High alpine ponds shift upwards as average temperatures increase : a case study of the Ortles-Cevedale mountain group (Southern Alps, Italy) over the last 50 years

Alpine ecosystems are especially vulnerable to climate change, and lakes and ponds act as early indicators. Here, we describe our findings for the Ortles–Cevedale mountain group (Stelvio National Park, Southern Alps, Italy), where we used remote sensing to analyze more than 100 water ponds over the last 50 years (1954–2007). We found that since the 1980s, some lower elevation ponds (< 2500 m a.s.l.) have disappeared or experienced surface area reduction. We link this impact to the increased evaporation/precipitation ratio associated with climatic warming. At higher elevations (> 2900 m a.s.l.), we observed that since the 1950s, ponds have increased in size and that new ponds have appeared as a consequence of glacial shrinkage and retreat. However, these new ponds are ephemeral. The appearance of new environments is usually followed by their rapid disappearance and by a concomitant appearance of new ones, which is a clear sign of a transition from a glacial system to a paraglacial system. Surface area changes have been shown to be a highly visible and easily measurable signal of the impact of climate change on the alpine environment, as already demonstrated in other remote areas of the world. There is a clear need to extend this analysis to other sites in the Alps to gain a regional understanding of the phenomenon. The findings of this study make it possible to interpret the variations created by climate change in these environments, in terms of alteration of their ecological role and the loss of ecosystem services.