Potential overestimation of carbon dioxide emissions from croplands on organic soils in cool temperate and boreal regions based on a case study from Norway

Abstract Peatlands drained for agriculture and other uses release substantial carbon dioxide. Many countries estimate these emissions using the 2014 IPCC Tier 1 emission factors. Here we calibrated an ecosystem model with data from two cultivated peatland sites in Norway and simulate carbon dioxide emissions at 50 sites nationwide for 2001–2022. Model results showed that carbon dioxide emissions were strongly controlled by water table depth and aligned well with observations from other European peatlands of similar climate zones. Crucially, the Tier 1 emission factor matched our simulations only under very deep water tables (< –0.7 m), but overestimated emissions by 31–88% when water levels ranged from –0.7 m to –0.3 m. This indicates that Tier 1 methods may overstate emissions from cultivated peatlands in cool temperate and boreal regions, inflating estimates of mitigation potential. Tier 2 or 3 approaches can reduce uncertainty but require more field data.