A remote-sensing-based framework to detect the rate of peat subsidence and associated CO2 emissions: A case study of the Biebrza Valley, Poland

Peatlands are vital ecosystems that provide essential ecological services, especially in carbon storage. Nevertheless, the decomposition of surface peat and subsequent carbon emission threaten to accelerate the pace of climate change. This study presents a framework designed to facilitate the estimation of peat subsidence and relevant CO₂ emissions through the exclusive utilization of remote sensing techniques. In this study, the peatland subsidence in the Biebrza Valley, Poland, was estimated by using the Alaska Satellite Facility Interferometry Synthetic Aperture Radar on-demand cloud computing via a Small Baseline Set technique and seasonal-annual search approach covering the period from April 2015-April 2022. The amount of subsidence and associated carbon emission rates can be estimated by analyzing InSAR data from a selected period. The results reveal an annual peatland subsidence rate of 2.1 cm, verified through field surveys. An R² value of 0.91, and an RMSE value of 0.23 cm indicate the reliability of this approach in estimating the subsidence. These findings unveil a troubling trend in the Biebrza National Park, with almost 88 MCM of its peatlands lost during the seven years from 2015-2022. Two different approaches were employed to estimate CO₂ emissions associated with subsidence, each with three scenarios. Therefore, the estimation of annual peatland carbon dioxide loss, ranging from 3.24 to 5.36 tons per hectare through the remote sensing-based approach, compared to the broader range of 20.3 to 33.9 tons/ha/yr obtained from the common approach. It means that, based on the first approach, in the most optimistic scenario, the park is associated with a minimum of 1.35 million tons of carbon dioxide emissions during this period, potentially reaching as high as 2.26 million tons in the worst-case scenario. In contrast, the common approach indicates a wider range of emissions, ranging from 8.5 to 14.2 million tons over these years.