Scientist leans toward burning in Sierra, not mechanical thinning

Posted by Mark Grossi on February 11, 2014 

Thinning the forest would help avoid big blazes such as the Rim fire near Yosemite.

U.S. FOREST SERVICE — U.S. Forest Service

"You cannot thin your way out of this."

That was the quote I couldn't fit into my Sunday story about the historic drought and the weaknesses it is exposing in the magnificent Sierra Nevada.

The quote from a scientist was about cleaning up the unhealthy, overgrown forests. I bring it up now because on reader suggested the Sunday story leaned toward logging or mechanical thinning. 

Actually, scientists have been going another direction for some time -- toward prescribed burns and letting natural, lightning-caused fires burn.

The scientist is Malcolm North, research scientist for the U.S. Forest Service and forest ecology professor at University of California at Davis. He is among the many experts I have interviewed on this subject over the last 15 years. 

Scientists have long said fire is a healthy, natural part of the Sierra's forests, contrary to the "snuff every fire" approach that was used many decades ago. Frequent, low-intensity fire burned clean up overgrown forests.

Thick forests are consuming more water than they did in the past and setting up the forest for catastrophic blazes like the Rim fire last year.

North said mechanical thinning has no hope of catching up with the overgrowth. The mountain range covers nearly 25 million acres -- an area larger than Maine. Many parts are inaccessible or forbidden for mechanical thinning.

Authorities are trying to clean up the Sierra, using a combination of mechanical thinning and prescribed burning each year. But the efforts do not amount to a tenth of what natural fire did in the past.

Forests are just getting thicker every year, North said, adding that the use of more fire should be explored.

There are criticisms of fire. Nearby communities can get smoked out if conditions are not right. And what if a fire gets away and causes damage?

North said the catastrophic fire danger must be addressed.

"The forest will burn eventually," he said. "You can say it's an act of nature, but we've made decisions that help keep the forest in this condition."

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