Many terrestrial organisms are currently shifting their distributions in latitude or in elevation, in response to a rapidly changing climate. Yet, the understanding of how these changes may impact ecosystem functioning in the long-term is unclear. To improve our predictions, we need to understand the mechanisms that cause ecosystem turnovers, which can be achieved by looking at potential analogues in the past. In this project, I use sedimentary ancient DNA to study Late Pleistocene and Holocene terrestrial ecosystem turnovers from lake sediments. I have generated over 100 shotgun metagenomics libraries for sediments from the Kullen Peninsula - one of the first areas of the Fennoscandian Peninsula to become ice-free after the Last Glacial Maximum, and approximately 20 shotgun libraries from a lake in northwestern Greenland in which I have a record that extends before the arrival of musk ox and humans on the island. I plan to reconstruct these ecosystems to understand how the terrestrial plant community composition may have been impacted by shifts in climate and the arrival of herbivores or humans.