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Terra-Gen’s Humboldt Wind Energy Project Presents Concerns for Wildlife

Alta Wind Energy Center in Tehachapi, CA, developed by Terra-Gen. Photo: Wikipedia CC.

EPIC and the Northcoast Environmental Center submitted comments in June on the draft environmental impact report (DEIR) for the proposed Terra-Gen Humboldt Wind Energy Project proposed for Monument and Bear River Ridges outside of Scotia. Our detailed comments are available here.

The project as described in the DEIR does not meet the environmental standards nor have the environmental protections we demand. Our organizations urge the project proponents and Humboldt County to undertake additional consultation and outreach efforts to fulfill their obligations to the County’s citizens and our wildlife. While we acknowledge the urgency to develop renewable energy projects to limit the harm of global climate change, the environmental costs must still be fully analyzed and understood before this project can be fully evaluated. As it stands, the DEIR does not account fully for impacts to bird and other species, such as risks to bats and murrelets.

Marbled murrelet at sea. Photo: Craig Strong.

Marbled murrelet at sea. Photo: Craig Strong.

Marbled Murrelets

The marbled murrelet, a small seabird that nests in the mossy branches of coastal old-growth forests, is one of the most iconic species of the environmental movement. This pigeon-sized bird is identified as threatened under both the federal and California Endangered Species Act and is in alarming decline in both Washington and Oregon.

The project is likely to result in the deaths of some murrelets from collisions. There currently are no operational large-scale wind projects within the murrelet’s range, so there is no data concerning murrelets and wind turbines. Absent better data, the project assumes— by looking at other avoidance rates for other species—that murrelets will avoid wind turbines 98 percent of the time they fly through the project area. Based on this projected avoidance rate, the DEIR concludes that the project is likely to kill about 20 murrelets over the 30 years of the project.

The collision risk model, however, is very sensitive to the avoidance rate. A small change in data makes a huge difference. If the avoidance rate dips to 96 percent, the total number of murrelets killed would double.

Given the high uncertainty of impacts, it is critically important that the project avoid impacts first. There are no known measures to avoid harm to murrelets, except avoidance of areas that are likely within the flight paths of murrelets. Harm could also likely be minimized by the curtailment of blade-spinning operations during high-risk periods. The current project, as outlined in the DEIR, fails to do either.

Instead, the project tries to compensate for murrelets deaths by funding projects that seek to increase murrelet nesting success by deterring corvids that prey on murrelet eggs. Such mitigation measures are important, but the purported benefits of this work is largely speculative. Even if the benefits were certain, this appears to be a Faustian bargain—accepting additional and unnecessary murrelet deaths instead of avoiding them where possible.

At a minimum, the project needs to be reformed to avoid murrelet flight paths, as identified through radar surveys, and include operational curtailment during high-risk periods. A curtailment policy should be developed by a panel of species-specific experts based on the best available information.

A hoary bat hangs from a branch. Photo: Tom Benson, Flickr CC.


Acoustical surveys of the project area found that it is used by numerous bats, including those most frequently killed by wind projects: hoary bats, silver-haired bats, and western red bats. All three are migratory bats that exhibit behaviors that put them at high risk for collision and death from wind projects. This project is particularly worrisome because it is so close to an important bat migration hotspot. Every fall, thousands of hoary bats descend upon Humboldt Redwoods State Park, exhibiting a “swarming” behavior that appears to be unique to this region.

The DEIR correctly recognizes that the wind project is capable of producing significant impacts—including the localized extinction of the population or a species-level population impact—but fails to do much of anything to avoid, minimize, or mitigate the harm. Instead the DEIR kicks the can down the road, requiring the establishment of a technical advisory committee to be formed after impacts are measured to examine what can be done. This is not enough.

Thankfully, there is a growing body of science to suggest what can be done. Study after study has found that operational curtailment during high-risk periods is effective, reducing bat deaths anywhere from 44-93 percent with only minimal impacts to power generation. High-risk periods are those when bats are present and active, moving about the air column used by the spinning turbine blades. Determining high-risk can be predicative, using survey information to create models to predict when bats will be present, or informed, using real-time data about site use to inform when to shut off turbines.

The horned lark is one of the most frequently killed species at wind energy projects in the west. Photo: Tracie Hall, CC.

Horned Lark

The coastal prairies of Bear River Ridge are home to a unique population of horned larks. Scientists are puzzled over just what subspecies our local population belong to—either the streaked horned lark (recognized as threatened under the Endangered Species Act) or the California horned lark. Regardless of the taxonomic status, this population is important. It is the only breeding population for a long distance—so long that regardless of the subspecies, this population is likely on a unique evolutionary path. The wind project puts this population at risk.

The horned lark, named for plumage that resembles horns, is one of the most frequently killed species at wind energy projects in the west. The population at Bear River Ridge can’t afford to lose many more. Surveys of the area suggest that there are only seven breeding pairs left. The only way to avoid impacts to horned larks is to not build wind turbines in areas where they might be impacted.


Many species of raptors call the project area home, including bald and golden eagles. This project is likely to kill many of them—although just how many is unclear. Based on fatalities at other wind projects, the DEIR provides a large range of potential takes: a lower estimate at four to 29 raptors per year (based on projects in the northwest), or up to 114 raptors per year, if using data from the “Pacific biofaunal biome.”

Even at the lower estimate, the impacts are significant. Raptors are generally long-lived with a relatively low reproductive rate. They are highly sensitive to impacts, and even small increases in mortality can send populations plummeting. Survey work in the project area has identified a number of species of special concern in addition to bald and golden eagles.

Impacts to raptors have historically been one of the most well documented failings of wind energy projects. Consequently, significant effort has been put forth to find ways to avoid and minimize harm to raptors. The “Top of the World” project in Wyoming, for example, uses camera-aided artificial intelligence to recognize raptors as they approach that wind project, shutting down turbines if the bird is at risk of collision. Similar technology should be implemented for this project.

Necessary Changes to the Project

We are mindful that renewable energy development is not without ecological costs. That said, it can—and should—be done in a manner that avoids, minimizes, and mitigates impacts to the greatest extent feasible. Based on our review of the project, our organizations have determined that the following changes are necessary under state law:

(1) Remove all proposed wind turbines from the coastal prairies of Bear River Ridge. This has been analyzed in the DEIR as the “environmentally superior alternative,” as it presents the least impact while still meeting the project objectives.

(2) Incorporate informed operational curtailment or curtailment during high-risk periods for marbled murrelets, raptors (particularly special-status species and bald and golden eagles), and bats (western red, hoary, and silver-haired bats).

(3) Create a robust adaptive management program throughout the life of the project to monitor operational impacts and to implement, as technology advances, new mitigation measures.

Stayed tuned for updates on this proposed project.

***This article was originally published in the August EcoNews.


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