Ancient sedimentary DNA reveals a more biodiverse ancient Ireland.

The island of Ireland has been highlighted as one of the most nature depleted areas on Earth1, however it has significant potential for largescale nature restoration2. However, there remains uncertainty around which species naturally colonized Ireland after the last glacial maximum period, particularly large herbivores3. This study reports an ancient sedimentary DNA record from the Mesolithic in Ireland (10,000 years ago) up to the present day, from a lake core taken at Lough Feeagh, in the West of Ireland. The plant DNA results reveal a changing landscape, with hazel and oak being dominant in the early Holocene, with the highest diversity of tree species in the Bronze age, and also builds on previous work suggesting hornbeam may be a native tree. The mammalian DNA detected confirms many known Irish species such as red deer, wild boar and wood mouse, and suggests the later survival of some arctic fauna into the Holocene, namely reindeer and arctic fox. It also suggests the possible presence of aurochs in early Holocene Ireland. Aurochs were keystone species in ancient Europe4, but definitive evidence of their presence in Ireland has previously been lacking. Additionally, the DNA record for fish confirms a number of known species, such as Atlantic salmon and stickleback, but also suggests that pike may have been in Ireland earlier than conventionally accepted. These findings open up new possibilities for the restoration of nature in Ireland, revealing a more biodiverse baseline for restoration efforts to benchmark against