The carbon sink potential of peatlands depends on the balance of carbon uptake by plants and microbial decomposition. The rates of both these processes will increase with warming but it remains unclear which will dominate the global peatland response. Here we examine the global relationship between peatland carbon accumulation rates during the last millennium and planetary-scale climate space. A positive relationship is found between carbon accumulation and cumulative photosynthetically active radiation during the growing season for mid- to high-latitude peatlands in both hemispheres. However, this relationship reverses at lower latitudes, suggesting that carbon accumulation is lower under the warmest climate regimes. Projections under Representative Concentration Pathway (RCP)2.6 and RCP8.5 scenarios indicate that the present-day global sink will increase slightly until around AD 2100 but decline thereafter. Peatlands will remain a carbon sink in the future, but their response to warming switches from a negative to a positive climate feedback (decreased carbon sink with warming) at the end of the twenty-first century.
The work presented in this article was funded by the Natural Environment Research Council (NERC standard grant number NE/I012915/1) to D.J.C., A.G.S., I.C.P., S.P. and P.F., supported by NERC Radiocarbon Allocation 1681.1012. The work and ideas in this article have also been supported by PAGES funding, as part of C-PEAT. CDJ was supported by the Joint UK DECC/Defra Met Office Hadley Centre Climate Programme (GA01101). This research is also a contribution to the AXA Chair Programme in Biosphere and Climate Impacts and the Imperial College initiative on Grand Challenges in Ecosystems and the Environment. This research was also supported by a grant from the National Science Centre, Poland 2015/17/B/ST10/01656. We wish to thank Dale Vitt, Jukka Alm, Ilka E. Bauer, Nicole Rausch, Veronique Beaulieu-Audy, Louis Tremblay, Steve Pratte, Alex Lamarre, David Anderson and Alex Ireland for contributing data to this compilation. We are also grateful to Steve Frolking for suggestions on different moisture indexes and to Alex Whittle and Fiona Dearden for their work in the Exeter laboratories.
- carbon cycle
- climate change
- tropical peat
- last millennium