Landslides and climate change in the Italian Dolomites since the Lateglacial

The paper deals with the relationship between the temporal occurrence of landslides and climatic changes in the period ranging from the Late-glacial to the present in the Italian Dolomites. After an introduction on the state-of-the-art, with particular reference to the Alpine region, and showing the promising aspects and main constraints of the research in this field, the results of recent investigations carried out in the two study sites are illustrated.The first study site is that of the Cortina d'Ampezzo, where several landslides have been identified and dated mainly by means of radiometric methods. The most ancient dates thus determined refer both to large rock slides which affected the dolomitic slopes after the withdrawal of LGM glaciers and to slides and flows mainly occurring on pelitic materials of the valley floors (from 13,000 to 10,000 cal. yr BP).Other datings allowed a series of flows which developed between 5500 and 2500 yr BP to be detected. For the latter, though, it was not possible to define whether they were reactivations of ancient mass movements or first-time landslides. In the Alta Val Badia the most ancient events go back to 10,000 and 9000 yr BP. In particular, they correspond to earth flows following vast rotational slides affecting the bedrock up to a depth of about 50 m. More recent earth flows, involving more modest amounts of material, took place some 5000 to 2000 yr BP.By analysing the dates so far obtained in the two study areas, it was possible to correlate the recorded increase of landslide activity with the climatic changes occurring at the boundary between the Lateglacial and the Holocene and between the Atlantic and the Sub-Boreal. The types and causes of landslides taking place in these two periods are, in any case, substantially different with respect to the different morphoclimatic conditions which existed in the two areas when these mass movements were triggered. Nevertheless, the Cortina d'Ampezzo area and the Alta Val Badia were affected by landslides also in other periods of the Holocene. This fact witnesses the importance of non-climatic causes, such as geological-structural factors. Notwithstanding this, by considering the results obtained it may be stated that many dated landslides can be considered as indicators of climatic changes.