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Wildfires, Weeds Hurt Desert Tortoise Habitat

Posted on: Monday, 26 February 2007, 06:00 CST

Wildfires fueled by invasive weeds in the Mojave Desert have taken a toll on federally protected desert tortoises, and scientists studying the problem need another year to gather data to chart the right course of action.

That was the buzz Friday among biologists gathered at Sam's Town for the 32nd annual meeting of the Desert Tortoise Council.

"The take-home message: It's a problem," said Lori Rose, a biologist for Washington County, Utah, who chaired a session on how wildfires in 2005 affected habitat of the threatened desert tortoise and other species.

More than 1 million acres of desert tortoise habitat burned in 2005 in the Mojave Desert region that spans southern parts of Nevada, Utah, California and Northern Arizona.

That included 32,000 acres of designated critical habitat for the desert tortoise just in Southern Nevada, said Kristina Drake, of the U.S. Geological Survey in Henderson.

Drake and colleagues Matt Brooks and Todd Esque said it will take at least another year to know some of the answers on how to best restore habitat and deal with the increasing problem of non-native cheat grass, red brome and Sahara mustard that serve as flash fuels for wildfires sparked by lightning strikes and other ignition sources on public lands.

"We need to have more information to know what's the prognosis is for desert tortoises," Esque, a research ecologist, said during a break in Friday's symposium.

"At one level, we have a great amount of concern. The direct impact of fire is loss of tortoises," he said. "We know we can lose large numbers. We're even more concerned abut the change of habitat."

Rose, citing a presentation by Brooks earlier in the day, said the expensive technique of reseeding charred areas with native plants that tortoises eat might not be the answer. The effort only leaves abut 140 to 200 seeds per square meter, compared to 6,000 seeds under normal conditions in the same size area.

About 80 percent of the seed bank in the soil dies in burned areas.

"Though none of us have been happy with the results ... those seeds are still out there," she said. "There's nothing to prove reseeding doesn't work, and we need to try it."

Rose noted the increased interest among scientists to treat burned areas with herbicides to reduce the dominance of non-native grasses.

A 10,000-acre plot of Zion National Park in southern Utah was treated with such a herbicide last fall.

"That's a big deal," she said, because the National Park Service has allowed it but the Bureau of Land Management doesn't have authority to do expansive treatment."

Biologists estimate there was a 40 percent to 50 percent mortality rate for desert tortoises in burned areas in southern Utah. Seventy-percent of those that survived preferred to relocate to unburned areas.

Ann McLuckie, a wildlife biologist for the state of Utah, said fires burned 25 percent of the habitat in Red Cliffs Desert Reserve, an area in southwestern Utah that was established in 1996 for desert tortoise habitat.

"What we're seeing is ecosystem conversion from desert vegetation to non-native grasses. It has a devastating impact on tortoises because their landscape is changing," McLuckie said.

In an effort to better monitor tortoise populations, the Desert Research Institute is fine-tuning the use of dogs to sniff out tortoises.

Now in its third season, the latest stage will focus on small tortoises in Southern California, said DRI researcher Mary Cablk.

"We treat the tortoises as if they are explosives," she said, comparing the tortoise dogs to bomb-sniffing dogs.

Four breeds are being used in the project: German shepherds, Labrador retrievers, border collies and Australian kelpies.

Source: Las Vegas Review - Journal

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