USA — No one in Colfax or Auburn will breathe a whit easier knowing this, but the heavy wildfire smoke that gave their towns a carbon black eye on the Air Quality Index on Monday is historically the norm for the foothills, studies show.
Analysis of tree rings and oral histories of American Indians and Euro-American surveyors suggests that the cobalt blue skies typifying the Sierra today were more the exception up through the 19th century.
The skies likely were smoky much of the summer and fall in the mountains and other remote and parched regions of California, where fires were largely ignored.
The Chumash Indian name for what is now the Los Angeles area translates to “the valley of smoke,” according to Gordon J. MacDonald, a geophysicist and professor formerly with the University of California, San Diego.
The chronic pall of dense smoke frustrated mapmakers. As C.H. Merriam, chief of the federal Division of Biological Survey, noted in 1898:
“Of the hundreds of persons who visit the Pacific slope in California every summer to see the mountains, few see more than the immediate foreground and a haze of smoke which even the strongest glass is unable to penetrate.”
Wildland firefighting didn’t occur until the turn of the 20th century, after the federal government set aside land as parks and created the Forest Service.
“Fire suppression became its reason for being,” Yosemite-based U.S. Geological Survey scientist Jan W. van Wagentdonk wrote of the Forest Service in an article last year for the journal Fire Ecology.
“It was the only policy for all federal land managers until the late 1960s when (National Park Service) officials recognized fire as a natural process.”
The amount of land burned in today’s far more urbanized and farmed California pales against the acreage consumed historically, before Euro-American settlements, according to University of California, Berkeley, environmental researchers.
The scientists estimated that an average 4.4 million acres burned annually in California before 1800, compared with an average 250,000 acres a year in the last five decades, 1950 through 2000.
That’s nearly as much land as wildfire consumed in the entire United States during a whole decade, 1994-2004, which fire officials deemed “extreme,” said the study, which was published last year in the journal Forest Ecology and Management.
“The idea that a U.S. wildfire area of approximately (4.4 million acres) annually is extreme is certainly a 20th or 21st century perspective,” the researchers concluded.
To calculate the extent of historic wildfires, scientists led by UC Berkeley’s Scott Stephens calculated the extent of pre-1800 fires from published data on fire rotation – the length of time necessary to burn an area.
They also determined fire frequency based on the years between fire scars on tree rings and the burning practices of American Indians, found in oral histories. The amounts of smoke particles emitted are overwhelming by today’s standards.
Looking at the estimated burned acreage, researchers found that wildfires spewed an average 1.3 million tons a year of tiny smoke particles in prehistoric California compared with about 78,000 tons in 2006, the most recent year for which the data in available.