Recently, I wrote about plans for the new 690 megawatt (MW) Gemini solar farm that is to be built in the Nevada desert and touched on the fact that many are concerned with the threat this poses to the endangered Desert Tortoise.
Currently in Nevada, a 15 MW community solar farm owned by the Valley Electric Association (VEA) has been studying the effects that the farm has on the desert tortoise along with native desert plant species, which the tortoise needs for survival.
For the construction of the solar farm, VEA worked closely with the U.S. Fish and Wildlife Service (USFWS) and Bombard Renewable Energy to design a system that would have the lowest impact on the tortoise and its sensitive habitat.
Together they designed a fence with special tortoise gates that are 10 inches wide by 7 inches high and spaced them out every 260ft. Jennifer Wilkening is a biologist from the U.S. Fish and Wildlife Service that oversees the project’s habitat protection plan. The fences dimensions were determined by “how far tortoises have been known to walk along a fence line in the past, looking for an opening,” said Wilkening.
For the desert plants, which are vital for survival, the researchers planted 90 nursery seedlings of cover plants and flora within the solar site and watered them for three months. The juvenile tortoises are especially dependent on the plants to hide from would-be predators and for shade from the sun.
Creosote plants provide much of the cover the tortoises need and last winter the plants continued to grow on-site inside the fence, and outside they did not as reported by the University of Nevada, Soil and Water Scientist, Dale Devitt. Here he talks about the teams’ research in his VEA annual report:
It appears the solar facility is altering the microclimate and surface hydrology in ways that are currently extremely beneficial to both creosote and bursage, compared to the unaltered habitat that surrounds the facility. Creosote and bursage provide the majority of cover for the smaller animal life.
To accommodate for the plants, the fixed-tilt solar PV panels were placed with the lower edge 18 inches higher off the ground than current industry standards. This allows for more vegetation to grow, which according to Wilkening are the primary food sources for tortoises.
In an interview with PV Magazine, Devitt spoke more about the construction of the panels and the effect it can have on nature:
Although it is still early in the study, the preliminary results demonstrate that conditions inside the solar facility are less stressful on the plants, with both creosote and bursage staying active year-round. We believe the results demonstrate that a paradigm shift is needed in terms of how solar facilities are installed. Installations should be designed not only from an engineering perspective but from a biological perspective as well.
To help accommodate the tortoises and other wildlife at the site, the VEA created a temporary habitat for tortoises during the construction process. They designed it with one road that runs through the site to access the equipment for maintenance, allowing the other areas for natural vegetation. There was also no grading of the site during construction, which left the plants’ root systems intact.
Similar studies have been done at the 550 MW Topaz project in California, by First Solar. The research on vegetation showed “greater [percentage of] live cover, less bare ground, and higher species diversity” than on surrounding lands. They attributed this to greater soil moisture, “the array fields provide a shading effect similar to an orchard, allowing the growing season to be extended”.
The desert tortoises are protected by the Endangered Species Act. These studies show that rather than solar fields proving a threat to the tortoises, they could, instead help to replenish the population. By working together with successful organizations who already have projects in place, the Gemini solar farm can provide further research and help support these beautiful creatures. At the same time, solar panels reduce the carbon emissions that the entire planet so desperately needs at this time.
