Wind turbine threats to rare bats are debated

Little is known about native Hawaiian hoary bats, or opeapea, including how many of them exist — because the tiny, nocturnal, solitary tree-nesters are difficult to see, much less count.

One thing is clear, however: The rotating blades of wind farm turbines kill the bats, which are listed as endangered by the U.S. Endangered Species Acts and the state of Hawaii.

That’s why the Habitat Conservation Plan put forth by AES, developer of the Na Pua Makani wind project at Kahuku, allows for the take, or killing, of 51 opeapea throughout the project’s 21-year life.

Protesters trying to stop its construction include conservationists who believe far more bats will be killed, as has happened at other Hawaii wind farms.

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At Na Pua Makani, they argue, more deaths will be likely due to the unprecedented size of the turbines — at 568 feet, the tallest in Hawaii.

They’re also concerned about the “cut-in” wind speeds at which the blades will start turning again after being paused during the periods of no or very low wind — when the bats are most likely to be present.

“If the winds are ferocious, the bats can’t hunt, but if the wind is light, there’s more humidity and more bugs and there are more bats flying around,” said state Sen. Gil Riviere (D, Heeia-Laie-Waialua).

Riviere is also a member of the environmental nonprofit group Keep the North Shore Country, which petitioned the Board of Land and Natural Resources to reject AES’ Habitat Conservation Plan during a contested case hearing on May 18, 2018.

The group maintained that the rotors should not be turned back on until wind speeds reached 6.9 meters per second, rather than 5 meters per second, arguing that studies show a 78% decrease in bat mortality at the higher cutoff speed.

Members further complained that Na Pua Makani significantly changed the project, increasing its turbine heights at a late stage, when the plan was already under review by the state Department of Land and Natural Resource’s Endangered Species Recovery Committee, and that turbine heights were not considered in the decision.

“The best available science is, as turbines get taller and rotor sweep area increases, more bats are killed,” said Maxx Phillips, Hawaii director for the Center for Biological Diversity. “Given opeapeas’ low reproductive rate, it’s really worrisome.”

Riviere said AES’ plan based its take estimate solely on data from the smaller Kahuku First Wind, leaving out the Kawailoa Wind Farm above Waimea Valley, which exhausted its 60-bat take in its first seven years and has filed an amended plan seeking permission to kill 220 bats throughout the project’s 20 years.

And, Riviere said, the board didn’t consider that Maui’s Auwahi Wind filed a request to amend its Habitat Conservation Plan to take 140 bats after exhausting the initial approved take of 21 bats. In 2018, Auwahi Wind increased its cut-in speed to 6.9 from 5 meters per second in an effort to reduce bat kills.

Phillips noted that Kawailoa Wind’s amended plan does not increase its cut-in speed. “So if we’re not doing that on the front end of these developments, it’s not going to happen,” she warned with regard to Na Pua Makani.

Riviere’s group filed a lawsuit against DLNR after BLNR approved Na Pua Makani’s plan; state Circuit Judge Jeffrey Crabtree upheld the hearing results Dec. 5 and the case is on appeal.

In an email, Mark Miller, AES chief operating officer for US Generation, said Na Pua Makani’s plan has three protective components: low wind speed curtailment and installation of bat deterrents on each turbine; monitoring harmful impacts to bats and other species below the turbines; and restoration of habitat at the Poamoho Natural Area Reserve.

AES also has pledged $4.2 million to cover monitoring and restoration.

“By preserving habitat outside the wind farm, Na Pua Makani avoids attracting bats near the turbines,” Miller stated.

Riviere countered that “there’s no evidence that repairing habitat will replace even a single bat. The burden is on AES to prove they’re mitigating and minimizing bat kills, and they haven’t done that.”

Recent studies indicate that the bats live in degraded habitats with alien species, as well as in healthy native forests, according Jim Cogs­well, wildlife program manager for DLNR’s Division of Forestry and Wildlife.

At Na Pua Makani, “acoustic deterrents may help” keep bats away from the turbines, said Loyal Mehr­hoff, a former U.S. Fish and Wildlife Service field supervisor and recovery director for the Center for Biological Diversity, who joined DLNR’s Endangered Species Recovery Committee after it approved AES’ habitat plan.

However, he stressed the need to know a population’s size before setting a sustainable take number. “Personally, based on the data I’ve seen, I don’t think we’ve got more than 1,000 bats on Oahu,” Mehrhoff said. “And even if there were 1,500, it wouldn’t be enough to sustain the taking of 200 bats.”

Riviere said his group has applied for a contested case hearing on Kawailoa’s amended plan to take 220 bats, while awaiting the appellate court’s decision regarding Na Pua Makani’s plan to take 51 bats — for starts.