Northern Norway paleofire records reveal prehistoric human impacts on fire activity

• Main Author: Topness, Rebecca
• Format: Text
• Language: unknown
• Published: W&M ScholarWorks 2022
• Subjects: Geology; Lofoten; Norway; Fennoscandia; Northern Norway
• Online Access: https://scholarworks.wm.edu/geologyseniors/31; https://scholarworks.wm.edu/context/geologyseniors/article/1035/viewcontent/RebeccaTopness_SeniorThesis_Geology_2022.pdf

Paleofire records demonstrate how Holocene fire activity in Fennoscandia varied in response to climate and human activities, offering insights into climate-fire relationships and the expected response of fire to anthropogenic climate change. Molecular biomarkers such as polycyclic aromatic hydrocarbons (PAHs) could expand on existing fire proxies, like charcoal and fire scars, to resolve additional fire characteristics and reveal new trends. PAHs are a group of chemical compounds produced during the burning of organic matter. They provide direct evidence of fire in the geologic record as well as preserve information about transportation and fuel source. This study combines multiple PAH records and a charcoal record derived from three lake sediment cores from the Lofoten Islands, Norway to provide a comprehensive assessment of Holocene paleofire in northern Norway. All three lake sediment records show an overall increase in PAH accumulation rate over the past c. 7500 cal yr BP, ranging from 0 to 46.3 ng/g/yr. Low values in the early Holocene (7500-5000 cal yr BP) reflect the natural fire signal driven by changes in climate prior to the influence of human activity. An abrupt increase in values, particularly low molecular weight PAHs, at c. 5000 cal yr BP that reach a maximum c. 2000 cal yr BP correlates with the initial establishment and expansion of human settlements and agriculture in Lofoten. The late Holocene (1000 cal yr BP-present) is characterized by a distinct increase reaching the highest values over the record, which reflects regional industrialization. Two charcoal size fractions were quantified (>125 μm and 63-125 μm) and support these trends. Published paleofire data were compiled and re-evaluated to place the Lofoten records in context of broader Fennoscandia. These results have implications for understanding human influence on fire activity in Lofoten and connections between fire and climate.