Geology and landscape controls over Middle to Modern Age human frequentation in mountain environments: preliminary results from the Western European Alps.

Mountains are one of the best environments for the observation of the interaction between geology, landscape, and human sustenance strategies. In the Western European Alps, many areas have the potential to provide useful information on the relationship between geological diversity and human history, offering unique insights into settlement and activity patterns. Bedrock lithology, geomorphological features, soil development, and the overlying hydrological systems, directly shaped settlement distribution, agricultural and pastoral practices, and trade networks. Even in such difficult conditions, the more fertile valley floors provided stable and exploitable soils, while upland areas supported pastures and timber industries, vital for the survival of medieval economies. This study is part of the DAHU project (Programme INTERREG VI-A France-Italia ALCOTRA 2021-2027, n. 20108) and integrates geomorphological and soil surveys, paleoenvironmental reconstructions, and archaeological evidence to provide insights on how human frequentation throughout the Middle and Modern Age was influenced by landscape factors and the underlying geological setting.

The complex alpine communities within the closed area of the Vallone di San Grato (Valle d'Aosta region, NW Italian Alps) have been well established since the Middle Ages - at least since the colonisation of the Walser populations in the 13th-14th Centuries - and expanded over the centuries before their decline and disappearance, which became more and more evident from the 18th Century onwards. This frequentation left many traces in the form of built structures and settlements, as well as profound land modifications for cultivation, forestry, and pastoral activity.

Preliminary results allow to draw a first contextualization of the available archaeological and paleoenvironmental evidence inside their geological and geomorphological context. It is evident that medieval and modern communities were able to consume natural resources and deal with the many geological and landscape constraints on the territory, adapting settlement patterns, construction methods, and resource management accordingly. Above all, past glacial dynamics strongly dictated settlement choices, with most settlements located on moraine deposits and exploiting the soils in the less steep areas for cultivation, and leaving deep modifications in their morphology and chemical properties. Examples of land use are manifold and distributed throughout the valley, where only the steepest bare slopes were not utilized. Human impact also brought substantial land modifications through the centuries, especially on the higher slopes exploited for forestry, where the recent reactivation of slope processes hints at overexploitation-driven instability episodes.

This dynamic interaction offers insights into the resilience of medieval to modern alpine societies in responding to environmental challenges, with implications for cultural heritage preservation and sustainable development in similar landscapes.