Graph of the Day: Wildfire Season Length in the U.S. West, 1970-2011
During the past 40 years, wildfires have started earlier in the year and have continued to burn later in the year, lengthening the overall “burn season.” This figure illustrates the start date of the first wildfire each year on USFS land and the start date of the last recorded fire. The inset shows how the average time span between these two dates has increased by about 75 days since 1970. This analysis adds to an existing body of research that analyzed changes in Western wildfire trends up until 2003. Anthony Westerling of the University of California at Merced and colleagues have previously shown that in the mid-1980s, trends in large wildfires (more than 1,000 acres) changed suddenly and markedly; fires began burning more frequently, raged over larger areas, lasted longer, and the overall length of the wildfire season increased dramatically.3 With our additional consideration of more recent years, up to and including 2011, it is clear that the trend toward more and bigger fires is continuing.
