Accelerating climate change impacts on alpine glacier forefield ecosystems in the European Alps

In the European Alps the increase in air temperature was more than twice than the increase in global mean temperature over the last fifty years. The abiotic (glacial) and the biotic components (plants and vegetation) of the mountain environment are showing ample evidence of climate change impacts. In the Alps most small glaciers (80% of total glacial coverage and an important contribution to water resources) could disappear in the next decades. Recently climate change was demonstrated to affect higher levels of ecological systems, with vegetation exhibiting surface area changes, indicating that alpine and nival vegetation may be able to respond in a fast and flexible way in response to 1-2°C warming. We analysed the glacier evolution (terminus fluctuations, mass balances, surface area variations), local climate and vegetation succession on the forefield of Sforzellina Glacier (Upper Valtellina, Central Italian Alps) over the past three decades. We aim to quantify the impacts of climate change on coupled biotic and abiotic components of high alpine ecosystems, to verify if an acceleration is occurring on them on the last decade (i.e.: 1996-2006) and to assess whether new specific strategies were adopted for plant colonization and development. All the glaciological data indicate that occurred a glacial retreat and shrinkage which was much stronger since 2002 than during the last 35 years. Vegetation started to colonize surfaces deglaciated for only 1 year, with a rate at least 4 times greater than that reported in the literature for the establishment of scattered individuals and about two times for the well established discontinuous early successional community. The colonization strategy changed: the first colonizers are early successional, scree slopes and perennial clonal species with high phenotypic plasticity rather than pioneer and snow bed species. This impressive acceleration coincided with only slight local summer warming (c. +0.5°C) and a poorly documented local decrease in the snow cover depth and duration. Are we facing accelerated ecological responses to climatic changes and/or did we go beyond a threshold over which major ecosystem changes may occur in response to even minor climatic variations