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Rapid climate change increases wildfire activity

Published: 30 January 2009

There are clear links between sudden, rapid climate change and the incidence of wildfires, with abrupt climate changes generally marked by a shift in the level of burning as well as an increase in the incidence of fires, a new study shows.

The study, conducted by an international team of researchers, examines the response of fire activity in North America to sudden climate changes that occurred during the transition from glacial to interglacial conditions between 15,000 and 10,000 years ago.

The team, which includes Professor Mary Edwards of the School of Geography at the University of Southampton, who is an expert on the boreal forest of Alaska, concludes that when the climate warms abruptly, burning increases -as it appears to have been be doing again over recent decades.

To assess the change in fire activity during the last glacial-interglacial transition (LGIT), the researchers used 35 charcoal and pollen records from lake sediment across North America.

Charcoal data indicate an important role for climate and particularly rapid climate change in determining broad-scale levels of fire activity.  These data from lake sediments record the amount of biomass burning in general, and temporally detailed records can actually pick out individual fires thousands of years ago. The group's findings suggest that intervals of rapid climate change are marked by large increases in fire activity. 

Burning increased as conditions warmed during deglaciation until the beginning of the Younger Dryas cold interval 12,900 years ago. It levelled off during the cold interval, then increased again as warming resumed after the end of the cold interval 11,700 years ago.  The well-documented rapid climate changes of this time may therefore have triggered increased fire at a regional scale.

Importantly, the results do not support the recent hypothesis that a comet impact resulted in continent-wide wildfires at the onset of the Younger Dryas period.

An insight into whether rapid climate change has caused wildfires in the past will help scientists to understand whether present changes in global temperatures will cause more frequent fires in the future.

The results are published in the Proceedings of the National Academy of Science.

Notes for editors

 'Wildfire responses to abrupt climate change in North America' by JR Marlon; PJ Bartlein: MK Walsh; SP Harrison; KJ Brown; ME Edwards et al is published in Proceedings of the National Academy of Science, early edition, doi_10.1073_pnas.0808212106.

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