FIGHTING BACK:
Keeping Paradise Safe for the Natives
Richard Stone
KULANI, HAWAII--When the Kulani Correctional
Facility took in 400 fresh inmates in May, the hope was that the new
prisoners, and their descendants, would be locked away for the rest of
their lives. Not that these wards of the state were guilty of any crime:
They were sent to Kulani because the 3000-hectare prison grounds and
adjacent state and private reserves are part of an innovative program to
protect native species from the ravages of invaders. The young
inmates--seedlings marked by pink flags amid the surrounding grass--are
endangered Mauna Loa silversword, a majestic plant with silvery, sharp
leaves and a massive flowering stalk that blooms once and then dies.
Sheltered inside a pig-proof fence, other native species are mounting
comebacks too: Tree ferns, their starchy cores now off limits to pigs, are
thriving. Native songbirds, driven from the lowlands by a triple
whammy--habitat loss and avian malaria, plus invasive species that prey on
their eggs--flit from branch to branch in the gnarled ohia forest.
The silverswords and songbirds are refugees from a war that has taken a
heavy toll on Hawaii's native life-forms. Islands are particularly
vulnerable to biological invaders, and Hawaii has suffered wave upon wave
since the arrival of the first Polynesian settlers some 2000 years ago.
Although it's hard to assign full blame to an invader for any particular
extinction, statistics tell a sad tale: Of 140 known native bird species,
70 have gone extinct since human arrival, and 30 are on the endangered
list. "Alien species are the biggest problem we're dealing with
now," says Jim Jacobi, a botanist with the U.S. Geological Survey's
Pacific Island Ecosystems Research Center in Hawaii. And as one of the
hardest hit places on Earth, Hawaii has come up with an innovative way of protecting
natives from invaders. Instead of trying to eliminate established exotic
species--a nearly impossible task--Hawaii is creating well-defended
reserves where native species can find refuge.
Hawaii's menagerie of imports includes plenty of unpleasant customers.
Take the rosy wolf snail, Euglandina rosea. It was imported in
1958 to knock off another alien predator, the giant African snail, and is
an ideal killing machine, tracking its victims by their slime trails.
However, Euglandina swiftly developed a taste for the native
snails too and went on a binge. "It's very difficult to prove that Euglandina
is responsible for the extinction of native snails, but the weight of the
evidence virtually forces this conclusion," says Robert Cowie, a
biologist at the Bishop Museum in Honolulu.
Wiping out Euglandina is almost impossible--"everything
you think of that can kill Euglandina would kill the native snails
as well," says Stephen Miller, a population ecologist with the U.S.
Fish and Wildlife Service in Honolulu. So scientists have for now forsaken
the sword for the shield: snail "exclosures" designed to protect
the natives from the exotic predators. A team led by zoologist Michael
Hadfield of the University of Hawaii, Manoa, has built the largest of them,
a 430-square-meter corrugated aluminum fortress, in the northern Waianae
mountains on Oahu. Erected around a population of endangered Achatinella
mustelina snails, the barrier is ringed by a salt trough, a substance
as painful to snails as battery acid to people. "The minute Euglandina
touch the salt, they just drop back," says Hadfield. The fence also
has two electrified wires to deter rats, another snail predator, and rat
motels inside the exclosure.
Across the state, land managers are protecting other natives by throwing
up fences and hunting down the exotics that remain inside. "Fencing of
native preserves is considered state of the art," says Dave Bender, a
restoration ecologist with the National Tropical Botanical Garden on Kauai.
At Volcanoes National Park and on adjacent public and private lands on the
northern slope of Hawaii's Mauna Loa volcano, managers have fenced off
thousands of hectares of forest. Staff hunters have killed nearly all the feral
pigs in the protected area. And from a population of 20,000 feral goats
several years ago, the park is down to about a dozen "Judas"
goats, allowed to stick around to attract any goats that sneak through the
fence. Scientists keep tabs on the Judas goats, fitted with radio collars,
and shoot any new faces. Next on the hit list, says Jacobi, are bird-eating
feral cats--a controversial move among cat lovers--and nasty invasive
plants like the yellow Himalayan raspberry, whose heart-shaped leaves belie
its aggressive advance across the islands.
Of course, biologists would rather not have to build such reserves, so
they are trying to prevent new threats from spinning out of control. After
seeing the devastation that a Central American tree called Miconia calvescens
has visited on Tahiti--where it covers 75% of the island and has earned the
nickname "the green cancer"--Hawaiian biologists Betsy Gagne and
Steve Montgomery mounted a 15-year-long campaign to get the tree on
Hawaii's Noxious Weed list, which would prohibit its import. They finally
succeeded in 1992. Since then, Maui and Hawaii have launched 10-year
programs to eradicate Miconia, a laborious job that involves
applying a thin line of herbicide at the base of each tree. It's working:
So far, mature Miconia plants have been eliminated from 70% of
Hawaii island, although all these areas must be treated again as the seed
bank sends up shoots.
Hawaiian scientists have also lobbied to close the border to potential
invasive species, but they have been opposed by horticultural interests.
"I know the nursery industry would kill me if they heard me say this,
but we need a broader list of plants that are prohibited," says
Charles Lamoureux, director of the Lyon Arboretum in Honolulu. Others
suggest a "white list" of permitted plants, such as exists in
Hawaii for animals. "If we don't act now," says Jacobi,
"we're going to have a much harder time dealing with the problem as
time goes on."
