lead to a dramatic rise in carbon emissions,” Luo remarked.
The team, including first author and postdoctoral researcher Quan Quan, analyzed data from a field experiment in a natural boreal spruce bog. Through their research, they discovered that higher levels of carbon dioxide within the peat bog increased both the substrate and dissolved carbon content. When this dissolved carbon encounters oxygen during drought conditions, it results in a greater release of carbon dioxide.
Since 2015, Luo has been part of a collaborative effort involving 250 researchers at the experimental site, working to integrate collected data with models to better understand peatland responses to environmental changes. Other contributors to this study include postdoctoral researchers Jian Zhou and Ning Wei, along with senior research associate Lifen Jiang, and researchers from various esteemed institutions.
The research received support from several organizations, including the National Science Foundation, the U.S. Department of Agriculture, and the U.S. Department of Energy”s Office of Biological and Environmental Research.
