How climate change leads to more and larger wildfires in Arizona - The Arizona Republic

How climate change leads to more and larger wildfires in Arizona

Arizona wildfires are growing larger and more frequent. What role does climate change play?
Jake Frederico

Fire is a fundamental natural process across the Western U.S., one that serves an important ecological purpose. But climate change has significantly altered the wildfire season, experts say, and is leading to larger and more frequent fires.

Multiple studies have concluded that climate change has already led to an increase in wildfire season length, fire frequency and the size of burned areas. The wildfire season is longer in many areas due to factors such as warmer spring seasons, longer summer dry seasons, and drier soils and vegetation.

“If you’re concerned about wildfires then you need to be concerned about climate change and take it seriously,” said Don Falk, a professor in the University of Arizona School of Natural Resources and the Environment. He researches fire history, fire ecology and ecological restoration and resilience in a changing world. “If you’re concerned that we're having giant wildfires then you should be concerned about the things that cause those, and overwhelmingly the biggest driver of that is climate change itself.”

Forest fires in the western U.S. have been growing in size and frequency for several decades. In 2020, wildfires in the U.S. burned more than 10 million acres from July to December and killed at least 47 people. In Arizona, 978,519 acres burned, the largest number since 2011.

“There is no scientific dispute about the factors that are causing wildfires to get bigger,” Falk said. “There is no fundamental scientific disagreement that the increase in concentrations of greenhouse gasses coming from human activities is causing the earth to become warmer.”

In California, an eightfold increase in burned forested area over the last 50 years is tightly linked to increased atmospheric aridity. Across the West, the effects of climate change accounted for 45% of the total burned area from 1984 to 2015, according to research published in Advancing Earth Space Science.

More: Forests often regenerate after wildfires. Why the climate crisis could change that

What are the factors behind wildfire activity?

Experts say climate change is contributing to drier conditions and increasing fuel load, which likely is increasing fire frequency and magnitude. So when a lightning strike or a human activity causes a fire, the blaze has the potential to become much more intense and fast-moving.

The influence of climate change does not minimize non-climatic factors for forest fires. Drivers of forest fires can depend on multiple factors like location and change over time. Humans directly or indirectly start over 95% of the fires that threaten homes, and decades of increased development in fire-prone landscapes are leading to more fire disasters.

In 2020, a majority of burned areas in California, Arizona and the pacific Northwest were from human-related ignitions, according to research conducted on Pacific climate impacts by the University of Victoria.

And while fires have always occurred in the balance of nature, there is evidence that points to more large wildfires occurring than ever before.

“People will say, 'Oh yeah that’s always happened,' and it hasn’t always happened,” Faulk said. “There is nothing about the contemporary fire situation that has any analog in the past and that’s because of the way we have changed earth’s climate.”

How do hotter temperatures lead to more wildfires?

Since 1970, more large fires and more acres have burned as the West dries and heats up.

Spring and summer — both key seasons for wildfire — have warmed and grown longer across the West. Just this year, research from the USA National Phenology Center revealed that Tucson has warmed 6.1 degrees Fahrenheit since 1970. Across the nation, Reno saw the largest spike in temperatures, increasing more than 7 degrees over the last 40 years.

Hotter temperatures evaporate more moisture from soil and vegetation and dry out trees, shrubs and grasses. This turns leaf litter and branches into perfect kindling for fire to tear through.

Snowpacks are also shrinking and melting earlier, leading to a longer period of dry conditions in areas already prone to wildfires. This is also making forests more flammable by reducing water availability for vegetation.

Projected increases in fuel aridity could mean that trends will continue on an upward slope and that fires will become bigger and potentially deadlier.

Are there any solutions?

Experts agree that to effectively minimize the negative human impacts of wildfire, it is essential to address the root issues that are driving climate change. Falk said he is optimistic that people can address the issues causing climate change to prevent more large-scale and devastating fires in the future.

“It’s still within our power to turn that around,” Falk said. “But we have to take it seriously and stop arguing."

He compares the devastating effects of climate change, and the political debates that surround it, as a speeding locomotive with no brakes.

“A train coming down the tracks, (people) want to argue whether that whistle is a quarter of a mile away or 10 miles away," Faulk said "You should turn around and look at it, and then you’ll know exactly where you are.”

Jake Frederico covers environmental issues for The Arizona Republic and azcentral. Send tips or questions to jake.frederico@arizonarepublic.com.

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