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Wildfires closely linked to climate change

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The researchers analyzed the variation in wildfires in response to the abrupt climate change that took place between 13,000 and 11,000 years ago. The results provide valuable information about possible trends in wildfires in the future. These findings have been published on line in Proceedings of the National Academy of Sciences (PNAS) dated 3 February 2009.

The authors of the article studied the period from 15,000 to 10,000 years ago which was characterized by very large scale environmental change, similar to that which is emerging today. They reconstructed the history of wildfires between 15,000 and 10,000 BP (1) from sedimentary charcoal records. By studying fossil pollen, they were able to show that there was a major increase in plant biomass during the warming of the climate that took place from the end of the Younger Dryas (a period of cooling lasting from around 12,900 to 11,700 years ago). They were able to establish clear links between these two sets of data.

Biomass burning gradually increased until the beginning of the Younger Dryas. Although there are records of variation in fire activity between 12,900 and 11,700 BP, there is no evidence for any systematic trend at that time. However, there was a rapid increase in wildfires after the end of the Younger Dryas around 11,700 BP, in other words right at the beginning of the warm climate period known as the Holocene in which we are currently still living. The timing of changes in frequency of fires is neither coincident with emerging population change in human societies, nor with the timing of the extinction of herbivorous megafauna in North America, and even less so with a hypothetical meteorite bombardment, three factors which could have had an effect on the outbreak and spread of fires on a large scale.

The conclusions of the study emphasize the major environmental role played by climate change during a period of accelerated warming in determining broad-scale fire activity.

This study is a logical sequel to another study published in Nature Geoscience in October 2008 (2) which showed that the climate was a natural planet-wide driving force of the fire regime through the centuries that preceded the Industrial revolution.

This research implies that ongoing global warming, which is especially noticeable at temperate and northern latitudes, as well as the forest expansion resulting from major agricultural abandonment in industrialized areas, could promote the spread of climate-driven fires and lead to new societal and environmental risks.

(1) BP: years before present

(2) Marlon J.R., Bartlein P.J., Carcaillet C., Gavin D.G., Harrison S.P., Higuera P.E., Joos F., Power M.J. & Prentice I.C. (2008) Climate and human influences on global biomass burning over the past two millennia. Nature Geoscience 1, 697 - 702 (2008), doi :10.1038/ngeo313

Julien Guillaume | Quelle: alphagalileo
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