Climatic variability and human impact during the Holocene from an Alpine peat bog

Abstract

It is scientifically well-established that the Earth's surface air temperature has warmed significantly during the past 150 years, and that an upward trend with a noticeable rapid temperature rise at the end of the 20th century is registered. In this framework of current global warming, mountain environments are particularly sensitive and vulnerable areas. European Alps registered in the last 150 years an exceptionally mean temperature increase of about 2°C, more than twice the average increase that characterized the warming of the Northern Hemisphere. The rapid climate change and the necessity of future projections require a deep understanding of the climatic system, ruled by natural forcing and affected by anthropogenic impacts. Therefore, insights in past climate variations, aiming at a better understanding of this complex system, are fundamental. Climatic information may be directly or indirectly registered in natural archives, e.g., ice cores, marine sediments, tree rings, lake sediments and peatlands. Among peatlands, ombrotrophic peat bogs, receiving water and nutrients exclusively from dry and wet atmospheric depositions, are one of the most suitable matrices for climate reconstruction, registering solely atmospheric conditions. The Coltrondo peat bog (46°39’28.37’’N 12°26’59.17’’E), located in the Eastern sector of the Italian Alps (Dolomitic area) was the subject of this research project and, through the analysis of different parameters, it allowed the reconstructions of past climatic and environmental variations as well as the impacts of human activities that characterized the Alps during the Middle and the Late Holocene. The selection of a multi-proxy approach included the investigation of physical, chemical and biological parameters. This strategy provided independent evidence about past climate changes and human impacts that characterized the last 7800 years cal BP, extending back to the Middle Holocene. Pollen analysis performed on the entire profile of the core, combined with the results of geochemical analyses (major and trace elements, rare earth elements and lead isotopes) allowed the reconstruction of different aspects of the past history recorded by the peat bog, achieving new insights into Holocene climate variability in the Eastern Italian Alps. Climatic oscillations were registered by the bog before human settlements in the area. Afterward, human pressure on the environment, mainly through agriculture, pasture and mining and, for the last century, industrial activities, makes it difficult to clearly divide the amplitude of Holocene climate natural variability from human-related changes. This work may be considered as a first fundamental step for the study of this area, adding valuable information about the climate and human history of Eastern Italian Alps, a strategic sector that needs further investigations.