The tractor thrashes through a 40-foot-high wall of jungle, biting off hunks of tangled grasses and spitting them out onto the parched earth.
The work along the bone-dry San Jacinto River in western Riverside County is just one piece of the battle to eradicate a fast-growing invader known as Arundo donax. The giant cane is so thirsty that it is sucking the life out of Southern California waterways.
The world's largest member of the grass family, arundo can grow a foot a day. An acre of it swallows enough water to sustain 10 California households for a year.
"It's kind of unstoppable," said Kyle Washburn, who walked ahead of the tractor, hacking at the nearly impenetrable foliage with a machete to uncover abandoned cars or other large objects buried in it.
Worthy of a role in "Little Shop of Horrors," the oversized reed has taken over 20,000 acres of riverbed in three Southern California counties. Nearly every river in the Los Angeles Basin now has some giant cane, experts say, and it has been spotted as far north as Willamette, Ore., and as far east as New Or- leans.
The plant illustrates vividly how a nonnative species transplanted to new territory with no natural enemies can run amok. Cut it down, and new shoots spring up. Let it dry out, and it becomes a superb fire carrier.
Dense dry stands caught fire in the Santa Ana riverbed in a San Bernardino suburb last week, one of numerous river blazes regularly fueled by the cane.
During El Nino storms in the early 1990s, a mass of arundo that had been uprooted and washed downstream by flood waters piled up against a bridge between Corona and Norco. It lifted the bridge 18 inches off its struts, forcing it to close and preventing ambulances from reaching emergency rooms on the other side.
"The only thing I can compare it to is cancer. It spreads so fast, and it won't let anything else live in its midst," said Kerwin Russell, an environmental horticulturist with the Riverside Corona regional conservation district. Russell has spent nine years fighting giant cane, and says he will retire before the war is won.
Accounts of the plant's history and how it first arrived on American soil vary. A native of the Mediterranean and possibly parts of India, it has been around for at least 5,000 years.
The Bible mentions it and it is the likely source of the Pan's pipe of Greek myth, say researchers at the U.S. Department of Agriculture and UC Berkeley.
The cane, with its firm, straight structure, is still considered the best material available for clarinets and other reed instruments. However, efforts to harvest the plant commercially for musical instruments or paper have all failed in California, said Paul Frandsen, head of Riverside County's parks, who has been dubbed "Mr. Arundo" for his unflagging crusade to eliminate the plant.
Frandsen said Spanish settlers used it as a building material for California's missions.
But it wasn't until the federal government began planting arundo along riverbanks in the 1960s to control erosion that the cane began its rampant colonization.
"They had the right idea, but they put it near water," Russell said. "It loves water, and it has no natural enemies here.
"I suspected it was a drinker, and it is," said Frandsen, who commissioned a UC Riverside study in the early '90s that showed the plant consumes more than three times as much water as native plants.
The Santa Ana River has been hardest hit. The river runs 100 miles from the San Bernardino mountains through Riverside to Huntington Beach. At numerous points, the cane fills the river from bank to bank.
Arundo is so all-consuming that it has changed the ecology of much of the Santa Ana River, said Dick Zembal, a longtime biologist with the U.S. Fish and Wildlife Service who now is natural resources manager for the Orange County Water District.
Zembal explained that, for thousands of years, a multitude of creatures evolved in tune with the river's seasonal floods and dry spells. In just a few decades, arundo and other fire-resistant species have taken over, he said, replacing much of the river's plant and animal life.
While the stalks burn fiercely, the plant's massive underground root system allows it to re-sprout overnight.
"The roots act like a belly, or a gas tank--they store water and nutrients that the plant can just live off of, even in dry years," Russell said.
At least a dozen threatened or endangered songbirds, toads and other species that are unable to cope with fire have been pushed out.
Five water districts and an array of conservation districts--all members of "Team Arundo"--have gradually amassed nearly $25 million to root out the pernicious plant from the river.
An eradication campaign began in earnest in 1992 at the river's headwaters, and is moving slowly downstream. Crews work by hand with chain saws and buckets of pesticide, and sometimes with specially fitted tractors.