Rats and other
nonnative creatures imperil the existence of the Hibiscadelphus
giffardianus in the state most plagued by endangered species.
By JENELL TALLEY
Hawaii and one conjures up images of luaus, flat-tummied hula dancers in
grass skirts, beautiful beaches, clear blue water, and palm trees swaying
in the wind. But there's another image not so striking: Hibiscadelphus
giffardianus, a tree species not nearly as plentiful as the palm,
facing the threat of extinction.
giffardianus, also called hau kuahiwi, is endemic to Hawaii Volcanoes
National Park. The species was first described in 1911 by Austrian
botanist Joseph Rock. Before the original tree died in 1930, cuttings were
collected and at least one tree was propagated on land adjacent to what is
now Hawaii Volcanoes. This tree died in 1940, but one cutting remained,
keeping the species alive. The plant survived in cultivation and was
replanted in the park in the 1950s. The species has been reduced to a
single tree at least three times. Each tree is derived from the 1911
H. giffardianus is
one of seven Hibiscadelphus species, each endangered or extinct.
Only ten adult trees remain in Hawaii Volcanoes, each at least 40 years
old, and only 11 young plants survived plantings that occurred in 1995 and
1997. The trees look much like a large hibiscus, not surprising since Hibiscadelphus
means "brother of hibiscus." They typically grow 30 to 50
feet tall and have multiple trunks. The tree has rounded leaves that are
large and rough. During the spring and summer, dull maroon flowers cover
the tree. The curving flowers are narrow, reaching two to three inches in
length. The tree produces yellowish-green seedpods, or dry fruit, about an
inch long, most commonly during the summer and fall.
The Kamehameha butterfly has
been observed feeding on the trees' flowers, and native birds were once
known to feast on the nectar, though this is seldom seen today. Alien
insects, such as the two-spotted leafhopper and the Japanese rose beetle,
feed on the leaves. The insects may be contributing to the trees' demise,
but rats are a bigger culprit, says Thomas Belfield, a rare and endangered
species propagation specialist at Hawaii Volcanoes. "Rats are the
biggest threat facing the trees," Belfield says. "Rats eat seeds
and girdle branches." For H. giffardianus, which propagates
from its seeds, this causes a serious problem. In addition to the threat
posed by alien species, the trees suffer from the loss of a native bird
species. The long-billed honeycreeper, likely the flowers' original
pollinator, is rareif present at allin the park.
Steps are being taken to
increase the tree population, although currently Belfield, Linda Pratt, a
botanist working for the U.S. Geological Survey Pacific Islands Ecosystems
Research Center, and Tim Tunison, chief of resources management at Hawaii
Volcanoes, are the only scientists dedicated to the recovery effort. The
tree has no specific recovery program, but Belfield is working on the
park's Rare Plants Stabilization Project, which began last year. The
project focuses on examining the status of rare and endangered plant
species, including the H. giffardianus, in four ecological zones in the
park. Seeds, fruit, and cuttings are collected and raised in the park's
greenhouse, then planted in the park.
More than 200 trees have been planted in the last few years as part of an
experiment conducted by U.S. Geological Survey researchers to study damage
caused by rats. Despite these efforts, more work remains before the trees
can make it off the endangered list. "It is unrealistic to imagine
that this species will ever be delisted unless it goes extinct,"
Pratt says, adding, that reintroducing the species to its natural habitat
and having it be self-sustaining is the park's goal.
JENELL TALLEY is