Bighorn sheep, © Gary Stolz/USFWS

Long Lines, Smart Lines: Planning Wildlife-Friendly Corridors for Renewable Energy Transmission

Quick, how does electricity get from an Arizona solar plant to a Phoenix office park? If you answered “power lines,” you’re right! As we build more wind and solar power throughout the West, we will need to think carefully about how to get that renewable electricity to the towns and cities where it’s needed. In the video below, I take a tour of Maricopa County, west of Phoenix, where a lot of solar energy development is happening or being proposed. On the tour, we looked at alternatives for planning new or expanded power line, or transmission, corridors to move energy from the solar plants being constructed throughout the area. In the rest of this post, I’ll describe what Defenders is doing in Arizona to help ensure that, these transmission corridors get planned in a way that is “smart from the start,” just as we do with the renewable energy projects that they are meant to connect with.

Potential transmission line paths, © Center for American Progress

Theoretical paths for new transmission lines to link renewable energy generation to markets.

Wildlife-friendly Renewable Energy needs Wildlife-friendly Transmission Lines

Often called “the largest and most complex machine ever built,” the American electrical grid is called upon to meet many needs. Despite some of its parts being as many as 130 years old, it must deliver its electricity reliably 100% of the time to customers who expect that flipping a switch will always turn the lights on. It must march long distances carrying high-voltage loads in thick cables, and then step down into the fractal network of distribution lines that bring power to houses and businesses. It must be repaired quickly after storms. And it must do all of this while operating under a patchwork of ownership and regulatory structures, without any centralized planning authority.

As our population grows and our energy production shifts from fossil fuels (particularly coal) to renewable energy, our demands upon the grid will grow and change as well. Now, in addition to many other needs, we need new connections to bring solar energy from the deserts and wind from the Midwestern plains to the cities of the coasts. Just as we work hard to ensure that renewable energy generation plants are built “Smart from the Start,” Defenders is working to ensure that these new transmission corridors are also designed right and traverse our treasured landscapes with as little impact as possible on those lands, the habitats they encompass, and the wildlife that rely on them.

Javelina, © NPS

Javelina (a species of peccary) are an important prey species for mountain lions that use desert washes and thick vegetation as travel corridors.

How Transmission Corridors Impact Wildlife

Transmission corridors can affect animals in a number of ways. Some species, like desert bighorn sheep and javelina, are impacted by roads and increased human development that create barriers in their migratory and travel routes. Part of the careful planning of energy corridors for these kinds of wide-roaming species involves incorporating protected crossing structures that provide safe places to get over, under, or around roads, pylons, and other obstacles. Other animals, like young Sonoran desert tortoise, are vulnerable to increased predation by birds like ravens that use new transmission lines as perches to extend their hunting ranges and feed on tortoise eggs and young. To minimize this threat to the tortoise, it’s important to place new power lines along already-existing corridors so that ravens aren’t introduced to new areas. Some rare animals, like Mojave fringe-toed lizard, are vulnerable in their small patches of unique habitat. Corridor planning must take care to avoid these habitats. Finally, some critters with very specialized habitat needs, like Arizona’s great diversity of amphibians, may be impacted by construction or operations. Corridor planning must specify that operators use good design and management practices – such as setting poles on either side of a dry desert riverbed to hang the power line over it rather than building in it, or providing ample culvert crossings under roads in sensitive areas – that will help avoid impacts to these species.

Desert bighorn sheep, © Steve Young, NPS

Desert Bighorn Sheep migrate long distances and are sensitive to linear disturbances that disrupt their migration routes if not properly mitigated.

Smart Siting in Arizona and Across the West

Defenders is vigilant about working to minimize impacts to wildlife. In Arizona, Defenders is an active participant in the Arizona Solar Working Group, a collaboration between conservation and wildlife organizations, renewable energy advocates, utilities, and solar developers working toward a sustainable energy future. The group was formed to provide input and to make recommendations to the Arizona Bureau of Land Management as it developed its innovative Restoration Design Energy Project (RDEP), and has since turned its attention to helping solve transmission siting challenges in the state.

Now, we are working together to provide recommendations to the BLM and the U.S. Forest Service as they review corridors designated for future energy transmission across public lands in 11 Western states. Originally proposed in 2009, these corridors did not do enough to connect renewable (rather than fossil fuel-generated) energy to towns and cities, did not provide enough opportunity for public input on their construction, and did not adequately analyze potential impacts on wildlife and the environment. In response, Defenders joined fellow conservation organizations and one county in challenging the designation of the originally proposed corridors. The litigation resulted in a settlement agreement, in which the agencies will review the corridors to address these issues.

Right now in Arizona, the working group is focusing on making recommendations for three corridors that are likely to connect with the strong solar resource in the southwestern part of the state. These include identifying a new route to replace the corridor roughly connecting Phoenix and Las Vegas that was deemed “of concern” in the 2012 settlement agreement, and analyzing options to improve corridors along I-10 and I-8 heading west from Phoenix to southern California. Defenders is using GIS expertise to provide the group with mapping of wildlife movements and habitats to ensure that our recommendations conserve Arizona’s unique desert wildlife across the landscape.

West-Wide Energy Corridors in AZ, © BLM & Defenders of Wildlife

West-Wide Energy Corridors in Arizona, showing focus of Arizona Solar Working Group in making recommendations to the USFS and BLM.

Flying High in Arizona

While there’s a lot to learn from conservation tools like GIS mapping and migration linkage design studies, it’s an amazing experience to see it all from the air. This past February I had the opportunity to join members of the Working Group on an overflight tour sponsored by Lighthawk and volunteer pilot Will Worthington.

We explored routes north and west of Phoenix to look at possible alternative alignments for a “corridor of concern” and saw the rivers, mountains, and lakes that define that area. Then we headed south over a big swath of Renewable Energy Development Areas (REDAs), identified through RDEP as areas likely to be low-conflict for solar energy development but in need of transmission capacity to stimulate development. Finally we visited the area southwest of the city where wildlife corridors connect rugged mountain ranges that are ringed by river corridors, alfalfa fields, and millenia of human development.

It is no easy challenge to thread a new transmission line into and across this existing patchwork of human and wild spaces. Nonetheless, it’s a challenge that Defenders is glad to work on solving so that our wildlife heritage is protected even as we develop and transmit our valuable renewable resources.


The author joined members of the Arizona Solar Working Group on a Lighthawk overflight tour of potential options for energy corridors and solar development in Maricopa County west of Phoenix on a beautiful February day.

Eliza Cava, Policy Analyst, Renewable Energy & Wildlife

2 Responses to “Long Lines, Smart Lines: Planning Wildlife-Friendly Corridors for Renewable Energy Transmission”

  1. happysunskimmer@yahoo.com

    In the end, I keep thinking that human beings have this “like God” image of themselves, and therefore no body’s safety is more important than our own. Yet we are pretty dispicable when you look at what we really want to do. Destroy other animals “for us”–”We” should always have whatever “we” want–no matter the cost to anything else in the world.

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