The Hawaii Supreme Court heard oral arguments Thursday in a dispute that ultimately comes down to how many endangered Hawaiian hoary bats a Kahuku wind farm is allowed to kill.

The controversial Na Pua Makani wind farm made headlines a couple of years ago when about 200 people were arrested trying to stop its massive turbine parts from being hauled from the port at Kalaeloa to Kahuku.

Now the 24-megawatt project by Na Pua Makani Power Partners LLC is at the center of a legal dispute with the nonprofit Keep the North Shore Country over the developer’s habitat conservation plan and incidental take license, which allows the spinning turbines to kill 51 bats, or opeapea, over 21 years.

The state Board of Land and Natural Resources voted 5-1 in 2018 to approve the habitat conservation plan following a contested case in which the hearing officer concluded that the plan did not comply with environmental laws.

Keep the North Shore Country appealed the ruling, but in 2019 a Circuit Court judge found no error in the board’s decision- making process.

Judge Jeffrey Crabtree noted that BLNR had appropriately relied on the expertise of its Endangered Species Recovery Committee, a panel he said undertook a serious effort to collect information that informed and guided decision- making to preserve and protect the opeapea.

Crabtree said the court was satisfied that the board’s decisions were made on the best available data and that the estimate of bat deaths in the incidental take license was reasonably adjusted to account for several uncertain factors.

Keep the North Shore Country appealed again, and it landed at the state Supreme Court earlier in the year.

On Thursday the dispute was heard by the high court during a virtual online court hearing.

“This case is about an administrative agency failing to follow the standard set by the Legislature regarding the protection of endangered species,” the nonprofit’s attorney, Lance Collins, told the justices.

“The BLNR failed to do this when, in overruling the hearing’s officer, it applied the wrong standard in evaluating the evidence and glossed over the failure of the applicant to meet its burden,” he said.

Collins said the board didn’t get the full picture about how vulnerable the bats are on the North Shore because it relied only on bat-kill data from the neighboring wind farm. He said it was tantamount to a climate denier cherry-picking the evidence to support his case.

“Every wind-power project in Hawaii has killed opeapea,” he said. “Every habitat conservation plan approved in Hawaii has underestimated how many opeapea would be killed.”

But John Manaut, attorney for Na Pua Makani, told the justices that the conservation plan is based on the best available science, compiled by the members of the Endangered Species Recovery Committee and two experts who testified at the contested case hearing.

“They all concluded the plan was designed to enhance the likelihood of the bat’s survival and recovery as a species,” he said.

Manaut added that even if estimates are proved wrong, the wind farm’s operations can be modified to lessen the impact on the species.

Collins also argued that BLNR failed to afford his clients due process when it allowed Samuel Gon III, a biologist, to sit on the Endangered Species Recovery Committee and then vote for the project as a member of the Land Board.

State Deputy Solicitor General Ewan Rayner countered that the Legislature, by statute, allows the BLNR chairman, or designee, to sit on both panels, so there’s no reason another member wouldn’t be allowed to do the same.

Gon is a senior scientist at the Nature Conservancy of Hawaii and an expert on Native Hawaiian biology and culture.

Scientists estimate there are between a few hundred and a few thousand Hawaiian hoary bats in the main Hawaiian Islands. The state’s only land mammal, the opeapea is a long-lived species with low reproductive rates, making populations susceptible to localized extinction.

Na Pua Makani is an eight-turbine project that will not only help Oahu reduce its dependence on fossil fuels, but avoid almost 1 million tons of carbon dioxide over 20 years, Manaut said.