Climate drives wildfire activity
The biggest overall influence on global wildfire activity in the last 2,000 years has been climate, according to a new study that also shows humans have played a significant role in fire levels in recent centuries.
Researchers looked at charcoal levels in hundreds of corings of ancient lake sediments and peat from around the world.
What they found is that until about 1750, there was a long-term decline in burning, reflecting a global cooling trend. Then, as global settlement expanded and the Industrial Revolution took hold, wildfires increased, peaking around 1870. Farmers used fire to clear the land. Increased fossil-fuel use contributed to rising levels of carbon dioxide that sped plant growth and created more to burn. More people meant more fires started by humans.
But starting in the late 19th century, settlement had the opposite effect, particularly in western North America, the tropics and Asia.
Livestock ate the native grasses that had helped fuel frequent, low-intensity fires in the West. Wildlands were replaced by farms. During the 20th century, fire suppression became the norm in many parts of the world.
The result was an abrupt drop in fires, despite a warming climate.
The paper, "Climate and Human Influences on Global Biomass Burning over the Past Two Millennia," was published online Sunday in the journal Nature Geoscience and was written by a nine-member team from the U.S., Europe and Great Britain.
It did not take into account recent decades, when wildfires in the U.S. have been on the rise.
Patrick Bartlein, a University of Oregon geography professor and one of the study authors, said climate is regaining the upper hand as the dominant force.
"All signs point to the idea that with continued global climate change ... we'll see more and bigger” fires.
-- Bettina Boxall
Photo: Firefighters working on the 2007 Big Bear blaze. Credit: Brian Vander Brug / Los Angeles Times