Ecological changes and human interaction in Valcamonica, the rock art valley, since the last deglaciation

Valcamonica is known all over the world for the development of rock art between the Lateglacial and the Middle Ages. We present here an updated synthesis on the environmental history of Valcamonica, focussing on the relationships between natural ecosystems, climate and human peopling. Among the natural archives reviewed, a reference is the Pian di Gembro succession, a middle-altitude site offering a chronologically and taxonomically highly-resolved ecological investigation for the last 15.5 cal ka BP. For this site we present quantitative reconstructions of climate parameters obtained from fossil pollen spectra. The deglaciation of the valley floor occurred about 18-17.5 cal ka BP. Remnants of a hut and rock engravings, referred to the Upper Paleolithic, are indication of human groups on the valley floor, possibly related to hunting activities on wild mammals sheltering in newlyestablished pine and larch forests. Lowering of the timberline and expansion of xerophytic formations affected the montane and subalpine belts in the Younger Dryas. Fast afforestation and timberline rise mark the Holocene onset, as a result of abrupt climate improvement. A phase of hemisphaeric climate change, also recorded in ice cores at 8.2 cal ka BP, promoted the expansion of spruce and fir at middle altitudes. Very high treeline altitudes (> 2,600 m asl) were withstood between 9.1-7.4 cal ka BP, as testified by finds of Pinus cembra trunks and seeds of relevant age in high-altitude mires. In this span, high-altitude camps of Mesolithic hunters, moving seasonally from the valley floor, left traces of forest fires, in the forms of charcoal fragments from hearths and pits with heat-fractured pebbles. Archaeological and palaeoecological data suggest peopling discontinuity between 7.5 to ca. 6.5 cal ka BP, when farming started to develop. The oldest cereal pollen grain is detected at ca. 6 cal ka BP, consistently with the cultural chronology of early settlements in Valcamonica. Mountain pastoralism is documented only for later periods (Bronze Age onward) but detecting earliest traces high-altitude husbandry needs further research at subalpine areas preserving natural archives. Alpine pastures and cereal fields further expanded since the Early Bronze Age, despite a poor archaeological record for the period. During the first millennium BC rock art spread across Valcamonica. Iron Age and Roman time display high rates of forest exploitation, often related to iron-smelting activities, and agriculture expansion. Chestnut and walnut appear between the I BC - II AD centuries.