Forest Thinning Can Prevent Fires, Save Water, Study Finds

Posted: May 14, 2018

Source: Courthouse News Service

(CN) – Better forest management would not only prevent wildfires but could serve as a valuable water-conservation tool, according to a study publishedTuesday.

California could save billions of gallons annually by undertaking significant forest-thinning operations, according to scientists affiliated with the National Science Foundation and the Sierra Critical Zone Observatory.

“We’ve known for some time that managed forest fires are the only way to restore the majority of overstocked western forests and reduce the risk of catastrophic fires,” James Roche, a National Park Service hydrologist and lead author of the new study, said in a statement. “We can now add the potential benefit of increased water yield from these watersheds.”

Indeed, a variety of scientific studies published in the last decade argue fire-suppression efforts in California have had a detrimental impact. The typical argument says that fire occurred naturally for centuries, allowing the forest to thin itself out and provide periods of regeneration. With fewer fires, tree density has grown. Now, when fires do occur, they burn with an unnatural intensity that creates ecological and economic disasters.

Last year’s Thomas Fire was the largest by acreage in California’s history, while the spate of wildfires that ravaged Northern California last fall was the most economically disastrous.

Tuesday’s study says thinning projects could also help conserve water, as trees require an enormous amount of water to carry out basic biological functions.

“By reducing the water used by plants, more rainfall flows into rivers and accumulates in groundwater,” said Richard Yuretich of the National Science Foundation.

Along with sucking up water the ecosystem could otherwise allocate to groundwater, river and reservoir replenishment, trees also undergo a process scientists call evapotranspiration.

Evapotranspiration is basically how trees “sweat,” as they emit water through tiny pores in their leaves.

According to the study, excessive evapotranspiration could interact with climate change to harm an already fragile California ecosystem reeling from years of prolonged drought with the prospect of more bouts of extreme weather.

The study, published in the scientific journal Ecohydrology, looked at observation towers in the Sierra Nevada Mountains and United States Geological Survey databases and found more water conserved in areas where forests had been thinned for fire management.

For example, Kings River Basin saved 3.7 billion gallons of water per year during an 18-year period beginning in 1990, the study said. Similarly, the American River Basin experienced a savings of 17 billion gallons per year over the same period due to similar thinning practices.

But achieving this type of significant, widespread forest restoration throughout the entire Sierra would require enormous spending.

The U.S. Forest Service says about 6 to 8 million of the 21 million acres of forest land it manages need immediate restoration, according to the study. Nationwide, 58 million acres are in need of immediate work.

For California alone, that work carries a price tag that could rise as high as $10 billion.

But the study authors hope the projects they espouse bring enough economic benefits to pay for themselves.

“Downstream users who benefit from the increased water yield are an important potential revenue stream that can help offset some of the costs of restoration,” University of California Merced scientist Roger Bales, a study co-author, said.