INVASIVE PLANTS, ANIMALS A HAZARD NATIVE HABITATS FOUND TO BE IN TROUBLE.

Byline: Susan Abram Staff Writer

SANTA CLARITA - Down the Santa Clara River, dozens of invasive species have crept in, squeezing out the natives.

The brown-headed cowbird lays its eggs in the nests of other birds.

Stalks of arundo and sweet-smelling eucalyptus trees choke out the cottonwoods. And the African clawfooted frog swallows almost anything in front of it, even other frogs.

It's a cycle that has nature experts squirming, but also defiant in their decision: eradicating what doesn't belong to save what does.

An example can be seen at Piru Creek, where the California Department of Water Resources is considering stopping the flow of water into the creek from Pyramid Lake. It's an effort to protect the native and federally endangered arroyo toad from the aggressive bullfrog, a non-native that thrives in full riverbeds.

Invasive species threaten California native species by thriving in their habitats and competing for limited resources, according to the Nature Conservancy.

The group says California is among the hardest hit of the 50 states, with 674 plant and animal invaders now naturalized within its borders. Invasive species represent the top threat to biodiversity, agriculture, fishing and recreation in the state, costing California hundreds of millions of dollars annually, according to the Nature Conservancy.

Local biologists say the Santa Clara River, known as one of the last natural waterways in California, is also under attack.

For an ecosystem to thrive, it must remain diverse, they add.

``Locally, arundo is a bamboo-like grass that's highly invasive because it chokes up the river and crowds out the native species like willows and cottonwoods,'' said Ian Swift, biologist at the Placerita Nature Center.

Arundo can grow up to 20 feet high. Though it was introduced into this country centuries ago as an ornamental vegetation, it has become a pest, soaking up water like a sponge and choking other vegetation out as it grows.

As for birds, the European starling and the brown-headed cowbird are both nest parasites, Swift said.

The cowbird is native to the United States, but its range has expanded, he said.

``It goes around and finds the nest of other birds and lays its eggs in other nests,'' Swift explained. ``Sometimes, their young hatch earlier, and the hatchling pushes everything else out of the nest. Then the other parent is stuck raising this large cowbird.''

Recently, there has also been more invasive fungus found in the Santa Clara River, thanks to the African clawed frog.

The African clawed frog was released locally in the 1950s after it was used in laboratories for experiments on drugs, such as birth control. Fungus found on the frog may be responsible for spreading and contributing to the decline of amphibians in the river, Swift said.

Biologists say much can be done to stop the spread of invasive species locally.

``With a little bit of management, the Santa Clara River could be a riparian area,'' said Los Angeles County Natural Areas Administrator Frank Hovore.

In October, the U.S. Forest Service pledged $100,000 to Los Angeles County to continue a long-term effort to rid the tributaries of the Santa Clara River of arundo.

But more can be done by residents to help preserve the native species of the river, Swift said.

``One of the things you can do is not encourage invasive species in your own back yard,'' he said. ``The eucalyptus tree is not a native. It's invasive, and it's doing the same as the arundo is doing. If people are interested in planting trees, they should try the oak, the cottonwood, or the willow trees.''

Susan Abram, [phone]

susan.abram(at)dailynews.com