A recent study published in Nature Climate Change reveals that savannas and grasslands in drier climates have been storing more heat-trapping carbon than previously understood, making a significant contribution to mitigating climate change, the University of Michigan (U-M) said in a statement Monday.
The research involved a reanalysis of data from 53 long-term fire-manipulation experiments worldwide and on-site sampling at six of those locations, with contributions from researchers across the globe, including the University of Michigan.
Savannas represent tropical or subtropical grasslands found in regions like eastern Africa, northern South America, and elsewhere, characterized by the presence of scattered trees and resilient undergrowth that can withstand periods of drought.
The study indicates that within savanna and grassland regions, drier ecosystems are more susceptible to changes in wildfire frequency compared to their more humid counterparts.
Dryland savannas have experienced a 23% increase in stored topsoil carbon over the last two decades due to a reduction in wildfire frequency, which was not anticipated by existing ecosystem models.
This suggests that the climate-buffering role of these regions has been underestimated, according to forest ecologist and study second author Peter Reich, professor and director of the Institute for Global Change Biology at the U-M School for Environment and Sustainability.
Dryland savannas and grasslands around the world have accumulated approximately 640 million metric tons of carbon in their soils during this period.
However, it is worth noting that while this is a substantial amount, it will not single-handedly offset human-caused carbon emissions.
Instead, these regions, when considered collectively with other biomes, can contribute significantly to slowing climate change, study lead author Adam Pellegrini, currently an exchange professor at the U-M Institute for Global Change Biology, explained.
Importantly, some savanna and grassland regions are working on soil carbon credit projects, emphasizing the relevance of understanding their capacity for carbon sequestration.
While this study sheds light on the potential of these ecosystems to play a role in climate change mitigation, the researchers caution that the future of these regions in terms of carbon storage remains uncertain and contingent on various factors.
The study was funded by various organizations, including the U.S. Department of Agriculture (USDA), UK Research and Innovation (UKRI), the Gordon and Betty Moore Foundation, and the U.S. Department of Energy (DOE), highlighting the global interest in understanding the carbon dynamics of savannas and grasslands in combating climate change.