Ancient DNA in lake sediment reveals High Arctic greening during the Last Interglacial

Abstract:

Summer warming is driving a greening trend across the Arctic, with the potential for large-scale amplification of climate change due to vegetation-related feedbacks. Because observational records are sparse and temporally limited, past episodes of Arctic warming can help elucidate the magnitude of vegetation response to temperature change. The Last Interglacial (LIG; 129,000–116,000 years ago) was the most recent episode of Arctic warming on par with predicted temperature change by the end of this century. However, high-latitude terrestrial records from this period are rare, so LIG vegetation distributions are incompletely known. Vegetation records based on pollen can be biased by long-distance pollen transport, further obscuring paleoenvironmental insights. Here, we show that plant DNA in lake sediments (sedaDNA) sensitively records the dominant shrubs locally present within high-latitude lake catchments and then apply this emerging proxy downcore through multiple interglacials. We present the first LIG vegetation record based on both lacustrine sedaDNA and fossil pollen. Comprehensive plant community reconstructions through the LIG and Holocene on Baffin Island, Arctic Canada, reveal coherent successional and climate-driven community shifts across both interglacials. Peak LIG warmth was marked by a ~400-km northward range shift of dwarf birch, a key woody shrub that is again expanding northward. Greening of the High Arctic—documented by both sedaDNA and pollen in our lake sediment core—likely represented a strong positive feedback on high-latitude warming and thus ice-sheet retreat during the LIG. Authenticated ancient DNA from this lake sediment record also pushes back the useful preservation window for the technique and highlights the utility of combining traditional and molecular approaches for gleaning paleoenvironmental insights to better anticipate a warmer future.