forest fires

Forest thinning needed to save water

Dense forests suck up surface and groundwater and dump it into the atmosphere through the process of evapotranspiration. This means that there is less water for other uses.

“There are too many trees in Sierra Nevada forests, say scientists affiliated with the National Science Foundation (NSF) Southern Sierra Critical Zone Observatory (CZO).”

A new study supported by the National Science Foundation published in the journal Ecohydrology (see press release) proclaims “Billions of gallons of water saved by thinning forests.” The study of the Sierra Nevada Mountains in California notes that “excessive evapotranspiration may harm a fragile California water system, especially during prolonged, warm droughts.”

The primary methods of good forest thinning are fire and logging.

Forest Service policy exacerbated sound forest management. Remember Smokey the Bear, “only you can prevent forest fires?” But fire is nature’s way of managing forests. Logging was largely reduced for misguided environmental reasons such as saving the spotted owl.

From the NSF study:

“Forest wildfires are often considered disasters,” said Richard Yuretich, director of NSF’s CZO program, which funded the research. “But fire is part of healthy forest ecosystems. By thinning out trees, fires can reduce water stress in forests and ease water shortages during droughts. And by reducing the water used by plants, more rainfall flows into rivers and accumulates in groundwater.”

Using data from CZO measurement towers and U.S. Geological Survey satellites, researchers found that over the period 1990 to 2008, fire-thinned forests saved 3.7 billion gallons of water annually in California’s Kings River Basin and …17 billion gallons of water annually in the American River Basin — water that would otherwise have been lost through evapotranspiration.

Forest thinning has increased in recent decades in an effort to stave off disastrous wildfires fueled by dense forests. This study shows that restoring forests through mechanical thinning or wildfire can also save California billions of gallons of water each year.

Perhaps we should take guidance from the first land managers in North America, the Indians. In my article “The Pristine Myth” I note the following:

Archaeological and anthropological research during the last 25 years or so, shows that much of what we thought was pristine in the Western Hemisphere, even the Amazon rain forest, is actually human-formed landscape created by the first New World inhabitants, the Indians. It seems that American Indians, from North America, Mexico and South America, were the ultimate land managers, and they transformed the land to suit their needs. They constructed the world’s largest gardens.

American Indians built cities and civilizations, cultivated forests and farms, and developed more than half of the crops grown worldwide today. Indians, rather than subsist passively on what wild nature provided, instead survived by cleverly exploiting their environment. Their principal tool was fire. They did not domesticate animals for meat, but instead used fire to change whole ecosystems to raise deer, elk, and bison.

Related story:

Forest thinning may increase runoff and supplement our water supply

A new study (“Effects of Climate Variability and Accelerated Forest Thinning on Watershed-Scale Runoff in Southwestern USA Ponderosa Pine Forests” published October 22, 2014) conducted by The Nature Conservancy and Northern Arizona University recommends accelerated forest thinning by mechanical means and controlled burns in central and northern Arizona forests. The study estimates that such thinning will increase runoff by about 20 percent, add to our water supply, and make forests more resilient.

North American wildfires and global warming

Almost every time we have a major wildfire, alarmists blame global warming and claim that such warming will increase the incidence of wildfires. They also often claim that the number of wildfires is increasing. Their argument seems logical at first, higher temperatures and less precipitation will dry out forests making them more susceptible to wildfire.

The graph below compiled by C3Headlines using data from the National Interagency Fire Center in the U.S. and the National Forestry Database in Canada shows that the number of wildfires has decreased dramatically since 1970 and has remained relatively constant since the mid 1980s. The number of acres burned, however, has slightly increased and that may have to do with wildfire fighting decisions.


These numbers suggest some possible conclusions: either global warming does not have much influence on the number of wildfires, in contrast to alarmist claims, or there has not been sufficient warming since 1970 to test the hypothesis. Fire incidence could also reflect the time and severity of cyclic drought.

I’ve also included below the UAH lower tropospheric temperature record since 1979 when satellites began measuring global temperature.


Meanwhile, NASA says “Climate Models Project Increase in U.S. Wildfire Risk” The analysis was based on current fire trends and predicted greenhouse gas emissions. Time will tell if this is just another “garbage in, garbage out” computer simulation.

See also:

Mega-fires in Southwest due to forest mismanagement

Drought in the West

Droughts in the Southwest put in perspective

USDA says carbon dioxide can reverse effects of drought

Southwest Wildfire Hydrology & Hazard Workshop Proceedings

From April 3 to 5, approximately 70 people, representing various federal, state, and local agencies, researchers and practitioners, gathered at the University of Arizona’s Biosphere 2, north of Tucson for the 2012 Southwest Wildfire Hydrology and Hazards Workshop. The purpose of the workshop was to: 1) share the most recent research regarding post-fire hydrology and hazard assessments and mitigation and warning systems; and 2) discuss ideas for bridging funding gaps for research and warning system implementation.

Thirty papers presented at the workshop are available from the Arizona Geological Survey document repository here. The files consist mostly of power point presentations and PDFs. I recommend beginning with the first paper (50 pages) on the list (see here) which gives an overview of the proceedings.

Mega-fires in Southwest due to forest mismanagement

A new tree-ring and fire scar study from SMU and the University of Arizona finds that today’s mega-wild fires in the Southwest are unusual.

The 1,400-year record encompassed the Little Ice Age (1600 to mid 1800s A.D.) and the Medieval Warm Period (800-1300 A.D.) and found that fire incidence was nearly the same under both cool and warm, wet and dry conditions.

Forest policy of fire suppression prevented forests being naturally thinned by relatively small ground fires. The result was a build up of brush which exacerbated fires to produce even larger, more destructive wild fires. The researchers say, “The U.S. would not be experiencing massive large-canopy-killing crown fires today if human activities had not begun to suppress the low-severity surface fires that were so common more than a century ago.”

“This new study is based on a first-of-its-kind analysis that combined fire-scar records and tree-ring data for Ponderosa Pine forests in the southwest United States.”

“Fire scientists know that in ancient forests, frequent fires swept the forest floor, often sparked by lightning. Many of the fires were small, less than a few dozen acres. Other fires may have been quite large, covering tens of thousands of acres before being extinguished naturally. Fuel for the fires included grass, small trees, brush, bark, pine needles and fallen limbs on the ground.”

“The fires cleaned up the understory, kept it very open, and made it resilient to climate changes because even if there was a really severe drought, there weren’t the big explosive fires that burn through the canopy because there were no fuels to take it up there.”  “The trees had adapted to frequent surface fires, and adult trees didn’t die from massive fire events because the fires burned on the surface and not in the canopy.”

Read the entire press release from SMU here.

This study implies that attempts at “sustainable” forest management and endangered species issues have in fact made our forests more unsustainable.

See also:

Drought in the West
Droughts in the Southwest put in perspective

Forest fires create increased danger of destructive debris flows

Steep slopes denuded by forest fires are prime candidates for debris flows during our summer monsoon. A debris flow is a mixture of soil, cobbles, boulders, and water, with the consistency of concrete moving down a steep slope at 20 miles per hour or more. Typically debris flows are more destructive than floods.

In 2006, a particularly wet July spawned debris flows in the Catalina Mountains, the Chiricahua Mountains, and the Huachuca Mountains. Debris flows also occurred in 1977 and 1988 in the Huachuca Mountains. (See Arizona Geological Survey reports here and here.)

The Horshoe 2 fire in the Chiricahua Mountains has destroyed most of the vegetation in that range. We may have destructive debris flows this summer in the burned areas.