Composition and Distribution of Supraglacial Vegetation on the Debris-Covered Belvedere Glacier, Italian Alps

Characteristics of plant growth on the surface of debris-covered glacier (DCGs) include the unstable and partly mobile ground caused by ice changes, frequent disturbances and high daily temperature fluctuations. Despite these seemingly limiting factors, supraglacial debris is known to host high biodiversity and, in some locations, where certain debris thickness and stability is reached, even forests. Furthermore, underlaying ice and warm rock-substrate can create microclimates enabling plants to grow outside their common elevational distribution. This unique characteristic has raised questions regarding the role of DCGs as refugias for plants under changing climates. Despite expected increase in supraglacial debris coverage and long-term threat of survival due to global warming, research on vegetation on glaciers remains limited. Through a combined approach of field surveys and remote sensing analyses, insights on plant species composition, distribution and prevalence of these ecosystems can be gained, providing information on the role and significance of supraglacial vegetation in alpine environments and as habitat for species threatened by climate warming.

During the summer of 2025, vegetation sampling was conducted on 21 plots of 10 m² each on the Belvedere Glacier below the east face of Monte Rosa (Italian Alps). With the use of high spatial resolution drone imagery, vegetation cover on selected areas was detected via supervised classification methods. Orthophotos derived from aerial photography (SWISSTOPO) were used to delineate and to investigate the spatial pattern and distribution of vegetation along the entire glacier tongue based on normalized differenced vegetation index (NDVI) analysis.

Supraglacial vegetation was detected from the two terminal glacier lobes at about 1840 m a.s.l. up to an elevation of 2140 m a.s.l., where slope angle of the glacier strongly increases. Vegetation ground cover of the 21 plots averaged at 28 % with extreme outliers of 0.25% (highest elevation) and 97% (medium elevation). In total, 64 vascular plant species were identified. The NDVI analysis revealed an increase of supraglacial vegetation from the year 2017 to 2023. Due to the small size and sparse distribution of vegetation patches, vegetation coverage is generally underestimated on the drone images and orthophotos.