Research at one of the largest solar facilities in the Mojave Desert indicates that a rare annual plant is not only surviving, but thriving under a construction approach designed to preserve desert soils and seed banks. Researchers monitoring the Gemini Solar Project northeast of Las Vegas documented a sharp increase in the number and size of triangle milk vetch installations two years after the panel’s installation compared to pre-construction conditions.
The work, led by ecologist Tiffany Pereira of the Desert Research Institute (DRI), is detailed in a study published in Frontiers in Ecology and Evolution in late November 2025. The team revisited plots within the Gemini Solar Project footprint that had been surveyed before construction began in 2018, focusing on the rare triangular milkvetch, a member of the pea family that qualifies for listing under the US Endangered Species Act.
In 2018, surveyors documented 12 individual triangle milk vetch plants on the project site prior to construction activities. When Pereira and colleagues returned in 2024, they counted 93 plants within the same project area, indicating that the soil seed bank survived the disturbance and that the species recovered numerically after the installation of the solar panels.
“We were curious to see what impact the construction would have on the seed bank,” Pereira said. “What we found was that not only did the seed bank survive, but the plant emerged. And these were big plants, they were bigger in every metric we measured – width, height, number of flowers and fruits, leaf length – than the plants we measured on site. That was really cool and surprising.”
To separate the effects of construction from natural variability in rainfall, the team compared plants growing within the Gemini facility to individuals at a nearby, undisturbed reference site. By examining two populations experiencing the same regional weather, the researchers were able to attribute differences in plant performance to the presence of solar infrastructure and associated changes in microclimate, rather than solely to annual precipitation shifts.
The Gemini Solar Project differs from many large-scale installations in the arid Southwest because builders did not simply “civilize and level” the site by scraping away vegetation and topsoil before installing panels. Conventional cutting and grading methods clear the soil, remove shrubs and biological soil crusts, and destroy the upper soil layers that contain long-lived seeds, making natural recovery difficult or impossible even when rainfall is favorable.
Instead, Gemini adopted a lower-impact construction strategy, seeking to preserve existing desert surfaces and biological resources where possible. The study notes that this approach appears to have preserved the triangular milkvetch seed bank over much of the area, allowing the species to emerge post-construction and take advantage of altered soil moisture patterns under and around the panel arrays.
Threecorner milkvetch is considered rare in its limited range and is categorized as Critically Endangered and fully protected by Nevada. The U.S. Bureau of Land Management lists it as a species of special status. As an annual, the plant spends most of its life cycle as a dormant seed in the soil, emerging above the ground only in years when rain patterns provide sufficient moisture for germination, growth and reproduction.
Because of this life history strategy, populations may appear to disappear in dry years and then reappear in large numbers when wetter conditions return. The researchers suggest that the higher growth rates observed at Gemini may be related to the way the solar installation affects groundwater retention. Sensors and field observations indicate that the soils within the project area retain moisture for longer after storms than the soils at the undisturbed comparison location.
“Subsequent years of monitoring will help us explain this,” Pereira said, “but soil moisture levels on Gemini are higher after rainstorms. The water stays in the soil longer after rainstorms, so it takes longer to dry out. The plants may just be sucking up that extra water.”
Although triangle milkvetch individuals within the project boundary were on average larger than those outside, the team recorded only a single plant growing directly in the shaded area under a solar panel. Most individuals occurred in the open strips of ground between panel rows, suggesting that the species may have specific light or microhabitat requirements that are not met under continuous panel cover.
This pattern highlights potential tradeoffs even with more sustainable construction practices. Although careful surface protection can ensure the survival of seed banks for rare plants, the range footprint still reduces the amount of fully suitable habitat. The study recommends additional experiments, including controlled germination trials, to test whether shade or other physical aspects of the setup limit seedling emergence and survival under panels.
Pereira emphasizes that the 2024 study represents only one year of post-construction monitoring and cautions against drawing long-term conclusions from a single season. Under desert conditions, annual plant populations can fluctuate orders of magnitude depending on the timing and intensity of rainfall. Thus, several years of data will be needed to confirm whether Gemini continues to support robust triangle milk vetch populations.
“Our number one goal for land managers is always avoidance,” she said. “When it comes to rare plant habitat, avoid them if possible, and then these alternative construction methods can be used to preserve habitat in areas where it cannot be avoided.” The Gemini results, she added, show that less disruptive approaches can offer a compromise where complete avoidance is not realistic.
The findings fuel a broader debate about how to expand renewable energy infrastructure in the American Southwest without erasing the landscapes that define the region. Many conservationists have warned that the rapid expansion of utility-scale solar energy threatens fragile desert ecosystems, especially where foliage and slope remove vegetation, topsoil and cryptobiotic crusts over hundreds or thousands of hectares.
By showing that at least one rare species can survive and even thrive under a large solar array built with seed bank-friendly methods, the Gemini study provides a more hopeful example. It suggests that with advance planning, careful surface management and ongoing monitoring, land managers can reap the benefits of fossil fuel-free energy while maintaining the ecological function and some of the biodiversity value of an intact desert habitat.
“Our desert species are amazing,” Pereira said. “These seed banks can withstand a lot: they remain in the ground for years, waiting for the right conditions to germinate, and now we know they can even survive using softer construction methods. With a little ingenuity, we can address both the environmental and renewable energy issues. These things can work together.”
Research report: Rare milkvetch (Astragalus) persistence at a utility-scale solar facility in the Mojave Desert
