Northern Norway paleofire records reveal two distinct phases of early human impacts on fire activity

Abstract

Paleofire records document fire’s response to climate, ecosystem changes, and human-activity, offering insights into climate-fire-human relationships and the potential response of fire to anthropogenic climate change. We present three new lake sediment PAH records and a charcoal record from the Lofoten Islands, Norway to evaluate the Holocene fire history of northern Norway and examine human impacts on fire in this region. All three datasets show an increase in PAH accumulation rate over the past c. 7500 cal years BP, with an increase c. 5000 cal years BP that signals initial human impacts on fire activity. More significant increases c. 3500 cal years BP reach a maximum c. 2000 cal years BP that correlates with the establishment and expansion of agricultural settlements in Lofoten during the Late Bronze Age and Pre-Roman Iron Age. Decreased PAH accumulation rates c. 1500–900 cal years BP reflect less burning during the Late Iron Age and early medieval period. A shift toward higher molecular weight PAHs and increasing PAHs overall from c. 1000 cal years BP to present, reflects intensified human activity. Sedimentary charcoal (>125 and 63–125 µm) in the Lauvdalsvatnet record does not vary until an increase in the last 900 years, showing a proxy insensitivity to human-caused fire. The Late-Holocene increase in fire activity in Lofoten follows trends in regional charcoal records, but exhibits two distinct phases of increased fire that reflect the intensity of burning due to human landscape changes that overwhelm the signal of natural variations in regional fire activity.