Environment

California wildfires will grow 77 percent as climate warms. Should forests be thinned?

You think this has been a bad summer for wildfires in California? Just wait a few decades.

The volume of acres that will be consumed by wildfires in an average year will soar 77 percent by the end of the century, according to a climate change study released Monday by state officials.

That would translate into roughly a half-million acres of additional wildfires in an average year — or the equivalent of two extra Carr Fires. Currently about 720,000 acres burn in an average year, according to Cal Fire, although the numbers have spiked in recent years, and so far in 2018, more than 810,000 acres have been consumed.

The state’s fourth Climate Change Assessment, released Monday, comes as California weathers one of its worst fire seasons ever — and the debate over fire management intensifies. On a recent visit to Carr Fire sites in Redding, Interior Secretary Ryan Zinke and Agriculture Secretary Sonny Perdue all but dismissed global warming as a factor in the fires and demanded that California’s forests be thinned through a combination of logging and prescribed burns.

Now the state Legislature is considering a pair of bills that would ease restrictions on logging larger trees on private lands as a means of reducing fire risk. The bills also would give landowners more leeway to build temporary roads in their forests to facilitate logging operations.

Environmental groups generally agree with forest thinning to reduce the presence of wildfire “fuels” but are lining up to oppose the bills, saying the logging of big trees actually would worsen fire hazards. “It weakens environmental laws to allow more logging of large, fire-resistant trees,” said Chad Hanson of the John Muir Project, an environmental advocacy group. “The larger the trees, the more fire resistant they are.”

But Rich Gordon of the California Forestry Association, which represents the timber industry, said limiting loggers to small trees makes forest thinning uneconomical. He said the legislation would allow slightly larger trees to be taken down — no more than 30 inches in diameter. “Certainly you don’t have to take out a lot of big trees,” he said.

The Climate Change Assessment is a suite of 57 reports covering the projected impacts from global warming on topics including agriculture, water supply and public health. The assessment, the first in six years, was released Monday by the California Natural Resources Agency, Energy Commission and Governor’s Office of Planning and Research.

In addition to growing wildfire risks, Californians will have to live with considerably hotter weather as global warming continues. Most climatologists believe average temperatures could rise by as much as 3.5 degrees by 2100. Inland areas, deprived of the cooling effects of the ocean, figure to suffer more. The report released Monday said average daily maximum temperatures in the Sacramento Valley will grow by 10 degrees by 2100. The average number of “extreme heat days” in midtown Sacramento, when temperatures hit 104 degrees or higher, will grow from four days a year to 40.

Already suffering from one of the worst seasons on record, California’s wildfire plight will worsen considerably as the years go by. LeRoy Westerling, a UC Merced climatologist who contributed to the Climate Change Assessment, said the main problem is that the few mega-fires that do most of the damage will simply become larger and do more harm.

“A small handful of really large (fire) events contributes most of the impact,” said Westerling, a fire-science expert, in an interview. “When you increase temperatures and make precipitation more variable, and all of the other effects we expect from climate change, you make those really extreme fires even more extreme.”

Westerling said the expected increase in fire acreage will vary considerably by region, with the heavily forested mountain areas taking the biggest hit.

“Places like the Sierra Nevada increase a lot more,” he said.

The increase in fire risk comes with a growing price tag. A companion report says homeowners can expect their residential insurance premiums to increase 18 percent by 2055 in the most fire-prone areas of Sierra Nevada foothills.

As it is, California is enjoying something of a temporary lull in the 2018 fire season. The worst dangers have passed from the Carr Fire, which was blamed for eight deaths, and the Mendocino Complex Fire, the largest fire in the state’s history. But the National Oceanic and Atmospheric Administration has said the rest of the fire season will be hotter and drier than usual, with the possibility of fierce winds fanning the flames.

The Climate Change Assessment said more aggressive management of California’s millions of forested acres would soften the impact of climate change on wildfire risk but not reverse it.

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