Alien Invasion, Part 1:

The Big Picture

When Europeans set foot in America, an alien invasion began. This invasion was comprised of people, plants, animals or any organism from another country that was introduced and thrived under local North American conditions. Some of the most notable examples include Asian flu virus and zebra mussels; European diseases, starlings, sparrows and grasses; African aids virus and Africanized honey bees; Australian eucalyptus trees; and weeds from all over the world. The California Exotic Pest Plant Council (Cal-EPPC) lists the most invasive wildland pest plants in publications and on its web site. The California Department of Food and Agriculture (CDFA) and the United States Department of Agriculture (USDA) have data on the most troublesome agricultural pests. Unfortunately, the introduction of alien organisms increases each year with the increases in the speed and number of transoceanic shipments and travels by tourists and business people. This trend may be expected to continue.

In California, the rise in alien species took a large jump in the 1850’s with the flood of human immigrants during the gold rush. The population of outsiders exploded, and so did the carrying-in of alien organisms. Large quantities of foreign species came into California as deliberate or accidental agricultural imports. Smaller but significant numbers of aliens came in as ornamental horticulture imports. Some aquatic aliens attached themselves to ships and infested our harbors. Additionally, tourists and businesses accidentally or deliberately brought in other pests.

While the alien invasion has been proceeding on a statewide, national and global scale, most efforts at eradication have been proceeding on a local or county scale. Few efforts other than disease and some agricultural pest eradication have been on a state or national scale. Thus, many of the aliens have been gaining the upper hand in California and other regions for over a century.

At least a dozen invasive species are scattered through the Elfin Forest Natural Area. These species make a home here, especially in areas where these sand dunes have been disturbed, and seeds can take root. Human activities have badly eroded and denuded some areas of the sparse dune ground cover. This abuse continues to this day with human and pet traffic on the dunes and fragile native vegetation. Wild game used to create narrow avenues with minor plant damage. Now, humans and pets have greatly increased the amount of damage, leaving wide avenues of open sand and broken vegetation. This invites increased erosion and sedimentation of Morro Bay, or invasion by the aggressive aliens.

The alien invaders come to America’s landscape with no natural predators to hold them in balance. Often they are prodigious multipliers. Some individual plants can produce thousands of seeds in a given year. The average invasive plant spreads 15% per year where there is ample water, such as in riparian areas like creek beds. That translates to a doubling in the number plants or infested acreage about every five years. Given the current degree of infestation in the Elfin Forest, the entire park could become infested with one or more invasive alien species within our lifetimes.

The dune scrub and chaparral in the park are being invaded currently by veldt grass and narrow-leaved iceplant. The infestation is quite bad in the southern two-thirds of the park. In places veldt grass has nearly obliterated the other species. Both invasive species are encroaching on the oak and Morro manzanita groves. The iceplant flourishes in the open spaces along trails in the sand and where a large manzanita plant has died. The veldt grass is more indiscriminate and encroaches everywhere. Efforts to spray veldt grass in the mid-1990’s had the infestation nearly controlled. Today, delays in following up with a multi-year treatment (due to endangered species legal issues) has allowed the infestation to expand to nearly all corners of the park. Even without the potentially harmful effects of herbicide, the endangered El Moro Shoulderband dune snail is sure to suffer from this loss of habitat. When the grass moves in, the native plants favored by the snail are eradicated. The threatened Morro manzanita also is in danger from the weed infestation. As the pest plants encroach on the manzanita stands, fewer can reproduce and continue the species.

Some of the other invasives are attacking the pygmy oak trees. So-called smilax, cape ivy, and English ivy are smothering the trees, blocking their sources of sunlight and nutrients. The upper six inches of the soil under smilax-infested oaks is a mass of interlocking tuberous roots. Whole forests in New Zealand have been smothered by “smilax” and cape ivy.

Italian thistle is pushing out the native vegetation from the understory of the oak groves. This also is changing the habitat needed for survival by the endangered dune snail.

Two open meadow areas in the Elfin Forest are infested with Malta starthistle. This scourge is found as far away as Washington State and the eastern U.S. More locally, it is also in nearby land east of South Bay Boulevard.

Not only are the present aliens in the Elfin Forest a concern, but there are also nearby species that could strike at any time. Birds, land animals, water, wind, and careless hikers could spread invasives such as giant reed (Arundo donax) from nearby creeks or could spread pampas and jubata grass (Cortaderia selloana and Cortaderia jubata) from nearby landscapes.

Given the state of the invasion and the potential for ecological disaster, only continual vigilance will allow the Elfin Forest to survive in a native state. Weed surveys need to be done each year, and yearly weed abatement and replanting with native species have to be done. Given limitations in funding and manpower, priorities will have to be established and reviewed each time a change is noted. Preservation and conservation of the park and all of coastal California will be never-ending tasks. The nature preserve needs committed volunteers like SWAP to ensure its healthy survival.

First Weed