The potential for the largest fires – responsible for the lion’s share of burned area across the country – is expected to increase due to more explosive weather conditions and an ever-lengthening wildfire season.
On Wednesday, NOAA published a map which shows up to a 600 percent increase in the number of weeks at risk of very large fires by the 2041-2070 period in the Northern Rockies. Vast areas of the Mountain West, including the Great Basin, Sierra Nevada, and Pacific Northwest see the risk of very large fires increasing by 200 to 500 percent.
These results were obtained using the average results of 17 climate model simulations that assume rapidly increasing greenhouse gas emissions.
Average temperatures warm substantially under this scenario while, during the summer dry season in the West, precipitation and humidity markedly decrease. This results in drastically decreased soil moisture and tinderbox conditions prone to the largest of fires, defined as those in the top 10 percent.
The study’s results are consistent with those published in a recent report from the Environmental Protection Agency (EPA) which found, by the end of the century, twice as much land burning per year – representing an area exceeding the size of Massachusetts.
The NOAA-funded study, published in the International Journal of Wildland Fire, suggests the projected wildfire increase may have enormous costs:
Very large fires often require prolonged fire suppression commitments of resources, resulting in regional or national drawdown of resources that limit the capacity to fight fires in other regions, particularly when very large fires become the top national priority due to proximity to resources at risk or infrastructure. Very large fires also tend to require much more complex, multiagency management teams, fewer of which are available during the fire season. This complexity also can be associated with greater costs per unit area to fight the fire, since city and county agencies are often involved.
The U.S. Forest Service spent about $1.1 billion on fire suppression in 2014 and projects it will need to spend nearly $1.8 billion ten years from now.
NOAA adds there are important human health and environmental implications, which are difficult to put a price on: “The smoke created by these fires exacerbates chronic heart and lung diseases while also degrading visibility and altering snowmelt, precipitation patterns, water quality, and soil properties. In addition to public health impacts, projected trends in extreme fire events have important implications for terrestrial carbon emissions and ecosystems.”
Global greenhouse gas reductions could temper the projected feverish increase in fires and their economic toll. The EPA presents a scenario in which greenhouse emissions decline, which slows climate warming and reduces the amount of area burned by 13 to 14 percent compared to business-as-usual. It estimates more than $10 billion in avoided fire mitigation costs under this scenario.
The area burned by wildfires in the U.S. shows an increasing trend in recent years. Since the 1980s, 9 of the 10 years with most acres burned have occurred since 2000 according to National Interagency Fire Center data.
While the area burned shows an increasing trend, there is tremendous year-to-year variability owing largely to weather fluctuations. 2014, relatively speaking, was a quiet wildfire season.
2015 has been a particularly bad year for wildfires in the Pacific Northwest and Alaska, whose future was not explicitly analyzed in the NOAA or EPA analyses. However, experts project dramatic increases in the Last Frontier as well. The U.S. Global Change Research Program says the area burned is likely to double there by mid-century.