The size of wildfires burning across Arizona and the West has increased dramatically in recent decades.

But fires still burn only a fraction of the area they did before Europeans arrived, according to a study by researchers from Utah State University and elsewhere.

In the past several years, the amount of acreage burned in the West has jumped from 2 million or 3 million acres annually to perhaps 10 million acres.

Fighting those fires now consumes half the Forest Service budget.

Some 10,000 firefighters battle wildfires every summer, and 10 to 14 firefighters die each year, according to the Congressional Research Service. The number of structures burned rose from about 2,000 in 2014 to 12,000 in 2017.

Yet, before Europeans arrived, between 4 percent and 12 percent of the western United States burned every year, according to the study in Earth’s Future, published by the American Geophysical Union.

The number of acres burned would have to increase about tenfold from last year’s devastating 9 million acres to match that total.

The western states including California cover about 850 million acres, so 10 percent would be about to 85 million acres burned every year. The National Interagency Fire Center statistics show that up until about 1943, 30 million to 50 million acres burned every year. But, between about 1944 and 1956, the number of acres dropped to 6 million to 15 million, as the federal government built up a huge system to snuff out forest fires quickly.

The average number of acres burned dropped to between 3 million and 6 million from 1957 to 2003. The average then jumped to 6 million and 10 million except in wet years. In 2017, 10 million acres burned, with a similar total in 2018. The total number of fires didn’t change much, but the number of fires greater than 100,000 acres in size exploded.

Overall since 1970, the acreage burned by wildfires has risen 400 percent in the West, as the fire season has expanded.

Worse yet, the nature of the fires changed thanks to drought, an overgrown forest, and decades of building homes in the wildland-urban interface (WUI) — like Payson and Show Low.

The number of lives lost and the number of structures burned has increased. The economic damage due to wildfires in California in 2018 was estimated at $400 billion.

Ironically, the study authors concluded only a dramatic increase in low-intensity fires can restore healthy forests and contain the devastating megafires now besetting the West. Low intensity fires thin the forest, restore soils and mostly benefit wildlife.

Firefighters also have a chance to keep those low-intensity fires from consuming neighborhoods, while they have little chance against megafires like the one that consumed Paradise in California.

However, that means the Forest Service must clear buffer zones around forested communities, to help contain those much more frequent fires.

The Forest Service has cleared some 50,000 acres of buffer zones around Rim Country communities in the past 15 years.

The White Mountain Stewardship Program in the White Mountains has also cleared buffer zones around many communities there, including thinning projects that saved Springerville and Alpine from the Wallow Fire. Even with the buffer zones it will be difficult to return to a reliance on controlled burns with flammable, ill-prepared communities scattered throughout the forest.

That means towns like Payson and Show Low must adopt WUI building codes, to keep embers from a nearby fire from setting buildings on fire.

The rise in average temperatures and projections of longer, deeper droughts will make the problem worse, without the widespread use of managed fire, concluded the study authors.

“The annual amount of area burning can be informative for demonstrating that wildfires are on the rise with climate change, but alone, this metric is insufficient,” said Brendan Murphy, lead author of the study at Utah State University. “If we hope to better predict the future risks wildfires pose to water resources and more effectively manage our ecosystems, then it is critical we give other wildfire attributes — specifically burn severity — more consideration.”

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