To some scientists studying climate change, boreal peatlands are considered a potential ticking time bomb. With huge stores of carbon in peat, the fear is that rising global temperatures could cause the release of massive amounts of CO2 from the peatlands into the atmosphere–essentially creating a greenhouse gas feedback loop.
A new study by researchers at the University of South Carolina and University of California Los Angeles challenges that notion, and demonstrates that the effect of temperature increases on peat storage could be minor.
The researchers used the biochemical composition of a peat core collected from the James Bay Lowland in Canada to assess the historical relationship between climate and the extent of peat decomposition.
The core is a record of peat accumulation over the last 7,500 years and contains two intervals (the Medieval Climate Anomaly and the Holocene Thermal Maximum) when temperatures were about 2 C warmer than normal, providing a natural analogue for modern warming.
However, peat formed during these warm intervals was not extensively decomposed compared to peat formed during cooler periods. Instead, the most extensive decomposition coincided with drier conditions and longer oxygen exposure time during peat formation.
This indicates oxygen exposure time was the primary control on peat decomposition, while temperature was of secondary importance.
This was supported by comparing the extent of decomposition along a climate transect in the West Siberian Lowland, Russia. Cores from the northern end of the transect, which experienced longer oxygen exposure times, were more decomposed than cores from the south, which formed under warmer temperatures.