Invasion of Foreign Flora Weeds Out Native Species in California

In a new park along the Central California coast, volunteer Dave Sands hacks at a eucalyptus sapling with his machete. Then he chops away at a yellow-flowered French broom.

He points disgustedly at German ivy smothering a seasonal stream bed, and at stands of pampas grass overrunning a wide bend in the trail.

Finally he smiles, pointing up 30 feet on a hillside.

“Monkey plant,” he says. “Now that’s native.”

The monkey plant and occasional mulberry bush in El Granada Quarry Park near Half Moon Bay are rare native survivors in a sea of exotic plants imported from the Mediterranean, India, Australia and elsewhere.

Free from natural enemies, this army of plant invaders is robbing California of its biological heritage, squeezing out native species that cannot compete with the fast-growing foreigners.

Vanishing along with those plants are native animals such as deer, raccoon, fox, coyote and many species of fish dependent on the state’s natural ecosystem.

“This mixing of plants is a major biological upheaval, of greater consequence for us than the ozone hole, than global warming,” says Jim Trumbly, a senior ecologist for the state Department of Parks.

Jacob Sigg, chairman of the invasive plants committee for the California Native Plant Society, says at least 600 foreign plants have reached California by accident or design.

The damage is extensive.

Virtually no native grasslands remain in California, Trumbly says. Foreign grasses, eucalyptus trees, French broom and other invaders have seized the state’s open spaces.

In parched Southern California, Mike Kelly, state secretary of the California Exotic Pest Plant Council, says the encroaching plant pests seem intent on sucking up what little water remains.

A bamboo-like plant called giant reed has taken over riverbanks and stream beds, sending down deep taproots to siphon off the water while choking waterways to crowd out native willow, cottonwood and sycamore trees.

“It’s a monoculture of this one plant marching down the streams,” Kelly says.

Along the Santa Ana River in Riverside County, 30 public and private agencies joined last year to cut and kill enough giant reed to dry up the water supply for 100,000 people.

In the desert areas, tamarisk swallows up water holes, its deep roots drying up pools vital to the survival of plants and animals alike.

Los Angeles is battling ficus trees imported from India for their ornamental value and fast growth, but whose octopus-like roots now break pipes, sidewalks and streets.

On Angel Island in San Francisco Bay, state rangers supervise the removal of 10,000 eucalyptus trees that have overgrown parts of the scenic refuge. That logging operation ran into opposition from citizens in the late 1980s, until the Oakland Hills fire muted public enthusiasm for the trees.

“The aesthetics of this island were dramatically changed by eucalyptus. It’s not a natural look,” state ecologist Dave Boyd says. “And they are terribly dangerous--this stuff is highly flammable.”

California is so overrun--and the solutions so expensive--that the Parks Department makes no systemwide effort to eliminate the exotics.

The best they can do for now, Trumbly says, is pick a few spots to protect the dwindling remains of California’s original ecosystem.

“Problems with exotic species have clearly overrun our ability to deal with them,” agrees Jay Watson, Western regional director of the Wilderness Society.

There are some efforts to at least check, if not reverse, the invasion.

Boyd is experimenting with controlled burns on Mt. Tamalpais north of San Francisco to wipe out the French broom that plagues its slopes. The results are promising, but controlled burns are risky near developed areas.

The San Diego city park system aggressively roots out exotics.

In various Golden Gate National Recreation Area sites around San Francisco, weekend volunteers laboriously pull up German ivy, ice plant and other nonnative species.

At least one private company has found a way to make money and create jobs while fighting eucalyptus. Planned Sierra Resources has a contract to remove the Angel Island trees, and coordinates with organizations such as California ReLeaf to plant native species in their place.

Fred Gibson, Planned Sierra’s marketing manager, says that in most cases the company removes the trees at no charge--a boon to strapped public agencies and homeowners--making its profits by selling the eucalyptus to Japanese paper makers.

“We employ people, we recycle the fiber, it provides export income, and it mitigates a lot of hazards,” Gibson says. “It’s a win-win situation.”

But although volunteers, burning and logging can help, most ecologists believe that the only long-term solution is nature itself.

Eventually, they say, the quirks of California’s climate will catch up with unprepared exotic plants, or natural enemies will follow them from their homeland.

But mankind seems less than eager for the natural balance to be restored.

A case in point is the Tasmanian blue gum eucalyptus tree, brought to California after the Gold Rush and initially planted for shade and windbreaks. At the beginning of the 20th century, entrepreneurs planted large stands of eucalyptus for timber, but abandoned them when the wood proved unsuitable for lumber.

The trees spread unchecked until 1984, when an inch-long beetle called the eucalyptus long-horned borer reached Southern California from Australia, gradually spreading northward. In recent months, both Stanford University and Mills College have reported serious borer infestations.

But what should be good news for the environment is bad news for human residents who use the trees for shade--or don’t want dead eucalyptus within falling or burning distance of their homes.

Instead of letting nature take its course, homeowners in San Diego imported an Australian wasp that preys on the borers. Mills and Stanford are looking at the same solution.

The approach preserves shade and peace of mind, but at a cost to California’s ecology.

“I often wonder if nature won’t take care of this in the long run,” says Sigg of the Native Plant Society. “But people live in the short run.”