Fighting the Island Invaders

Almost since an age more than 6 million years ago, when the Earth’s crust first hoisted Santa Catalina Island above sea level, plant and animal life on this craggy island has flourished in splendid isolation.

Protected from the mainland by about 20 miles of ocean, the island’s patchwork terrain of arid mountain slopes, fog-dampened valleys and rocky coves has fostered more than a dozen unique plant and animal species. A natural lack of predators and grazing animals on the 76-square-mile island seemed to promise endless prosperity for all of Catalina’s flora and fauna.

Or at least that’s how it appeared before the 18th century--before the enterprising hands of European explorers, smugglers and settlers first began tinkering with the island’s natural development. In just a few centuries, these visitors brought with them an invading force of Old World plants and animals that turned the island’s evolution on its head. (Although Native Americans settled on the island more than 7,000 years ago, long before Europeans ever arrived, their impact on fauna and flora was minimal in comparison.)

The invaders have included thousands of goats, left by sailors as a source of food on return visits; antelope and deer, imported for game hunting; bison; pigs; and scores of prickly and bitter weeds. In most instances, the newcomers brought havoc for the native flora and fauna, which had few natural defenses. Goats and pigs in particular have gobbled, trampled and otherwise eliminated 48 species of native plants, including Trask’s monkey flower, which was found only on Catalina and is extinct.

Bullets, Traps, Herbicides and Shovels

Today, humans are trying to set the environmental record straight. The Catalina Island Conservancy, a nonprofit organization whose mandate is to return the island to its natural state, has variously employed bullets, traps, herbicides, saws and shovels in this ecological feud.

The conservancy, which owns 86% of the island, was formed by the Wrigley family of Chicago. The Wrigleys, of chewing gum fame, began purchasing portions of the island in 1919, with an eye toward resort tourism. Gradually however, the family took up the cause of environmental preservation.

Their efforts have included the use of helicopters and volunteers who hike into steep, remote valleys to spray, uproot or cut down invading weeds and trees. At times, the organization has been criticized for these tactics. Recently, animal rights activists accused the conservancy of cruelty in its goat hunts--a charge that ultimately forced the organization to capture the goats alive instead of killing them. Still other critics accuse the conservancy of being too passive.

The conservancy says it has made great strides with its restoration efforts in the island’s rugged interior, of which most visitors to Santa Catalina see little because they spend much of their time in the densely populated city of Avalon. But there have also been setbacks. Recently, a plague of canine distemper, brought to the island by a nonnative dog, has wiped out most of the native Catalina Island fox population. The fox, a species unique to Catalina, numbered in the thousands only two years ago. Today, fewer than 70 remain, and officials are working feverishly to develop a vaccine for the virus.

The conservancy has all but conceded defeat in some battles, especially those involving invading shrubs and grasses. “They’re our biggest problem, but one we’ll never control,” said William Bushing, the conservancy’s director of ecological restoration programs.

The reason for such pessimism has much to do with the ways nonnative plants and animals support each other. One such tag-team relationship involves the island’s feral pig population and a prolific shrub called Mediterranean broom.

Feral pigs became a problem after the 1920s, when domestic pigs were brought to Catalina in hopes that they would eat native rattlesnakes. They never made a dent in the snake population, but some escaped from captivity and gave rise to a teeming population of about 1,000 tusked and shaggy feral pigs. The pigs have destroyed hillsides of native plants by rooting for bulbs, churning the soil like rototillers.

After the pigs pass through, conservancy officials say, the Mediterranean broom very quickly takes root in the tilled soil, denying the native grasses and bushes an opportunity to grow back. A prolific yellow-flowered shrub, the Mediterranean broom was introduced to the island in the 1920s for landscaping. Like many others among Catalina’s 250 species of nonnative plants, its seeds are often spread in mud and dirt in automobile tires and underbodies. The broom plant has choked out many native species and offers no sustenance to native animals like the Catalina fox.

The conservancy said it has slowed the spread of feral pigs in the last year with the construction of more than 60 miles of so-called “anti-pig fencing.” The fences rise roughly four feet off the ground and each is topped with a strand of barbed wire. They divide the island into four management zones in which the pigs are hunted and trapped. The conservancy hopes to remove all pigs within the next two or three years.

Controversial Decision on Bison

Unlike its management of goats and pigs, the conservancy has not targeted bison for removal from the island.

The bison were brought to the island in 1924, when 14 of them were used in the silent film “The Vanishing American.” Then they were left behind. Today more than 200 of the beasts can be found on the island. Recognizing the value of the animals as a tourist draw, the conservancy has decided to maintain their numbers at 225. Bison above that number are corralled, removed and sold.

Some ecologists oppose this approach and insist that bison be eliminated from the island. They say bison’s grazing will continue to damage native plants. They say that bison’s droppings are spreading the seeds of nonnative plants and greatly increasing the native fly population.

“The bison really need to go,” said Robert van de Hoek, a biologist and former supervisor of Los Angeles County’s Catalina Interpretive Center. “The conservancy has taken a real scattershot approach to some of their problems. I think they can still win this one, but not like this.”

Although the conservancy’s efforts to control nonnative animals have won it the most attention, directors say the issue of plants is of equal or greater importance.

In addition to spraying nonnative plants with herbicides, or uprooting them, the conservancy has begun an ambitious program for replanting native species. This program involves the collecting and storage of seeds at a special native plant nursery and the sowing of 1 million plants. Because the conservancy estimates that it will take 30 years to complete the project, Bushing said the restoration efforts probably would continue for some time.

“I think we’ve got job security for our lifetimes and probably beyond,” Bushing said.

(BEGIN TEXT OF INFOBOX / INFOGRAPHIC)

CATALINA: The Evolution Next Door

Dozens of nonnative plant and animal species inhabit Santa Catalina Island. Although the Catalina Island Conservancy has been charged with returning the island to its natural state, officials concede that it is impossible to reach that goal. Instead, the conservancy has targeted specific plants and animals that they view as being the most potentially damaging to the island’s native inhabitants. Goats and feral pigs in particular are accused of gobbling, trampling and otherwise eliminating 48 species of native plants, including Trask’s monkey flower, which was found only on Catalina and is extinct, according to the conservancy.

The following are among the native and nonnative plants and animals currently found on the island:

*

Source: Catalina Island Conservancy, U.S.G.S.; Researched by MONTE MORIN /Los Angeles