Region Being Invaded by Botanical Aliens

This is California as America knows it. Sun-dappled hills of golden grasses undulate into the distance, dotted with herbs and occasional wildflowers.

It is the kind of landscape made famous in old Western films, when the cowboys galloped their horses through the chaparral.

Now here’s the real story of this wild-land vista:

Most of the rippling gold grasses came from Spain, Italy, Greece, Morocco. That thick patch of pale green fennel is an insidious intruder from Southern Europe. The fabled tumbleweed, supposed icon of Western wildlife, is really an immigrant from Eurasia.

Hard to find is gray-green sage, with its soothing scent. Instead, wispy fennel exudes the sweetly pungent odor of licorice as alien plants squeeze out native scrub and chaparral.

“It’s definitely an invasion. It’s a very subtle one, that happens out of the limelight, and without people realizing it’s happening,” said Fred Roberts, 41, a U.S. Fish and Wildlife Service botanist who grew up a few miles from this valley in San Juan Capistrano and has watched acre after acre of native habitat overrun by opportunistic flora.

As benign and even lovely as they might seem, invasive plants are upsetting the balance of nature in California. They jump over garden walls to squeeze out native plants and threaten the endangered birds, butterflies and mammals that depend on those plants. They fuel desert wildfires, withering such beloved natives as the Joshua tree, and reshape dramatic coastal dunes.

Nearly one-fifth of the plants growing in California’s supposedly “natural” land today are considered exotic.

Just about all of us have had a hand in their arrival. Exotic flora have been intentionally planted on open lands by our federal government and our state transportation agency. They have escaped from our backyards or come piggyback in the goods we import from other states and nations.

The weeds are changing the very relationship between people and the state’s wilderness. Once, wild lands were places to be visited, safeguarded but otherwise left alone. Now they are increasingly like a giant garden where people pull out the weeds and replant native vegetation in a perpetual battle. In many cases, the problem has grown beyond the ability of park staff to contain it, and regular calls go out to the community for volunteer help.

America has been celebrated for its dramatic natural diversity, from cactus desert to mountain meadow to reedy marsh. But invasive plants are transforming the nation’s wild land into a more homogeneous weedscape.

Some biologists view this botanical invasion as a sort of chain-store takeover of nature. Just as Starbucks and the Gap have given a predictable sameness to the Main Streets of America, botanists foresee the day when the open land beyond the street will be decorated by somewhat similar expanses of opportunistic weeds.

“Even now, we’re looking at changed landscapes and are trying to grapple with how much that rate of change might accelerate over the next 100 years,” said federal biologist A. Gordon Brown, now on special assignment to Interior Secretary Bruce Babbitt to counter the invasion of newcomer plants and animals.

Plants are commuting across the globe to new homes, devastating the Florida Everglades and causing the free fall of hundreds of native plants and animals in Hawaii, where more than half of today’s wild species came from overseas.

Along the French and Italian rivieras, escaped aquarium algae is overtaking native aquatic plants. A South American water hyacinth is sweeping the African nation of Mali.

California is considered a particularly threatened region, in part because its generally mild climate--the same attribute that has made it a great place to cultivate everything from birds of paradise to daffodils--also serves as a mammoth petri dish for weeds from all over the world.

Newcomers planted imports like ice plant and beachgrass to stabilize the dunes, arundo donax to control erosion, bluegum eucalyptus for windbreaks, vincas to decorate gardens. These were quick to take root and make themselves at home.

Environmental groups have been slow to tackle the issue, in part because it lacks the dramatic immediacy of redwood lumbering or toxic dumps. People simply do not think of plants as aggressors. How can a wild plant be bad, especially pampas grass with its feathery fronds or the cheery yellow of wild mustard?

In fact, the first hurdle may be convincing the public to take the threat seriously, said Florida state ecologist Don Schmitz.

“You have a biologist like myself saying these plants are going to destroy the Everglades,” he said. “And people just look at you like you fell out of a tree.”

Endangered by Invasive Weeds

Botanists like Roberts know better. He can attest to how much the landscape has changed since he started collecting plants and studying botany at Dana Hills High School in Dana Point. He remembers rich expanses of native sages, buckwheat and chaparral. But continued home construction fragmented much of the wild land, making it vulnerable to weeds like artichoke thistle, with its sharp-edged leaves.

As a federal botanist, Roberts helped write the official listings for more than a dozen California plants now on the federal endangered species list, most propelled toward extinction in part by invasive weeds.

On ocean bluffs, along roadsides and inside office parks, Roberts points out dozens upon dozens of plants that aren’t supposed to be growing here.

Thick-leaved ice plant from South Africa turns the sides of freeways a luscious green but invades a San Pedro military depot that is the only known home of the Palos Verdes blue butterfly. Arundo donax, tropical-looking reeds, brazenly conquers stream beds. On the Dana Point headlands, a Canary Islands version of St. John’s wort is squeezing out habitat for rare birds like the gnatcatcher and cactus wren.

Farther inland, Roberts inspects a sage-speckled hillside above a new housing development, pointing out how dozens upon dozens of noxious artichoke thistles are moving over the hill’s crest like a conquering army.

“That’s what most biologists are really scared to see,” he says.

Exotic plants have been arriving in California for centuries, some as early as the 1700s, mixed with cattle feed or in bales of hay. They came from as close as Arizona and as far away as Africa.

More than 1,000 exotic plants have established themselves in the state, most of them in the past 150 years, experts say. The state’s South Coast has the most exotic species, followed by the San Francisco Bay Area and the Central Coast. Nearly one-quarter of San Diego County’s plants are exotic, 27% of those in the Santa Monica Mountains and 41% in the San Francisco area, according to an article in the October issue of the journal Fremontia, published by the California Native Plant Society.

The numbers drop sharply in inland regions. Coastal areas were settled earlier. Seaports drew plants from abroad, and mild coastal temperatures helped them flourish. And California’s many microclimates offered plenty of places where weeds could take root.

“We have as varied a set of habitats as anywhere--topography, climate, soil types. So there’s lots of types of areas for plants to invade,” said John M. Randall, co-author of the Fremontia article and invasive weed specialist for the Nature Conservancy.

Most exotic plants are mild-mannered. But some of the most aggressive weeds are those sprouting free of natural enemies such as insects that curbed their spread in their native lands. That gives them an immediate edge over California’s native plants, which must contend with local pests.

Plants imported for gardening make up fully half of the more than 300 invasive plants in the continental United States and Canada, according to a Brooklyn Botanical Garden handbook that labels as invasive such favorites as foxglove and English ivy. Invasive plants are defined as exotic varieties that run rampant and threaten native wildlife. Some exotic plants can be well-behaved in one region and aggressive in others, an example being baby’s breath, a bouquet staple that is also overrunning Great Lakes dunes.

Some garden favorites are being branded unfairly, said Jack Wick of the California Assn. of Nurserymen. He singled out periwinkle, which has invaded some Bay Area parkland but which he estimates is planted in 100,000 California gardens without ill effects.

Some of the most pernicious weeds were planted for the same qualities that now make them major threats. A prime example is European beachgrass, which the federal government has historically recommended, among other plants, to stabilize West Coast dunes. The grass’ formidable underground stem system has worked too well, holding dunes so firmly that more alien plants could invade, altering natural ecosystems at such landmarks as Point Reyes and Bodega Bay.

“If you want a dunes system instead of, say, a beachgrass garden, you want dunes to move,” said federal ecologist Andrea Pickart, who works at the Lamphere dunes, an area near Arcata where the Nature Conservancy recently spent $350,000 removing beachgrass.

Agricultural Lands Threatened

The federal Bureau of Land Management spent $250,000 controlling weeds in California last year. It asked for an increase to $1.24 million this year--only to get cut back to about $150,000.

“We could easily gobble up $5 million,” said Anne Knox, state weed coordinator for the bureau, which has to pick and choose which weeds to control. “You have to be realistic. If you’re going to control 100 acres of yellow starthistle, and your neighbors don’t control it, is it just going to take over again?”

So how to decide which weeds to tackle? Even California’s two leading weed-fighting groups have differing visions.

The state Department of Food and Agriculture has compiled a Noxious Weed List of 140 plants--exotics making up the vast majority--that threaten agricultural lands.

A second list of 76 invasive plants has been hammered together by the nonprofit California Exotic Pest Plant Council, which focuses on wild lands.

There is little overlap. The state agency is charged with looking at crop lands, not at the wilds. But a similar philosophy pervades policies nationwide, with agricultural weeds dominating the list overseen by the Animal and Plant Inspection Service. The service has been criticized for acting slowly and emphasizing agriculture and insect pests.

The nation’s wild lands are being overlooked in favor of crop lands, say some scientists and land managers who have lobbied hard for a fresh approach.

One major critic of federal policies is Schmitz, who has struggled for decades to remove weeds from the Everglades. Last year, he helped collect petition signatures from more than 500 experts, warning Vice President Al Gore that bio-invasion is destroying natural diversity and costing hundreds of millions of dollars annually.

A special task force was formed, leading to an executive order expected sometime this fall. Early reports suggest that federal agencies will be given basic duties to stop the arrival and spread of exotic species.

“It’s clear we’ve underestimated the effects of invasive species of causing endangered species,” said William Y. Brown, science advisor to Babbitt.

But despite the promise of federal action, many experts are pessimistic about weeds. Even if a Normandy-type assault were to start today, we have already lost part of the war. Some nonnative grasses and other plants appear to be so entrenched that they are now permanent pieces of our landscape.

Some people see a future in which botanists, park rangers and volunteers are forced to hoe nature’s garden year after year to weed out pernicious plants.

“In some places, it’s going to be like the police force,” Randall said. “But it’s worth doing, because if we don’t, we’re going to lose a lot more.”

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The Invaders

California’s wild lands are under attack. Invasive weeds from around the globe grow rampant from Pacific beaches to the Mojave Desert, stifling native vegetation and threatening rare animals. Twelve of the worst invaders, nominated by 18 experts statewide:

1. Edible fig (Ficus carica)

2. Yellow star-thistle (Centaurea solstitialis)

3. Brooms (French, Scotch, Spanish)

4. Giant reed (Arundo donax)

5. Ice plant (carpobrotus edulis)

6. Artichoke thistle (Cynara cardunculus)

7. Cape ivy (Senecio mikanioides)

8. European beachgrass (Ammophila arenaria)

9. Invasive annual grasses (i.e., cheatgrass, or Bromus tectorum; red brome, or Bromus madritensis rubens)

10. Pampas grass, Andean pampas grass (Cortaderia selloana, C. jubata)

11. Perennial pepperweed (Lepidium latifolium)

12. Tamarisk (Tamarix ramosissima, T. gallica, etc.)

The Threatened

Palos Verdes blue butterfly (Glaucopsyche lygdamus palosverdesensis): Found only at a San Pedro military fuel depot, where ice plant encroaches on butterfly host plants.

Western snowy plover (Charadrius alexandrinus nivosus): West Coast shorebird nests in sandy dune areas being overtaken by European beachgrass.

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Web Sites

More information can be found on several Web sites:

* Nature Conservancy (https://tncweeds.ucdavis.edu/tncweeds.html)

* California Exotic Pest Plant Council (https://www.igc.apc.org/ceppc/index.html)

* California Noxious Weed Control Project Inventory (https://endeavor.des.ucdavis.edu/weeds)

* California Native Plant Society (https://www.cnps.org/)

Sources: California Native Plant Society, California Exotic Pest Plant Council, Nature Conservancy, state Department of Fish and Game, state Department of Parks and Recreation, U.S. Bureau of Land Management, U.S. Fish and Wildlife Service, UC Berkeley, UC Davis, UC Santa Cruz, UC Riverside; Researched by DEBORAH SCHOCH/Los Angeles Times

THE DESTRUCTIVE TAMARISK

Introduced in the early 1800s for ornamental use and as a windbreak, salt cedar, or tamarisk (Tamarix ramosissima) is one of the most invasive plants in the Southwest. The plant and its effect on the environment:

HOW THE LAND CHANGES

Areas without tamarisk growth:

* Native plants thrive within 100 yards of a river or flood channel where the water table is higher.

* Diverse plant life (cottonwood, willows, mesquite, grasses and shrubs) provides ideal grounds for birds and insects. Native trees provide good cover and strong branches for nesting.

Areas with heavy tamarisk growth:

* Tamarisk can grow where the water table is deeper because its roots can go deeper than natives.

* Natives choked out by tamarisk. Previously diverse plant life replaced with dense growth of tamarisk.

* Bird population falls. Tamarisk leaves can damage plumage. Birds can’t use the tamarisk’s thin branches for nesting. Displaced birds include least Bell’s vireo, summer tanagers, Southwestern willow flycatchers, yellow-billed cuckoos and the gila woodpecker. Tamarisk can dry up desert springs and watering holes used by animals such as the endangered peninsular bighorn sheep.

WATER USAGE

Tamarisk uses almost twice as much water as natives. Below are average annual figures comparing gallons of water used by natives (cottonwood and willow) and tamarisk on an acre of land:

Cottonwoods and willows: 200,811

Tamarisk: 267,894

*Values calculated by averaging test results throughout the Southwest comparing water use of natives and tamarisk.

SIZE COMPARISON

Cottonwood:

Height: 40’-80’

Trunk diameter: 2’-4’

Branch diameter: 1’ or less

Leaves: 2’-3’ long

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Black Willow:

Height: 20’-30’

Trunk diameter: 8”

Branch diameter: 4-5”

Leaves: 2’-5’ long

Tamarisk:

Height: 60’

Trunk diameter: 2 1/2”

Branch diameter: 2”

Leaves: 1/16” long

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TAMARISK’S ADVANTAGE OVER NATIVES

Seed size: 20 flowers could fit on the head of a penny. Up to 500,000 seeds produced annually per plant. Seeds too small to be eaten by wildlife.

Hardiness: More drought tolerant than natives.

Can regrow from roots even if plant is damaged, submerged or removed.

Salinity: Tamarisk can tolerate high salinity because its leaves secrete salt and deposit it on the soil. Sprouts from native plants can’t tolerate the salinity and are killed off.

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The rooting system

1. Primary root typically reaches 16-20 feet deep. However, phreatophytes such as tamarisk may have roots penetrating as deep as 150 feet.

2. Secondary branching is minimal until primary root has reached the water table.

How deep can the root go?

Average length of root: 20 ft.

Potential length of root: 150 ft.

Matterhorn at Disneyland: 176 ft.

Sources: Erika Zavaleta/Stanford University; U.S. Bureau of Reclamation; Bureau of Land Management; California Exotic Pest Plant Council; Monsanto; Audobon Society Field Guide to North American Trees; Researched by RAOUL RANOA/Los Angeles Times

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