Incendios Forestales del Oeste
Jul 26, 2017
Wildfires have burned more than 4.5 million acres in the U.S. so far in 2017. That’s 38% more than the average acreage burned for the year-to-date over the past decade. And it is the third largest area burned by wildfires in the last decade through late July.
The bulk of U.S. wildfires burn in the western half of the country because soils and vegetation are generally drier there in summer than in the East. As temperatures rise from the increase of greenhouse gases, evaporation rates from soils increase, which can worsen drought and dry out vegetation, creating ample fuel for fires. Hotter and drier conditions also allow wildfires to spread over large areas. Overall, the West is seeing trends toward more large wildfires burning more acres with longer fire seasons. In fact, the most active wildfire seasons are often those that are hotter and drier than average.
Wildfires can be very costly. Of the 17 years since 2000, the U.S. Forest Service has spent more than $1 billion in 12 of them to suppress fires, whereas in the last 15 years of the 1900s, the annual cost only exceeded $500 million dollars twice.
Large wildfires are currently burning across much of the West and the threat of damaging wildfires extends across parts of the Great Plains. The ongoing drought in North Dakota and eastern Montana will keep wildfire risk higher than average there through at least early fall. And despite the beneficial snow that fell last winter in California and Nevada, wildfire risk is also expected to be higher than normal in parts of those states leading into the fall, as additional vegetation blossoming from the wetter winter has increased the fuels available to burn.
Conditions that favor more wildfires are likely to become more common and widespread in the coming decades. In addition to rising temperatures contributing to worsening droughts, winter snowpack is also trending downward in the West. This further allows soils to dry out more quickly in the spring and summer, increasing wildfire risk.
Our analysis of data from the U.S. Forest Service included fires in the contiguous western U.S. in which at least 1,000 acres were burned. Prescribed burns and other management-related fires were excluded from this list. Data used for analysis were obtained from the U.S. Geological Survey, which has records that begin in 1980.
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