U.S. wildfires plummeted in 2019. Experts say it won’t last

18 March 2020

Published by https://www.sciencemag.org

USA –  Wildfire destruction last year was at its lowest level in the U.S. since 2004, ending several years marked by conflagrations that killed scores of people and caused billions of dollars in damage.

The number of acres burned in 2019 was low nationwide, including in California, where the threat of wildfire prompted utilities to cut off power to millions of people in October and November.

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Wildfires burned 890,000 hectares (2.2 million acres) last year in the mainland U.S., a sharp drop from the previous two years when wildfires burned an average of 3.6 million hectares (8.9 million acres) in the lower 48 states and killed 147 people in California alone.

The previous low for the continental U.S., recorded in 2004, was 607,000 hectares (1.5 million acres), according to the federally sponsored National Interagency Fire Center, which tracks significant wildfires.

Alaska was an exception to the trend. Wildfires burned nearly 1 million hectares (2.5 million acres) last year as the state suffered record heat. Alaska traditionally has the most wildfires in the U.S., although the damage often occurs in remote areas and does not threaten communities.

Climate change has extended the wildfire season and intensified blazes as higher temperatures have left vegetation drier for longer periods, according to the 2018 National Climate Assessment and other studies. The recent devastation from wildfires in Australia has been attributed in part to climate change, which researchers said helped produce the extreme heat that blanketed parts of the nation and made the wildfires more likely to have occurred.

The U.S. trend in 2019 does not change long-term patterns, experts said, and likely resulted from anomalies such as heavy precipitation that left forests and grasslands wetter than normal.

“We don’t think we will continue to see years like 2019. We’re already assessing 2020. So far weather patterns are lining up to culminate in above-average fire activity this year,” said Jessica Gardetto of the fire center.

Fire center data shows significant growth in the number of acres burned in recent decades, although Gardetto said the growing numbers may be a function of improved technology that measures the size of wildfires more accurately.

Wildfires burned an average of 1.3 million hectares (3.3 million acres) a year in the 1990s, according to an E&E News analysis of fire center data. The average more than doubled in the 2000s to 2.8 million hectares (6.9 million acres) a year. It maintained that pace from 2010 through 2019, at 2.75 million hectares (6.8 million acres) annually.

The fire center counts only wildfires that burn at least 40 hectares (100 acres) of forest or 120 hectares (300 acres) of rangeland.

In the western U.S., where roughly 90% of wildfires occur, the season has expanded “as a result of increased temperatures and earlier snowmelt,” according to the National Climate Assessment. Drier climates and reduced summer precipitation “have deepened summer droughts in the West and thus increased wildfire risk.”

As extensive precipitation fell on the western U.S. last spring, fire officials initially feared that would exacerbate wildfires by causing grasslands and forests to grow thicker than usual. But some of the vegetation remained wet through the wildfire season in October, Gardetto said.

“We had quite a bit of precipitation across the West last winter. That transitioned into a lot of precipitation in the spring that continued into May and June in some states. That prolonged the drying of vegetation which prolonged wildfire activity,” Gardetto said.

Research scientist Brandon Collins of the Center for Fire Research and Outreach at the University of California, Berkeley, said the U.S. avoided three- to five-day heat waves last summer that can trigger wildfires.

“You’re going to have up years and down years with wildfires,” Collins said. “Sometimes I think it’s just luck.”

The wildfire trend in 2019 is just one data point, Collins said. “You can’t entirely discount it. But I wouldn’t suggest it’s anything that reverses the thinking” about wildfires and climate change.

In California, which was devastated by wildfires that burned more than 1.4 million hectares (3.5 million acres) in 2017 and 2018 combined, firefighters were credited with containing blazes last year during the state’s notorious fire season. The state’s major utilities also took aggressive action, turning off power in hot spots to prevent transmission wires from igniting wildfires if heavy winds knocked them to the ground.

Wildfires in California burned 260,000 acres last year and killed three people, according to the California Department of Forestry and Fire Protection.

California’s wildfires burned an average of just 12 hectares (32 acres), E&E News’ analysis of national fire center data shows. The average in 2018 was 91 hectares (226 acres).

California utilities, most notably San Francisco-based Pacific Gas and Electric Co., faced major criticism for the blackouts, which lasted days in some cases and affected customers more than 100 miles away from an actual wildfire.

Collins said the blackouts occurred at “pretty appropriate times.”

Reprinted from Climatewire with permission from E&E News. Copyright 2020. E&E provides essential news for energy and environment professionals at www.eenews.net

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