ScienceDaily Feb. 14, 2012 — The American West has seen a recent increase in large wildfires due to droughts, the build-up of combustible fuel, or biomass, in forests, a spread of fire-prone species and increased tree mortality from insects and heat.
Researchers from the University of Oregon’s Geography Department used historical charcoal data to analyze past fires. They concluded that
climate and people affect the present-day landscapes and forests of the American West, and …. they may change in the future..
Key findings of the study include
warm, dry intervals, such as the “Medieval Climate Anomaly” between 1,000 and 700 years ago, which had more burning, and cool, moist intervals, such as the “Little Ice Age” between 500 and 300 years ago, had fewer fires
Wildfires during most of the 20th century were almost as infrequent as they were during the Little Ice Age, about 400 years ago. However, only a century ago, fires were as frequent as they were about 800 years ago, during the warm and dry Medieval Climate Anomaly. “In other words, humans caused fires to shift from their 1,000-year maximum to their 1,000-year minimum in less than 100 years,”
Climate and humans acted synergistically — by the end of the 18th century and early 19th century — to increase fire events that were often sparked by agricultural practices, clearing of forests, logging activity and railroading.
These conclusions indicate that the current level of wildfires should be much higher due to dry conditions and the build-up of fuels. Fire suppression activities are “unsustainable” and we should expect more nasty fires to occur.
“Recent catastrophic wildfires in the West are indicators of a fire deficit between actual levels of burning and that which we should expect given current and coming climate conditions. Policies of fire suppression that do not account for this unusual environmental situation are unsustainable.”