Condition changes of the Bagna Izbickie peatland Nature Reserve in Poland using RSEI indicator, within 1985 – 2020

The study examined ecological changes occurring in a Baltic raised bog in northern Poland. The analysis covered the period from 1985 to 2020, using 5-year intervals. Landsat TM C2 L2 imagery (1985–2010) and Landsat OLI C2 L2 imagery (2015–2020), obtained from USGS.gov, were used. For the analyses, images with the lowest possible cloud cover from June were selected. Based on these data, indices including NDVI, NDBSI, LST, and WET were calculated, followed by a principal component analysis (PCA) to derive the composite Remote Sensing Ecological Index (RSEI). To analyze RSEI values across individual years and within different land cover classes, supervised classification of the scenes was carried out using the maximum likelihood method. RSEI data were then compared with climatic variables (precipitation, reference evapotranspiration, actual evapotranspiration, runoff, and climatic water deficit). Climate data were obtained from TerraClimate via climateengine.org. The results revealed clear differentiation among land cover classes—forest, grassland, and bog. An upward trend in RSEI values was observed across all land cover classes during the study period, although the total area of peatland declined, largely in favor of forest expansion.