Islands Are Home to Many Unique Plants and Animals : Naturalists Intrigued With Hawaii, an Isolated Laboratory of Evolution

On a hill on the island of Maui overlooking the Pacific, amateur naturalist Michael Severns recently climbed down into a dark lava cave. An owl, spooked by the noise, flew from the shadows, disturbing the silence.

Near the bones of a cow, a dog and other assorted animals, Severns found bones of previously unknown flightless birds that perished more than 1,500 years ago.

For thousands of years an isolated laboratory of evolution, Hawaii is a treasure trove for naturalists who are working to chronicle one of the world’s most unusual ecosystems.

“We’re talking insects, birds, land snails, plants; it’s just a whole new ballgame out there,” said Kenneth Kaneshiro, an entomologist and chairman of the University of Hawaii’s evolutionary biology program. “There’s enough here for dozens of Ph.D. degrees.”

Created by undersea volcanic eruptions, the Hawaiian Islands are separated from continental landmasses by thousands of miles of open ocean. Birds and plants came here by chance, carried upon the winds or washed up by the sea.

120 Bird Species

Provided with a mostly benign climate, new species branched out from a few hardy ancestors. Adapting to habitats ranging from desert lava fields to rain forests to mountains nearly 14,000 feet high, hundreds of plant and animal species flourished.

The U.S. Fish and Wildlife Service estimates that roughly 120 bird species evolved here.

“If Charles Darwin had been able to reach Hawaii, he would have been overwhelmed,” said Alan Marmelstein, area administrator of the U.S. Fish and Wildlife Service here. “What went on in the Galapagos is a fraction of what went on here.”

It was Darwin’s visit to the Galapagos Islands off South America in the mid-1800s that helped him develop his theory of evolution in “The Origin of Species.”

In the book, Darwin argued that animal and plant species constantly evolve through natural selection from earlier species and that surviving species incorporate favorable traits of older species, enabling them to survive.

While in the Galapagos, Darwin found a subfamily of finches with about 12 species or subspecies. By comparison, one family of Hawaiian honey creepers developed more than three times that number of species or subspecies.

For many plants and animals in Hawaii, as in other isolated island settings, species evolution made them vulnerable. For instance, some species of birds gradually lost the ability to fly, finding wings of little use. Plants that once used prickly defenses to ward off foraging animals gradually lost their sharp points.

New Plants, Animals

By the time the early Polynesians arrived here by canoes as early as AD 400, most likely from the south, the Hawaiian Islands had a thriving but delicate ecosystem.

But aboard the sailing canoes of the early Polynesians were seeds of dramatic change in the form of domesticated plants such as taro, yam, banana and breadfruit and animals such as dogs, pigs and rats.

The animals wreaked havoc on the existing animal population. The aggressive four-footed predators found ground-nesting, flightless birds particularly easy prey.

“It would have been like picking grapes,” said Storrs Olson, a Smithsonian Institution paleontologist and ornithologist. “They couldn’t even run fast.”

The early Hawaiians also hunted the birds for food, accelerating their decline. Lowland habitats gave way to farms and villages.

Birds and plant life in higher elevations remained largely undisturbed until the arrival of the English explorer Capt. James Cook in 1778.

Whalers, traders, ranchers and missionaries soon followed, and the upland areas came under assault as settlers built ranches and introduced grazing cattle, goats, sheep and wilder strains of swine.

“So there have been two major waves of extinction: one post-Polynesian and one post-Western contact, and that one still continues,” Marmelstein said. “We’re still seeing species disappearing.”

Many Species Wiped Out

Birds provide the best example.

The Polynesians and the animals they brought with them are believed to have wiped out about 40 species of birds, while another 25 have been made extinct since Cook arrived.

Of the 63 bird species in the United States listed as endangered by the Fish and Wildlife Service, 30 exist only in Hawaii. Hawaii’s two species of native mammals, the monk seal and a species of hoary bat, are both listed as endangered.

Seventeen of the 120 plant species listed as endangered nationwide are unique to Hawaii. Experts say knowledge of Hawaiian invertebrates is still too fragmentary to make any accurate count of how many may be endangered.

Wild goats and pigs continue to threaten fragile plants in several areas.

Aggressive plants introduced from the U.S. mainland and elsewhere can crowd out native plants. New species of birds brought to the islands can threaten vulnerable native species with unfamiliar diseases and can provide competition for food and nesting sites.

Strict agricultural and quarantine inspection regulations are enforced.

On occasion, snakes, which are not native to the islands, have been found and quickly killed. A caiman, a South American relative of the crocodile, was found in an Oahu reservoir in 1984. It was also killed. The animals were believed to have been smuggled into the state and released, apparently by people unaware of the danger they could pose.

While efforts continue to protect what now lives in the islands, new finds are being made.

Flightless Birds

In 1973, biologist Jim Jacobi, participating in a National Science Foundation study of Haleakala Crater on Maui, helped discover a new genus of bird, which was named the Po’o-uli.

After Severns’ find in the Maui cave, Olson from the Smithsonian began digs here that uncovered evidence of 40 to 50 previously unknown species of flightless birds, all wiped out shortly after the arrival of the early Polynesians.

Warren Wagner, a research botanist with the Bishop Museum in Honolulu, has estimated that 960 of the 1,825 plant species that have been chronicled in the islands were either indigenous or endemic to the islands.

“The Hawaiian flora and its animals are so well known all over the world for uniqueness, but people are still just trying to document what is here,” Wagner said.