From subsidence to carbon emission: a conceptual and remote sensing-based framework for quantifying peatland carbon loss

Peatland degradation fundamentally shifts these ecosystems from carbon (C) sinks to major C sources; yet large-scale emission estimates remain highly uncertain due to the challenges of conducting field measurements. Carbon loss reduces the volume of peat, causing peat subsidence; therefore, a direct relationship exists between C emissions and surface displacement. The primary aim of this study is to establish a fully remote-sensing-based framework that links peat subsidence (detectable via satellite observations) to carbon emissions without requiring ground-based sampling. To operationalize this, three critical parameters are required: bulk density (BD), soil organic carbon (SOC), and the oxidation component of subsidence (the fraction of total subsidence attributable to oxidative peat loss). We developed a methodology to derive these parameters by integrating Sentinel-1 InSAR subsidence data with spatially distributed peatland typologies from global archives and empirical relationships between groundwater levels, subsidence, and oxidation. Applying this framework across the Biebrza Valley peatlands in northeastern Poland, we observed a mean annual subsidence rate of 1.4 cm.yr^-1. The derived parameters averaged ~35% for the oxidation component, 120 kg.m^-3 for BD, and 389 g-C.kg^-1 for SOC. Validation against field surveys confirmed high accuracy, with normalized differences for peat properties remaining below 0.14. The framework yielded a mean emission estimate of 7.49 ± 3.6 tons.CO_2-eq.ha^-1.yr^-1. Notably, this framework aligns more closely with field-validated parameters than the “common approach” (using constant BD and SOC values), which was found to overestimate emissions at 14.49 tons.CO_2-eq.ha^-1.yr^-1. This framework offers a scalable and cost-effective solution for assessing carbon emissions from peatlands, particularly in areas where field access is limited. Its application across diverse peatland types could support continental-scale emission estimations and peat carbon inventories for climate mitigation, as well as evaluating restoration planning.