Ancient plant DNA reveals High Arctic greening during the Last Interglacial

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 (Pearson et al., 2013). 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 21st century
temperature change (Otto-Bliesner et al., 2013; Post et al., 2019).
However, high-latitude terrestrial records from this period are rare, so
LIG vegetation distributions are incompletely known. Pollen-based
vegetation reconstructions can be biased by long-distance pollen
transport, further obscuring the paleoenvironmental record. Here, we
present the first LIG vegetation record based on ancient DNA in lake
sediment and compare it with fossil pollen. Comprehensive plant community
reconstructions through the last and current interglacial (the Holocene)
on Baffin Island, Arctic Canada, reveal coherent climate-driven community
shifts across both interglacials. Peak LIG warmth featured a ~400-km
northward range shift of dwarf birch, a key woody shrub that is again
expanding northward. Greening of the High Arctic—documented here by
multiple proxies—likely represented a strong positive feedback on
high-latitude LIG warming. Authenticated ancient DNA from this lake
sediment also extends 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.