In a world facing a shifting climate, rising global population and prolonged droughts, maintaining ecosystems through proper land management is of critical importance. It’s also a task that a recent Colorado State University study found possible through installing solar panels on grasslands.
Originally published in Environmental Research Letters May 29, collaborative research between CSU and Cornell University found evidence that solar panels installed on semi-arid grasslands improve local soil moisture content and reducing water stress. Both of which increased local plant growth by up to 20% compared to open fields.
The study was a collaborative effort between CSU University Distinguished Professor of biology Alan Knapp and Matthew Sturchio, who received his Ph.D. in ecology from CSU in April 2024.
“We have been interested in how ground-mounted solar arrays will impact the semi-arid grasslands of Colorado,” Knapp said in an email-based interview. “This is a pressing issue because the state of Colorado has a clean energy mandate to transition to 100% net-zero emissions by 2050. Solar arrays require a lot of land area and abandoned agricultural lands. Degraded lands, as well as the dry, low productivity grassland of the eastern plains of Colorado are ideal areas for solar infrastructure.”
Photovoltaics, as Knapp explained, refers to the process of converting sunlight into electricity through semi-conductors housed in solar panels. When formulating their working hypothesis, the pair sought to measure the panels’ impact on sensitive grassland ecosystems, which offer agricultural and economic benefits while the local biome remains strong.
“Grasslands harbor tremendous biodiversity, store significant carbon and support the livelihood of millions of people globally via pastoral (and) grazing use,” the publication reads.
To test in the field, the researchers partnered with Jack’s Solar Garden, located in Longmont, Colorado. The 24-acre facility allowed for real-time results to be captured across the study’s four yearlong timespan.
Uniquely, each year during the research process brought a breadth of rainfall variability, much to the benefit of Knapp and Sturchio.
“Over those four years, we got pretty lucky,” Sturchio said. “We actually ended up seeing three of those four years have drastically different rainfall inputs. So one year was a dry year, one year was almost exactly what the average for the last 30 years is, and then one year was not a record, but it was the second wettest year in recorded history in Longmont.”
This variety of weather patterns allowed the team to test multiple hypotheses over their four year window, with results varying depending on the rainfall amount that year.
“We found that in years when rainfall is below average, plant growth was indeed improved within solar arrays compared to outside,” Knapp said. “But in wet years, there was a modest decrease in plant growth, probably due to the shading effect of the solar panels.”
To measure their findings, the duo utilized several research tools, ranging from the newest technologies to more traditional, time-tested methods. One main tool utilized was infrared gas detectors, capable of measuring wavelengths of infrared energy.
“You can control this chamber that you put on the leaf and slowly ramp down, and you can see how the plant responds to different changes in light,” Sturchio said. “And that tells us a lot about how a plant responds to, obviously, growing in the shade versus growing in the sun, and if it has any sort of acclimation to those new growing conditions.”
The researchers also took by-hand measurements on a diurnal schedule. Data points were taken by hand tracking the exchange of water through the stomata of plants below the solar panels. While tracking slightly differs every year during the study’s four-year span, 80 dirunal measurements were taken in 2022.
“Over those four years, we got pretty lucky. We actually ended up seeing three of those four years have drastically different rainfall inputs. So one year was a dry year, one year was almost exactly what the average for the last 30 years is, and then one year was not a record, but it was the second-wettest year in recorded history in Longmont.” –Matthew Sturchio, Cornell University postdoctoral research associate
The geographic region of each solar panel was divided into four quadrants: the east edge, west edge, directly underneath the panels and between each row. While regionally close, every space offered Sturchio and Knapp different findings in their measurements.
“Those micro-sites all vary very drastically based on their environmental conditions,” Sturchio said. “So one of the edges ends up getting sunlight in the morning, (and) the other edge gets sunlight in the afternoon.”
While the study’s results varied depending on the precipitation levels from the recorded calendar year, a general trend with positive ecological and economic benefits emerged.
“In a dry year, because you have this rainfall concentration at panel edges and you have this reduced evapotranspiration, which is the combination of evaporation from soils and transpiration from plants that’s reduced under solar arrays, that combination ends up getting you about 20% of an increase in overall productivity, so more forage available for grazers, whether that’s sheep or cattle,” Sturchio said.
Further solar energy production is continuing to skyrocket in Colorado, so further development and understanding of ecological impact on grasslands is critical. Knapp and Sturchio are currently hoping to install solar panels in the short grass prairie biome present at CSU’s Semi-arid Grassland Research Center to further research photovoltaic’s effect in different grassland conditions.
“This gives us a really good ability to test more hypotheses about grasslands, not only in Colorado, but in this entire semi-arid and arid grassland ecosystem, which dominates most of the dryland west,” Sturchio said.
Reach Katie Fisher at science@collegian.com or on social media @RMCollegian.
