Joshua Lee Ratcliffe, Haijun Peng, Jelmer Nijp, Matts B. Nilsson

Peatlands contain one of the largest stores of terrestrial carbon and exert a considerable influence on the global climate cycle. However, both the magnitude of the peatland carbon pool and the development of this pool through time are poorly constrained. In a recently published article, Nichols and Peteet combine basal radiocarbon dates from palaeoecological studies with previously published datasets of peatland initiation to produce a revised estimate of northern peatland initiation and carbon stocks. The authors conclude that the amount of carbon stored in Northern peatlands is two to three times higher, i.e. 1055 Gt C, than previous estimates. Nichols and Peteet argue this is due to peatlands initiating and expanding earlier than previously thought, as appears to be the case in the new dataset of peatland initiation they have compiled, of which dates from the palaeoecological literature (Neotoma database) form a large component. The approach used by Nichols and Peteet relies on two assumptions 1) That the lateral peatland coverage expands linearly with time and 2) that the oldest basal date in a region is representative of peat initiation in that region. These assumptions have been repeatedly called into question as has the suitability of the Neotoma dataset for basal date information without modern re-processing. We consider peat depth as a means to independently evaluate the 1055 GtC figure, concluding that this would require peatlands to be implausibly deep as compared to peat depth observations.