Four decades of hydroclimate-driven change and ecological condition in a Baltic raised bog assessed with Landsat and RSEI.

Peatlands are key carbon stores but are highly vulnerable to hydroclimatic change and drainage legacies. We combined TerraClimate water-balance variables with Landsat Collection 2 surface reflectance imagery to quantify four decades (1984–2024) of land-cover change and ecological condition in the Bagna Izbickie Baltic raised bog (northern Poland). Land cover was mapped in Google Earth Engine using a Random Forest classifier into forest, bog and grassland classes, and ecological condition was assessed with the Remote Sensing Ecological Index integrating greenness, wetness, heat and dryness components. Hydroclimate showed progressive summer warming and an increasing atmospheric water demand, while precipitation remained strongly variable. The landscape reconfigured markedly: forest expanded from 52.4% (461.8 ha) in 1984 to 83.8% (738.4 ha) in 2024, whereas bog declined from 37.2% (327.9 ha) to 10.2% (89.8 ha). Despite this contraction, the reserve-level ecological index increased significantly over time, reflecting widespread greening and reduced surface exposure. However, bog condition was strongly climate-sensitive, with moisture signals remaining unstable and responses to warm/dry summers contrasting with those of forest and grassland. The results highlight that apparent greening can mask hydrological vulnerability and underscore the need for continued rewetting and control of woody encroachment.