The Exceptional U.S. Wildfire Season of 2012

[phantom power]

The 2012 U.S. fire season was the 3rd worst in U.S. history, with 9.2 million acres burned--an area larger than the state of Maryland. Since the National Interagency Fire Center began keeping records in 1960, only two years have seen more area burned--2006, when 9.9 million acres burned, and 2007, when 9.3 million acres burned. Although the 2012 fire season was close to a record for most acreage burned, the total number of fires--55,505--was the lowest on record, going back to 1960, said scientists at a December 2012 press briefing at the American Geophysical Union meeting in San Francisco. The average U.S. fire size in 2012 was the highest on record. A September 18, 2012 report, The Age of Western Wildfires, published by the non-profit research group Climate Central, found that the number of large and very large fires on Forest Service land is increasingly dramatically. Compared to the average year in the 1970s, during the past decade there were seven times as many fires larger than 10,000 acres each year, and nearly five times as many fires larger than 25,000 acres. On average, wildfires burn twice as much land area each year as they did 40 years ago, and the burn season is two and a half months longer than 40 years ago. The increase in large fires is correlated with rising temperatures and earlier snow melt due to climate change, but fire suppression policies which leave more timber to burn may also be a factor.

http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=2320


Figure 10. Predicted fractional change in fire probability for the period 2010 - 2039 (top) and 2070 - 2099 (bottom) for the average of sixteen climate models used for the 2007 IPCC report. For the 2010 - 2039 period, the models agree that 8% of Earth will see decreases in fire probability, 38% will see increases, and the models are too uncertain to tell for the other 54%. For the 2070 - 2099 period, the models agree that 20% of Earth will see decreases in fire probability, 62% will see increases, and the models are too uncertain to tell for the other 18%. Image credit: Climate change and disruptions to global fire activity, Moritz et al., 2012, from the journal Ecosphere.

[NickB79]

1. Invasive cheatgrass is also playing a major role

Not sure if you've read this, but I found it pretty interesting: http://www.latimes.com/news/science/sciencenow/la-sci-sn-cheatgrass-increases-wildfire-20121205,0,4091697.story

When a team of academic researchers blended wildfire data with satellite images from the Great Basin, they confirmed what public land managers and ranchers have seen on the ground for years: cheatgrass, an invasive grass accidentally introduced by settlers more than a century ago, is fueling bigger, more frequent wildfires in that empty stretch of the West.

Comparing regional land cover maps with the dates and boundaries of Great Basin wildfires, the researchers found that fires in areas dominated by cheatgrass consistently ranked as the largest or second largest. Of the 50 biggest fires recorded in one dataset from 2000 to 2009, 39 involved cheatgrass. The invasive covered 6% of the landscape, but 13% of the burned land, giving it an outsized role in the largest fires.

snip

A short-lived annual that is dead most of the year, the exotic grass doesn’t provide the nutrients or wildlife shelter that natives do, ultimately stripping land of its biodiversity.

It ignites easily and burns quickly, fueling fires that incinerate sagebrush, pinyon-juniper woodlands and other native plants. “As sites burn, more and more of them are likely to become cheatgrass grasslands, thus increasing their future probability of burning,” wrote the study authors, who were from Penn State, the University of Massachusetts-Amherst, UC Santa Barbara and University College London.