There have always been climate variations over time. Whether it be through natural causes as in the distant past or today through combination with human activity, climate change has far-reaching consequences. The Oeschger Centre investigates the effects of climate change on water supply, snow, ice, and natural hazards, but also on natural and managed ecosystems such as agriculture. Past and present contain valuable insights for the future, for example in Willy Tinner's work. He studied geography, geobotanics and archaeology and is Professor of Palaeoecology. His research group focuses on the spread of certain types of tree species and other plant communities as a reaction to climate change. Have certain species increased, decreased, or even become extinct over time? In order to find answers to these questions, Willy Tinner studies lake sediments. These contain pollen, charcoal particles and other microfossils. The analysis of these findings reveals information about the long-term interplay between climate, the biosphere and human activity. The palaeoecological data are compared to models which can simulate the dynamics of vegetation over a period of decades or even thousands of years. In this way, Willy Tinner can test hypotheses on which factors affect which type of ecosystem in the long term. This combined method of data reconstruction and computer modelling enables predictions as to how certain species of tree will react to climate change in future. For example, which trees will spread from southern to northern Europe and within what time frame?