Contrasting trends of greening in the waning snowfields of the Hindu-Kush Karakoram Himalaya

In cold mountain areas, plant growth is limited by temperature and seasonal snow cover, with vegetation activity starting only after snow melts. Earlier snow disappearance extends the snow-free period and exposes plants to warmer conditions, increasing opportunities for vegetation activities. The Hindu Kush–Karakoram–Himalaya (HKKH), one of Asia’s largest and fastest-warming mountain systems, has experienced snow melting earlier by 4.37 ± 3.67 days. Using nearly three decades of Landsat satellite observations combined with ERA5-Land climate data, we measured changes in Snow Melt-Out Date (SMOD; day of year when seasonal snow disappears), annual maximum Normalised Difference Vegetation Index (NDVImax), and Growing Degree Days (GDD; cumulative temperature from SMOD to the end of the study period) across seasonally snow-covered regions above the treeline. Our study shows that approximately 80% of waning snowfields in HKKH shows increasing greenness, especially in pixels that were previously sparsely vegetated. At the same time, heat accumulation during snow-free days has increased by more than 50% due to earlier snowmelt between 1994–2005 and 2013–2024. These results highlight interactions between seasonal snow, temperature, and vegetation, emphasising the importance of including snow dynamics in climate adaptation strategies for mountain ecosystems.