Western Wildfires Getting Worse in a Warming World

July 9, 2012

Western Wildfires Getting Worse in a Warming World
The vicious 2012 wildfire season now unfolding in the interior West is hardly a surprise. Much of the region has been in a drought for more than a decade. This winter’s snowpack was sparse, particularly in Colorado, and it melted and ran off early. Temperatures have been high, and humidity has been low—making fuels from grasses to trees very dry and flammable.

It’s impossible to link any one particular fire or weather event to climate change. In the case of fires in the West, there are other factors as well: more people living in fire-prone areas in and near forests and unnaturally crowded forests brought on in large part by decades of misguided efforts to battle and suppress nearly all fires.

Robust statistical associations between wildfire and hydroclimate in western forests indicate that increased wildfire activity over recent decades reflects sub-regional responses to changes in climate. Historical wildfire observations exhibit an abrupt transition in the mid-1980s from a regime of infrequent large wildfires of short (average of 1 week) duration to one with much more frequent and longer burning (5 weeks) fires. This transition was marked by a shift toward unusually warm springs, longer summer dry seasons, drier vegetation (which provoked more and longer burning large wildfires), and longer fire seasons. Reduced winter precipitation and an early spring snowmelt played a role in this shift.

The great irony of the decades of aggressive fire suppression is that in many parts of the West it has made fires larger and more destructive. For example, the mid-elevation Ponderosa Pine forests that cover much of the West historically had frequent fires of low intensity that removed undergrowth but spared larger, thick-barked trees. Firefighting efforts prevented those small cleansing fires and allowed forests to become overcrowded with small trees and underbrush that now fuel larger, more catastrophic fires.

https://www.americanprogress.org/issues/green/news/2012/07/09/11889/western-wildfires-getting-worse-in-a-warming-world/