Last week, a sobering milestone was reached along the west slope of the Sierra Nevada - over a million acres burned since the start of this decade. 2000 to 2009 remains the decade with the highest number of acres burned in recorded history, but with the growth of the Rough Fire last week, our current decade took over as number two. On top of that, this is our sixth fire season in the current decade, and we still have four to go.
Prior to 1900, more acreage in the Sierra would have burned than we’re seeing now (approximately 500,000 acres a year), but many of the fires today are much more destructive. The larger burned areas of the past resulted from numerous smaller fires that generally burned low to the ground and moved slowly through the forest. Because forest conditions have changed, a higher number of acres are now being consumed by extremely large fires which are burning fast and with higher severity (Mallek et al., 2013). For example, in less than one day approximately 50,000 acres burned in the 2014 King Fire, and over 70 percent of those acres burned at high severity.
Seventy percent of the acreage that has burned since 2010 burned in just 10 large fires. The Rim Fire, King Fire, Chips Fire, Bagley Fire, Bald Fire, Eiler Fire, Reading Fire, Ponderosa Fire, American Fire, and now the Rough Fire account for nearly 800,000 acres burned in the last five years. The other 286,000 acres that burned between 2010 and today burned in 376 fires. If we compare these numbers with past decades, we find that almost the opposite was true historically.
Over the last 100 years, the Sierra Nevada landscape has been dotted by numerous small-acreage fires, not a few extremely large fires, as shown in this animation. For example, if we compare the size and number of fires from the 1950s with the current decade, there were almost 100 more fires in the 1950s, but they burned half the acreage of today’s fires.
The Rough Fire in the Southern Sierra is now the largest active fire in California, and it continues to grow. The Butte Fire in Calaveras and Amador Counties started on the afternoon of September 9 and grew over four thousand acres in less than 24 hours. It has now topped 70,000 acres and continues to burn. Conditions in the Sierra are such that within the next year we may overtake the previous record for number of acres burned in a decade, if current trends continue.
To reverse this trend, we must take action now to return our forests to a more resilient condition. Restoring our forests and reducing the risk for fires to grow quickly and burn at high severity will return the Sierra to a more historic and fire-adapted state. If we act this year, 20 years from now we may still see 200,000 acres of burned landscape a year, but we’ll be able to describe them as 200,000 restored acres rather than 200,000 scorched acres.
To download current versions of the charts featured on this blog, please visit the State of the Sierra Nevada's Forests graphs and charts page.