Pollen in Polar Ice Implies Eastern Canadian Forest Dynamics Diverged From Climate After European Settlement

Rapid warming and human exploitation threaten boreal forests. Understanding links among vegetation, climate, and people in this vast biome requires highly resolved long-term records that integrate regional inputs. We developed an 850-year pollen-based record of supraregional vegetation change using a southern Greenland ice core and atmospheric modeling that identified the boreal and mixed-conifer forests of eastern Canada as the dominant pollen source regions. Conifer pollen increased similar to 1400 CE at the onset of the cooler and drier Little Ice Age. A subsequent decline began similar to 1650 CE and a statistically significant pollen change after 1760 CE suggests ecological consequences of the Little Ice Age cooling and initial human exploitation that persisted until recent decades. These supraregional changes are broadly consistent with local records and demonstrate intensification of human impacts on northern forests, suggesting a shift from a climate-modulated to an increasingly human-controlled system during recent centuries. Understanding the consequences of climate warming and human exploitation for northern forests requires long-term regional records of this sparsely populated region. We present a first 850-year vegetation record from a low-elevation ice core in Southern Greenland. The ice core integrates pollen from Eastern Canadian forests and other boreal forests, providing temporal precision and regional coverage not available from previous paleoecological investigations. We show that climate change drove changes in the abundances of coniferous species during the Little Ice Age. Subsequent warming coincided with the onset of timber exploitation that brought a shift from a climate-controlled to an increasingly human-controlled system. Current warming trends likely will further alter vegetation distribution, productivity, and disturbance regimes of northern forests, but they will be moderated by the legacy of human impacts. Atmospheric model FLEXPART identifies boreal and mixed-conifer forests in Canada as pollen source area for Southern Greenland ice corePollen in Greenland ice track conifer pollen increases similar to 1400 CE at the onset of the cooler and drier Little Ice AgeConifer pollen declines similar to 1650 CE coincident with cold LIA climate and initial commercial forest exploitation