Tuesday, July 18, 2006 | 7:28 a.m.
The smoke choking Southern Nevada from huge California wildfires is a harbinger of things to come, scientists are warning, just one more effect from an onslaught of global warming.
Scientists at the Scripps Institution of Oceanography at the University of California, San Diego, and the University of Arizona, have found that the frequency and intensity of wildfires in the West are growing as the climate gets hotter. The research, presented in the American Academy for the Advancement of Science's monthly journal Science, found that seven times more forested land burned in the w estern United States between 1987 and 2003 than the prior 17 years.
The researchers found that fires came more frequently and burned hotter, and the fire season lasted longer than the historical average. The effect is another indication from scientists that climate change is not just a hypothetical issue for the future, but is happening now, particularly in the West.
David Mouat, an associate professor in Ecosystem Sciences at the Desert Research Institute in Reno, is studying Western climate changes independently, and believes the new wildfire research is consistent with what he has seen.
"I've been thinking about it a lot, and the more I think about it, the more sense it makes," Mouat says. Earlier springs, higher temperatures, less precipitation and more precipitation falling as rain instead of snow are all consistent with more wildfires.
"Those consequences are pretty intense," he says, but they aren't alone. Along with the climate changes have come invasive species that literally add fuel to the fire - grasses such as red brome and cheat, and the shrublike tree called tamarisk or salt cedar.
"That means we have fuel that is ready to burn much earlier. If you have very dry fuels in the form of invasive species and you have fire weather, they can combine to make catastrophic fires."
Most climatologists believe human use of fossil fuels, which put "greenhouse gas" carbon into the atmosphere, is warming the planet. A few vocal opponents disagree.
The scientific community, including the American Meteorological Society and the National Academies of Science, however, believes that global warming is a real and growing problem.
In the West, researchers have found an average temperature rise of 1.6 degrees Fahrenheit over the last few decades. The federal Intergovernmental Panel on Climate Change recently released projections of temperature increases of 3 to 9 degrees by 2069 in the West, while precipitation in the same area could drop by 15 percent. Officials with water agencies such as the Southern Nevada Water Authority are working to diversify their water sources as drought continues to threaten the Rocky Mountain snow pack feeding the Colorado River, source of Las Vegas' drinking water.
According to the National Fire Information Center, more than 64,000 fires have scorched 4.3 million acres in the West this year. The first seven months produced more fires and burned more acres than any similar period in at least seven years and is eclipsing last year's number. In 2005 more acres burned - 8.7 million - than any since 1960, which is when the National Interagency Fire Center's Web site begins its data.
The federal response to the growing number and intensity of wildfires, especially in the West, has been the institution of the "Healthy Forests" plan to clean out dead and dying trees in the vast federal forests.
Chris Faehling, Nevada Division of Forestry fire protection officer for Clark, Lincoln, Nye and Esmerelda counties, says global warming could play a role in encouraging large forest fires, but other factors provide a more immediate threat.
"In my opinion, in regard to fire management, it's more of a forest health issue, especially in the West," he says. "Our forests in the West need help."
Drought has led to insect and disease outbreaks, while overcrowding of Nevada's pinion and juniper forests also stress the trees. Together, the conditions make forests in Nevada and the West ripe for burning.
A recent effort to reduce the fuels provided by overgrown vegetation in Lincoln County helped the forest health and encouraged native ground cover to come back, among other positive benefits, Faehling says.
Thomas Swetnam, University of Arizona professor and director of the Laboratory of Tree-Ring Research, says that even with the other factors such as drought and forest fuels are taken into account, climate appears to be having an effect on western wildfires. He says the data collected by him and two Scripps Institution researchers show a "clear correlation" between fires and higher temperatures over the western United States.
The higher temperatures and wildfires also are linked to the earlier arrival of spring, Swetnam says. According to the research, large wildfire activity increased "suddenly and dramatically" in the 1980s with longer wildfire seasons. It is climate change, not forest fuel accumulation, that is the primary driver in the change, the researchers have found.
The researchers looked at 1,166 wildfires of at least 1,000 acres that occurred between 1970 and 2003 on U.S. Forest Service and National Park Service land. They compared the fire data to climate data that included snowmelts, the arrival of spring and summer temperatures, flows of streams and ground moisture data for 240 sites in the West.
The increase in wildfire frequency and size ramped up around 1987, they say.
Swetnam says the research shows "one of the first big indicators of climate change impacts in the continental United States Lots of people think climate change and ecological responses are 50 to 100 years away. But it's not 50 to 100 years away - it's happening now in forest ecosystems through fire."
Those looking for more evidence of climate change can just walk outside. The average January-June temperature for the continental United States was the highest since formal record keeping started in 1895, according to a National Oceanic and Atmospheric Administration report last week. Drought continues to grip much of the nation, including the West.
Globally, last month was the second warmest June on record, and 2006 has been the sixth-warmest year to date.
The bad news for the climate is even worse when one considers the cumulative effect of forest fires, Swetnam says. One is that vegetation that once absorbed carbon is as it burns putting it back into the atmosphere - a "positive feedback" that could ultimately lead to even greater global warming.
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