Draft Guidance Would Further Curb Number of Bats Wind Farms Can Kill

Several million dollars have been spent over the past few years on research, habitat restoration, and land acquisition to mitigate the unexpectedly high number of endangered Hawaiian hoary bats being killed by wind farms across the state.

Last month at the University of Hawai‘i, results from that research were presented in a two-day workshop hosted by the state Endangered Species Recovery Committee (ESRC), which advises the Board of Land and Natural Resources on proposed Habitat Conservation Plans (HCPs) and Incidental Take Licenses required for projects that threaten protected native species.

The results of the various research projects, funded by the wind farms as part of their mitigation efforts, helped fill some of the knowledge gaps surrounding the tiny, solitary creatures, and provided the kind of information that will be helpful in shaping future mitigation and take minimization efforts. Much more is now known about what the bats like to eat, where they like to roost, what island areas see the most activity and when, among other things.

Even so, the studies fell short of providing the data necessary for anyone to definitively say how many bats there are, whether their numbers are declining, and, if so, whether it’s due to a lack of habitat. Perhaps most importantly, it’s still unclear what it will take to offset the losses caused by the wind farms, which is what’s required under the state’s endangered species law.

“Today was supposed to tell me how to grow bats. I haven’t heard anything today,” said ESRC member Melissa Price after the first day of presentations. At the end of the second day, she was still unsatisfied. While she said that huge progress had been made over the past four years of research, “I don’t know how that information plugs into our decisions for habitat conservation plans. How do we get this information to make sure our only terrestrial mammal is still around?” she asked.

Committee members Jim Jacobi and Michelle Bogardus, who helped craft the initial research agenda, admitted that they were perhaps too optimistic that the key questions about the bats would be answered in such a short time.

“The very hard ones were not addressed,” Jacobi said.

Bogardus added that they also underestimated the cost. “We knew a lot less than we do now,” she said. Even so, she added, “Where we had gaps five years ago, we still have gaps.”

To better account for those gaps and help ensure that whatever new or amended HCPs come before it for approval actually comply with state laws that require them to provide a net benefit to native species and the environment, the committee and the state Division of Forestry and Wildlife have drafted a new guidance document.

At the workshop, it was clear that some industry representatives and consultants were concerned about some of the document’s provisions, which departed in significant ways from the current guidance, which was developed in 2015.

When or how the committee decides to revise the document, and what weight it will carry in future decisions, is unclear.

“There is no defined process. We don’t have a timeline. I want to make sure there’s plenty of input. I just want to make sure it’s good,” said David Smith, ESRC chair and administrator for the state Division of Forestry and Wildlife.


The committee has some time to fine tune the guidance document, since it’s already dealt with what were likely some of the hardest decisions it’s had to make. Last year, the committee was asked by multiple wind farms to greatly increase the number of bats they would be allowed to kill over the course of operations. The request by the Kawailoa wind farm on O‘ahu for an additional 160 bats barely won the committee’s approval, largely because of the uncertainty surrounding whether or not the island’s bat population could handle such an increase, especially without any proven mitigation methods.

Committee members were skeptical of Kawailoa’s estimate that there were 2,000 bats on the island. Others complained that, if approved, the facility’s plan would allow mitigation to occur on as little as 20 acres per additional bat to be killed, rather than the minimum 40 acres per bat recommended in the 2015 guidance document.

The new draft document, if closely adhered to by the agencies involved in approving HCPs, might drastically limit the number of bats that can be killed by existing and future wind farms. It would also require facilities to pay more in research funding for additional bat takes, to adopt much stricter minimization measures, and to be able to prove that their mitigation efforts actually work.

“[A]pplicants and agencies should assume, until such time as the best available science informs otherwise, that the Hawaiian hoary bat populations on O‘ahu, Maui, and Hawai‘i are not more than 1,000, 1,500, and 5,000 bats, respectively,” the document states. It also recommends that agencies not approve any cumulative levels of take that exceed the populations’ annual growth rates, unless the expected net benefits to the bats outweigh the potential losses.

While the actual growth rates for these populations is unknown, a 2013 study of bats on Hawai‘i island suggested that in the absence of wind farms, the population there was stable or slightly increasing.

Going on the assumption that the bat populations were stable or slightly increasing, preliminary modeling by the state’s bat task force suggests that wind farms on O‘ahu may be maxed out. With an assumed population of 1,000 bats, the task force’s “best guess” model found that wind facilities on the island could kill no more than 10 bats a year without causing the population to decline. The Kawailoa wind farm alone, before installing acoustic deterrents on all of its turbines last year, had killed an estimated average of 11 a year since 2013. The Kahuku wind farm is estimated to have killed fewer than one bat a year on average since 2010, and the Na Pua Makani wind farm that is not yet operational is expected to kill another 1.7 to 2.5 bats a year.

The guidance document notes that the modeling efforts did not definitively determine how much take should be allowed for wind projects. “They do, however, provide information useful to conservation decisions and assessments on an island-wide basis. … These models indicate that projected levels of take may pose a relatively low risk to large Hawaiian hoary bat populations. For example, if the proposed annual take of bats for the island of Hawai‘i was 10 bats/year and the bat population is expected to be over 5,000, there may be low risk to the population. Conversely, an island with under 1,000 bats may not be able to sustain the loss of 10 bats/ year,” it states.

In many of the facilities’ HCPs, funding bat research was a common initial mitigation measure. Under the 2015 bat guidance document, mitigation expenditures were recommended to equal $50,000 per bat taken. That’s roughly how much it costs to improve 40 acres of forest habitat, the minimum area thought to be required to produce a single bat. This $50,000 per bat formula is what generated the millions of dollars in research funding in 2016.

Studies completed since then on bat core ranges on Maui suggest that they may forage in relatively small areas or exponentially larger areas, depending on the resources available. But until those studies are better understood, the task force chose to rely on a 2015 study that suggested bats spend half of their time in areas that average 48.5 acres. “Doubling the acreage could provide the other half of a bat’s habitat need, if it was of high quality,” the document states. It then suggests that mitigation in the form of restoration or enhancement for a single bat loss should now encompass 97 acres of high quality native habitat.

If facilities want to mitigate their take by funding research instead of habitat restoration, it’s recommended they pay the equivalent of restoration costs: $125,000 per bat. While the document recommends 97 acres/bat for habitat restoration, it concedes that using core use areas to determine the size of habitat mitigation areas has some shortcomings. “The most significant issue is that … it is not known if habitat is a limiting factor. If habitat is not a key limiting factor, then habitat restoration as an offset to take is not only a waste of resources, but it also generates a false assumption, or sense of security, that bat populations are benefitting from the mitigation,” it states.

With regard to efforts to reduce bat kills, the document recommends, among other things, curtailing operations in low wind (at least 5 meters per second and up to or exceeding 6.5 m/s, “when the cumulative take of Hawaiian hoary bats poses a risk to island populations”) and at night.

“Since bats are nearly exclusively nocturnal, HCPs should consider trigger scenarios for which the response [to increased bat take] is to curtail during all night time hours. Adaptive management should include the provision that if authorized take is exceeded, turbines will not operate during times when bat take is possible,” it states.


At the March bat workshop, the ESRC fielded a number of questions from participants about the direction being taken in the new guidance document.

One wind farm consultant asked about where research funding would come from given the stricter mitigation standards being recommended. In addition to the increased costs, the document recommends that for research to be credited as mitigation, projects be designed to “provide information applicable to improving mitigation and planning during the period of the HCP or should provide information on better management actions for Hawaiian hoary bats that will lead to promoting the recovery of the species.”

Bogardus, who represents the U.S. Fish and Wildlife Service on the committee, spoke for her agency, which also approves HCPs and incidental take statements. She said that while there was no question there are extensive research needs for bats and her agency needs that information to make better decisions, for research to now be used as mitigation, it must have on-the-ground benefit for bats.

“It’s a hard bar to reach. … We barely made it happen [last time]. I don’t think we could make it work for those same research projects today. In order to make it happen, it has to be very tailored,” she said, adding that facilities should work closely with the service to ensure the research informs actual bat management efforts.

“We obviously need other funding streams for bat research [but] research is unlikely to be used for mitigation credit,” she said. She added that even if it’s not given any mitigation credit for research, the industry would benefit from funding research on its own, particularly on deterrents.

Committee member Price reminded everyone that Hawai‘i’s endangered species law requires that mitigation efforts provide a net benefit to the species being harmed. “If you can’t show that, we can’t vote yes. That’s our job on this committee. The problem is we don’t know those answers … so you’re stuck stabbing in the dark if you don’t have answers. You gotta prove you can grow bats,” she said.

“It’s net environmental benefits. The law says net environmental benefits,” committee chair Smith countered, suggesting that those benefits need not apply strictly to the bats.

“So can we cause a species extinction?” Price then asked.

“It’s not that clear,” Smith replied, adding that he has been talking with state deputy attorney general Linda Chow, “trying to figure it out.”

Committee member Loyal Mehrhoff pointed out that the draft guidance document includes a checklist for HCPs that is supposed to help applicants ensure that they meet legal requirements.

Marie VanZandt, who works for the company that runs Maui’s Auwahi wind farm, expressed concern about some of the proposed minimization recommendations. She noted that Auwahi has already adopted a high minimum wind speed for operations, 6.9 meters per second, and was willing to try bat deterrent technologies, despite questions about whether or not they would work for the site. “We want to do the right thing. We want to reduce bat mortality,” she said. But when it came to the recommendation to curtail operations at night to avoid excessive bat take, she balked.

“We can’t shut off the wind turbines at night; otherwise, we’re a solar farm,” she said.

She said she submitted a comment letter to the ESRC advocating for more industry involvement in the development of the guidance document. “It’s going to be important to understand the practicability of the recommendations,” she said.

Another meeting participant asked how the guidance document, if adopted, would be used.

“If this is rule-making, we should be explicit. I would like to see something in the document saying it’s not a rule. … It looks like a regulatory document, not a guidance document,’ he said.

Bogardus said that the original 2015 version was never intended to be part of rule-making, but was to serve as a guide to help avoid delays in decision-making. “It was always open if people wanted to pose other things. … The committee would have to discuss that. We saw that happen. At the end of the day, it’s guidance. It was never intended to be, ‘thou shalt do it this way,’” she said.

“This has been one of the hardest issues the Fish and Wildlife Service and DOFAW and ESRC faced,” she said, and praised the industry for its role in supporting all of the new research on bats. “Is it everything we need? No. Is it everything we want it to be? No, but it’s a hell of a lot more than they knew a few years ago,” she said.

Smith said he wanted to continue discussions among all the parties, both inside and outside ESRC meetings. “We’ve got the regulatory stuff dealt with for the time being. Hopefully, we can be more proactive,” he said.

— Teresa Dawson

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