Human impact and climate reconstructions from South American pollen records during the last 2000 years

Fossil pollen records are excellent indicators of human impact through time. Evidence for human land use in pollen records is useful for distinguishing natural from anthropogenically driven vegetation change. Here we discuss the variability and implications of human indicators in South American pollen records from the last two millennia. This period is also an important baseline for current climate as conditions were very similar to the present. We relied on records, where the degree of human impact on the vegetation is at a minimum or absent, and applied a qualitative approach to reconstruct climate in terms of temperature and hydrological balance. Interpretations for selected regions were made based upon the integration of different sources of information, including pollen records, climate models, plant-environmental interactions, archaeology, and additional proxy data. We conclude that pollen records allow assessing changes in the large-scale atmospheric circulation, butare also sensitive to local-scale variability. Long-distance synchronicity (differences and similarities) in vegetation changes are detected and interpreted as anindication of regional precipitation and temperature variability, though these patterns are more complex in mountainous regions. This study is part of the PAGES workgroup Long-term multi-proxy climate REconstructions and Dynamics in South America (LOTRED-SA). This collaborative long-term initiative offers the ideal framework for the integration of the various paleoclimatic sub-disciplines. Here we stress the high potential of pollen records as a valuable contribution to our understanding of tropical ecosystems in the context of the last two millennia.