The priority programme ''Changes of the Geo-Biosphere'' aimed to reconstruct the environmental history of central Europe with emphasis on the time interval from 9000 to 5500 cal BP (time-slice II), coinciding with the Holocene climatic optimum. During this period, the onset of human activities such as settlement, agriculture and animal husbandry caused environmental changes. Studies of different landscape units in Germany were carried out to identify these anthropogenically induced changes and to distinguish them from natural effects on the environmental system. The investigated archives included laminated lake sediments, fluvial sediments, colluvia and soils, speleothems, peat and coastal sediments. The different archives were examined using refined research methods including a variety of sedimentary and geochemical analyses, together with pollen analysis and dating methods for the establishment of a reliable chronology. The results of the various research groups are summarised and critically discussed. Based on these results, the climatic optimum can be subdivided into three periods: (1) the Early Atlantic from 9000 to 7500 cal BP with negligible human impact and stable environmental conditions; (2) the Late Atlantic during Early and Middle Neolithic from 7500 to 6300 cal BP with pollen evidence for vegetation changes but only negligible changes detectable in other proxy records; and (3) the Late Atlantic during the Younger Neolithic (Jungneolithikum), after 6300 cal BP, with human impact observed in many archives and proxy records especially in the pollen record but also in lacustrine and fluvial sediments. During the whole climatic optimum natural causes, such as minor shifts of temperature, did not induce substantial environmental changes, though some changes, such as temporary droughts, may have facilitated and amplified the observed human impact. r
The vegetation of the northern Upper Rhine Graben (southwestern Germany) is reconstructed for the end of the Lateglacial and the Holocene by means of palynological analyses in combination with AMS 14c dating. Analogous to adjacent lowland areas, the Younger Dryas climatic deterioration did not result in a complete deforestation of the area and open pine woodlands with locally birch stands and shrubs persisted. A subdivision of the Younger Dryas period, into a humid first phase, followed by a dry second phase was also reflected in our records. For the Holocene, the pollen diagrams show two regionally different vegetation developments, related to substrate and variations in annual precipitation: in the south the ‘classical’ succession of pine then hazel is followed by other deciduous trees, whereas in the northern part, pine kept its dominance far into the Subboreal.
In climatically sensitive regions such as the Northern Alps, changes in climate and land use have a strong impact on landscapes, vegetation, animals and humans. Multidisciplinary investigations in the high St Antönien Valley (Switzerland) at 1400—3000 m a.s.l. have generated a reconstruction of land-use history. Humans began affecting the landscape of this high mountain region during the Bronze Age. Multiproxy palaeoenvironmental studies show that the present cultural landscape of the valley has been the result of long-term human environmental interactions. Pollen, soil and tree analyses were combined with archaeological and historical archives to provide strong evidence of the complexity of the high-mountain land-use system over the last 3500 years. Phases of agro-pastoral activity from Bronze Age (around 1300 BC), Iron Age (800—15 BC), Roman Period (15 BC—AD 450) and Middle Ages (AD 450—1500) are linked to climate and economic, social and cultural developments. Our results reveal that expansions of pasture land, in combination with climatic fluctuations, led to pronounced ecological changes in St Antönien Valley. Humans adjusted land-use practices according to changing environmental conditions. In this context, the use of fire was an important factor in land management. Forest clearances reached maximum intensity during the late Middle Ages (AD 1300—1500) and triggered natural catastrophes that were amplified during the most severe environmental phase (AD 1600—1850) of the ‘Little Ice Age’ (LIA).
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