Detecting long-term canopy change and vegetation shifts in northern peatlands using LAI and climate data

Abstract. Peatlands store vast amounts of carbon, yet their canopies are changing under northern warming. We assessed recent vegetation trajectories by analysing greening and browning across northern peatlands using a gap-filled, sensor-independent climate data record of leaf area index (LAI) for 2001–2023. To our knowledge, this provides the first multi-decadal, peatland-specific assessment of canopy trends based strictly on mapped peatlands. Although greening was widespread at the pixel level (77 % of peatlands; greening-to-browning ratio 3.5:1), the area-weighted LAI trend at the map scale was not significant. LAI anomalies were weakly positively correlated with temperature and weakly negatively correlated with precipitation. Higher tree cover was associated with less greening, with a smaller effect observed in areas with deciduous needleleaf forests and under higher precipitation. Decadal variability left a regional, non-linear imprint: most pixels showed no breakpoints, but where present they often were temporally aligned with phase shifts in the Pacific Decadal Oscillation (PDO). Cup-shaped trends were concentrated in West Siberia, whereas hat-shaped trends were widespread across Europe, northeastern Asia, and Canada. Protected peatlands did not show different LAI trends when differences in climate and canopy were taken into account. Overall, recent peatland canopy change was not a uniform increase in greenness but reflected moisture-sensitive, composition-dependent responses modulated by decadal climate variability. Together, these results provide a circumpolar, peatland-specific baseline that clarifies where and why LAI is changing and enables evaluation of how moisture conditions, decadal variability, canopy composition, and protection status relate to recent canopy trajectories in northern peatlands.