Project would kill off rats to create refuge for seabirds

The state wants to eradicate rats on a small island off Niihau to create a refuge for threatened and endangered seabirds as rising sea levels threaten low-lying atolls.

A public informational meeting by the state Division of Forestry and Wildlife is scheduled for 5 to 7 p.m. Tuesday at the Waimea Neighborhood Community Center on Kauai. Officials plan to discuss the proposed eradication project in an effort to restore the ecosystem on Lehua Island.

The project is the state’s second attempt to eradicate the rats; its last attempt in 2009 was unsuccessful.

The state described Lehua Island as “one of the largest and most diverse seabird colonies in the main Hawaiian Islands.”

With the threat of sea level rise to atolls within the Papahanau- mokuakea marine sanctuary, the island could serve as a refuge for seabirds displaced by the effects of climate change, said Patrick Chee, small mammal control planner with the division, part of the Department of Land and Natural Resources.

Rats pose a particular threat to ground-nesting birds like Newell’s shearwaters as they consume eggs, hatchlings and, at times, adult seabirds, Chee said. A draft environmental assessment on the Lehua Island Ecosystem Restoration Project said eradication efforts may improve the island’s habitat and aid in the recovery of species such as the shearwaters, band-rumped storm petrels, Hawaiian petrels, and native plants and insects.

Lehua Island is a 284-acre island located nearly a mile off Niihau and is managed by DLNR as a seabird sanctuary. Chee said the island is ideal as a refuge for seabirds because it’s 700 feet above sea level.

Like atolls in the Northwestern Hawaiian Islands, islets in the main Hawaiian Islands are threatened by rising sea levels.

“More the reason for us to pay attention to higher islands like Lehua,” Chee said.

The cost to eradicate rats is estimated at a little more than $1 million. The state plans to start monthlong eradication efforts in August.

Chee said the estimated number of rats on Lehua Island is unknown, but they’re believed to be in low densities.

The rats will be poisoned with a compound known as diphacinone distributed as cylinder-shaped pellets, the draft assessment said. This is the same rodenticide used to eradicate rats at Mokapu Island off Molokai.

Polynesian or Pacific rats were introduced to Hawaii in the 18th or 19th centuries by Polynesian settlers, according to the draft assessment.

Rats and rabbits — the latter first spotted on the island in 1936 — devastated the ecosystem on Lehua Island.

In 2006, the state eradicated the rabbits through hunting. Vegetation began to flourish following the rabbit eradication and led to less soil erosion, stabilizing the grounds for nesting birds.

Three years later, the state tried but failed to rid Lehua Island of rats. The problem, Chee said, could have been that they set out the pellets during the winter season, when there was more vegetation for the rats to eat and more rain that likely washed away some of the poison.

In this year’s proposed project, the rodenticide will be applied in the fall when the weather is dry and there is less likelihood of the poison reaching the ocean.

Because of the island’s steep terrain, a helicopter will fly over Lehua Island to evenly spread the rodenticide on the ground from a hanging bucket.

“The eradication is completely dependant on the rodenticide,” Chee said.

The state also has worked with Island Conservation, a group that has a good track record of rat eradication, to restore ecosystems.

The deadline to submit public comments on the draft environmental assessment is April 7. Comments may be emailed to LehuaRestoration@hawaii.gov.

To review the draft, visit 808ne.ws/lehuaisland.