Invasive plants increase danger of desert fires

Tuesday, July 19, 2005 | 9:41 a.m.

The wildfires that have blazed through more than 933,000 acres of dried weeds and grasses in Southern Nevada since late June were fed by an alien invasion of fuel, experts say.

Grass and brush seeds from Europe and Asia that have been spreading since the 1890s have changed the desert landscape, said Lee Nelson, U.S. Fish and Wildlife Service fire management officer. After last winter's heavy rains, warm spring temperatures spurred explosive growth among non-native plants, especially those grasses, Nelson said.

The offenders include cheatgrass, red brome and Sahara mustard plants. Nevada's introduction to the Euroasian seeds arrived in the form of native seed contaminated with the foreign seed in the 1890s.

Cheatgrass continues to spread throughout northern and central Nevada, reaching into Utah, Idaho and Oregon, crowding out native plants, state forester Pete Anderson said.

But red brome is the big problem in the southern portion of the state because that variety likes it hot and thrives in Southern Nevada's deserts, Anderson said.

The desert in Nevada used to have plenty of bare ground, and that helped keep wildfires from becoming massive.

"There'd be a yucca plant or Joshua tree, then bare desert around it," Nelson said. Not this year after rains watered the seeds from weeds that have lain dormant since 1999, another epic fire year in Nevada when 1.8 million acres burned.

"This is unprecedented," Nelson said of this summer's fire activity.

Authorities imposed tighter fire restrictions at the Desert National Wildlife Refuge, northwest of Las Vegas, earlier this month because of explosive growth of invasive grasses that could fuel more wildland fires, Nelson said.

Fire officials are worried about the rest of the summer after thunderstorms produced dry lightning that sparked wildland fires starting June 22.

The National Weather Service is predicting a drier-that-normal Southwest monsoon season this year, continuing the drying trend among non-native grasses.

"There's a definite fire danger if, and only if, we get dry thunderstorms," Weather Service meteorologist Brian Fuis said.

Richard Modee, coordinator for weed management at the state Department of Agriculture, said the current condition of the desert is "awful."

While Modee is working with Clark County and federal agencies to develop a plan to manage Eurasian weeds, this year the people working with him are in the field fighting fires or studying the growth, he said.

A former firefighter in the Angeles National Forest north Los Angeles, Modee said that flames in recent fires moved at 7 mph through the dry, brown brush.

"That's unheard of," he said.

While fires are necessary for forests to renew themselves, wildfires have scorched the desert for a only few decades.

Craig Dremann, an ecologist and co-owner of the Redwood City Seed Company in Redwood City, Calif., said vehicles, people and livestock spread the seeds of a weed known as schismus.

"This Middle Eastern weed may ultimately do more property damage in the Southwest than any terrorist," Dremann said.

One to two tons of dried grass per acre have fueled the wildfires that have burned throughout Southern Nevada this year, experts say.

Since the 1970s, desert areas below 3,000 feet in elevation have been invaded by nonnative grasses filling in bare spots in the desert and contributing to the spread of wildfires.

The first invasive weeds to cause fires in the Southwest's deserts were red brome and cheatgrass, said Mark Dimmitt, director of natural history with the Arizona-Sonora Desert Museum.

Two new invaders have added to the problem. Buffelgrass grows in the wettest part of the Sonoran Desert above roughly 2,000 feet and came to the West in livestock feed.

Sahara mustard blooms in low desert valleys, Dimmitt said of the weed that sprouted all over the Las Vegas Valley in backyards after heavy winter rains.

Once these invaders grow rapidly during heavy rains, they dry out in hot summer months and create an ignition switch to burn desert scapes.

Many of the seeds ride the winds, helping to distribute them. Seeds are also picked up on tires, truck beds or the swirls created when cars zoom along highways in the desert.

"We wash our trucks inside and out before and after we go to a fire, to remove foreign seeds," Anderson said.

"These weeds can convert huge areas of our deserts into weedy wastelands," Dimmitt said.

"Fires below 3,000 feet (elevation) are a very recent phenomenon and are completely unnatural," Dimmitt said.