Search

Fire regime shifts are driven by climate and natural vegetation changes, but can be strongly affected by human land management. Yet, it is poorly known how humans have influenced fire regimes prior to active wildfire suppression. Among the last 250 years, the human contribution to the global increase in fire occurrence during the mid-19th century is especially unclear, as data sources are limited. Here, we test the extent to which forest management has driven fire regime shifts in a temperate forest landscape. We combine multiple fire proxies (macroscopic charcoal and fire-related biomarkers) derived from highly resolved lake sediments (i.e., 3–5 years per sample), and apply a new statistical approach to classify source area- and temperature-specific fire regimes (biomass burnt, fire episodes). We compare these records with independent climate and vegetation reconstructions. We find two prominent fire regime shifts during the 19th and 20th centuries, driven by an adaptive socio-ecological cycle in human forest management. Although individual fire episodes were triggered mainly by arson (as described in historical documents) during dry summers, the biomass burnt increased unintentionally during the mid-19th century due to the plantation of flammable, fast-growing pine tree monocultures needed for industrialization. State forest management reacted with active fire management and suppression during the 20th century. However, pine cover has been increasing since the 1990s and climate projections predict increasingly dry conditions, suggesting a renewed need for adaptations to reduce the increasing fire risk. [ABSTRACT FROM AUTHOR]

Climate and natural vegetation composition determine the biome-specific fire regimes, but shifts in regional to global fire regimes can also be strongly affected by human land management. Among the last 250 years, fire occurrence increased globally during the mid-19th century, which was explained mainly by natural changes, but also related to increased human population growth. Yet, it is poorly known how exactly humans have influenced fire regimes prior to active wildfire suppression, which led to a global decrease in fire occurrence since the onset of the 20th century. To improve predictions of current and future fire risk, the human dimension of fire regime shifts requires more interdisciplinary research.Here, we investigate the influence of climate, land cover change, and human activity on fire regimes in northern Poland using multiple highly resolved lake-sedimentary fire proxies (i.e., charcoal and the fire biomarkers levoglucosan and its isomers). Supported by a review of historical documents, we robustly classify source area- and temperature-specific fire regimes (biomass burnt, fire episodes). We find two prominent fire regime shifts during the 19th and 20th centuries, driven by an adaptive socio-ecological cycle in human forest management. Although individual fire episodes were triggered mainly by arson during dry summers, the biomass burnt increased unintentionally during the mid-19th century due to the plantation of flammable, fast-growing pine tree monocultures needed for industrialization. State forest management reacted with active fire management and suppression during the 20th century. Similar scenarios are likely also in other industrializing regions worldwide, where not only pine but also flammable Eucalyptus monocultures have been planted. In the light of climate projections that predict increasingly dry conditions, a renewed need for adaptations to increasing fire risks becomes necessary. [ABSTRACT FROM AUTHOR]

Fire regime shifts are driven by climate and natural vegetation changes, but can be strongly affected by human land management. Yet, it is poorly known how humans have influenced fire regimes prior to active wildfire suppression. Among the last 250 years, the human contribution to the global increase in fire occurrence during the mid-19th century is especially unclear, as data sources are limited. Here, we test the extent to which forest management has driven fire regime shifts in a temperate forest landscape. We combine multiple fire proxies (macroscopic charcoal and fire-related biomarkers) derived from highly resolved lake sediments (i.e., 3-5 years per sample), and apply a new statistical approach to classify source area- and temperature-specific fire regimes (biomass burnt, fire episodes). We compare these records with independent climate and vegetation reconstructions. We find two prominent fire regime shifts during the 19th and 20th centuries, driven by an adaptive socio-ecological cycle in human forest management. Although individual fire episodes were triggered mainly by arson (as described in historical documents) during dry summers, the biomass burnt increased unintentionally during the mid-19th century due to the plantation of flammable, fast-growing pine tree monocultures needed for industrialization. State forest management reacted with active fire management and suppression during the 20th century. However, pine cover has been increasing since the 1990s and climate projections predict increasingly dry conditions, suggesting a renewed need for adaptations to reduce the increasing fire risk., Competing Interests: The authors have declared that no competing interests exist.