Can desert tortoises and solar arrays co-exist?

One solar energy facility in southern Nevada is helping to answer that question

Solar energy planners in Nye County, Nevada hope to alleviate any impacts to habitat for the endangered desert tortoise, like the one shown above near Ash Meadows National Wildlife Refuge. Credit: Dana Wilson/BLM

Solar energy planners in Nye County, Nevada hope to alleviate any impacts to habitat for the endangered desert tortoise, like the one shown above near Ash Meadows National Wildlife Refuge. Credit: Dana Wilson/BLM


By Dan Balduini and Jennifer Wilkening
July 19, 2019

Motorists driving into or out of Pahrump on Nevada Route 160 pass by it every day. On the east side of the highway north of town, about a mile beyond the Calvada Meadows Airport, drivers might notice a shining array of community solar panels.

The new, large-scale solar energy facility project near Pahrump, Nye County, Nevada. Credit: Bombard Renewable Energy

The new, large-scale solar energy facility project near Pahrump, Nye County, Nevada. Credit: Bombard Renewable Energy

What they see is an 80-acre solar site on East Simkins Road which provides electricity to homes in Nye County, Nevada. Solar power facilities are now common sights in the Mojave Desert. However, the U.S. Fish and Wildlife Service chose to make this one a bit different.

Large scale solar energy facilities provide relatively clean energy and create jobs and access to electricity in rural communities. However, substantial tracts of land are typically needed to capture the sun’s energy, and the environmental footprint of such projects can be considerable.

Continued development of solar facilities on previously undisturbed land could threaten natural ecosystems through habitat loss and fragmentation, leading to reduced biodiversity and ecosystem resilience.

Similar to other eco-regions characterized by harsh environmental conditions, the Mojave is considered a hotspot for threatened and endangered species. The Mojave Desert tortoise, for example, has been listed as threatened under the Endangered Species Act since 1990.

One of many desert tortoises living in the vicinity of the solar project. Credit: USFWS

One of many desert tortoises living in the vicinity of the solar project. Credit: USFWS

So when another solar array was being planned in Nye County, planners designed it in a new way, hoping to alleviate impacts to tortoises and other species under a habitat conservation plan issued by the Service.

The desert tortoise is a long-lived, plant-eating reptile with a relatively low reproductive rate. Desert tortoises construct burrows and maintain their body temperature by spending most of their lives within them to avoid extreme temperatures. The area near the solar array is home to several Mojave Desert tortoises.

The 51,480 photovoltaic panels at the Mojave site are on metal piers and follow the natural undulations of the land on which they were installed.

The panels are fixed with a 30-degree tilt, and their bottom leading edges are 18 inches higher off of the ground than the industry standard, allowing the vegetation to return to its natural state.

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U.S. Fish and Wildlife Service biologists, Nye County and Valley Electric Association officials tour the solar project near Pahrump, Nevada. Credit: USFWS

Solar arrays are further apart than usual so that more light can reach the ground and potentially break up the appearance of an artificial lake that may attract water birds to the site.

Ground disturbance was kept to a minimum, as the only grading done on the site was for the construction of an access road through the center of the facility.

The permanent fence surrounding the facility includes openings around the bottom perimeter so desert tortoises (and other wildlife) can enter, exit and occupy the site during operation of the facility.

Also, operating guidelines were established to minimize risks to tortoises and other wildlife inside the facility, such as the use of small utility vehicles rather than trucks, low maximum speed limits, and desert tortoise awareness training for workers.

Openings like the one shown here are located at several points along the project's perimeter fence to allow the area's desert tortoises to forage inside the project. Credit: USFWS

Openings like the one shown here are located at several points along the project's perimeter fence to allow the area's desert tortoises to forage inside the project. Credit: USFWS

“The habitat conservation plan for the project ensures that the tortoises have access to suitable habitat, both inside and outside of the property,” said Service wildlife biologist Jennifer Wilkening. “Natural vegetation grows well on the site, and the chain-link fencing around the project has openings along its base to provide the tortoises with access to that vegetation.”

“The habitat conservation plan for the project ensures that the tortoises have access to suitable habitat, both inside and outside of the property,” says Service wildlife biologist Jennifer Wilkening. Credit: USFWS

“The habitat conservation plan for the project ensures that the tortoises have access to suitable habitat, both inside and outside of the property,” says Service wildlife biologist Jennifer Wilkening. Credit: USFWS

With tracking transmitters fitted, biologists can track the tortoises’ movements to determine whether the installation impedes their foraging or burrowing activities. Wilkening said that tracking data and site surveys show that the reptiles do enter and exit the facility during their active periods.

Research and monitoring studies are underway to investigate the ability of native plants to persist under solar panels and how well the project area functions as habitat for wildlife.

Data will be used to evaluate how solar panels influence surface temperature and precipitation distribution, and how vegetation may respond to varying environmental conditions.

For example, favorable microclimates could be created since solar panels shade desert surfaces and provide additional moisture, and this could result in enhanced plant growth and survival for vegetation communities underneath panels.

Additional studies include avian surveys and mortality monitoring, camera trap monitoring of wildlife use at fence openings, testing of herbicides for invasive weeds, and evaluation of habitat restoration techniques.

The facility went online in March 2017 and generates a peak output of 15 megawatts. The project currently serves approximately 2,500 homes with renewable energy, while leaving a relatively small environmental footprint.

On top of that, the “all-you-can-eat” buffet at the solar site appears to be a hit with the local desert tortoises.

Rows of solar panels follow the topography of the site. The natural vegetation remains as a food source for the tortoises living on and near the facility. Credit: USFWS

Rows of solar panels follow the topography of the site. The natural vegetation remains as a food source for the tortoises living on and near the facility. Credit: USFWS


Dan Balduin is the public affairs officer for the Southern Nevada Fish and Wildlife Office located in Las Vegas, Nevada.

Jennifer Wilkening is a senior biologist in the Southern Nevada Fish and Wildlife Ofice.