by Emil Morhardt
The massive development of wind and solar generating facilities in California’s Mojave Desert puts California way out in front of the rest of the US in generation of renewable electricity, but at the same time the development drastically alters the desert ecosystem. Installation of photovoltaic arrays seems to require grading the land flat, removing all existing vegetation, and since there will be nothing to eat, all of the animals as well. To those who haven’t travelled this wild desert during a verdant spring—something that happens only every few years—it might seem barren. But I’ve camped out in the middle of it many times in the spring when it is lush, covered with desert flowers, and alive with birds and other animals; to me it is the epitome of virgin wilderness. (My wife and I even wrote a book about it and took a lot of plant pictures…see reference below.) So, one question to ask is whether or not any of that desert life will recover under the solar panels.
A research project addressing a small part of this question has been under way in the Mojave since 2011, and while not ready for scientific publication, is turning up some interesting results. Tanner et al. (2014) constructed isolated solar panel simulators—angled sheets that shaded the ground and deflected rain—and have been checking to see if two of the tiny daisies that are often abundant after rains thrive under the panels. In 2011 when they started the experiment there were 850 Barstow woolly sunflowers (Eriophyllum mohavense) and 454 Wallace’s woolly daisies (Eriophyllum wallacei) per square meter!
In 2012 there were almost none. (Rainfall makes all the difference in this ecosystem.) Last year there was enough rain to get some germination, so some early results are now available; the panels block out 85% of the solar radiation under them, and it is 11°C cooler, so the researchers certainly expected differences under and away from the panels. They now know that the panels not only reduced emergence of the Wallace’s daisies, more of them died before flowering. Also, there weren’t as many other plant species under the panels, and the total density of plants was lower. They don’t say anything about how much soil moisture there was under the panels compared to their control areas, but since this is probably the most important variable I’m sure they’re monitoring it. Also, as any roadside botanist knows, it’s the runoff from the edges of the road that often produce the only flowers, so comparing the runoff zone from the panels with the area under them should be interesting.
These are early results, but it is clear that the extreme year-to-year climatic variation in this environment is going to make it difficult to get definitive data, and it is going to take a long time. Meanwhile, many of the proposed solar panel facilities have already been constructed, so it will be possible to do similar research under the real thing. Will the operators let the desert vegetation grow under the panels? A drive through some of these facilities in the Antelope Valley the other day suggests not always, and the only vegetation in evidence where it was allowed was the aggressively invasive tumbleweed–not too surprising since all of the native vegetation had been graded away and the ground heavily disturbed. I hope that research on how to protect the desert biota under the panels becomes a standard condition of licensing.
Tanner, K., Moore, K, and Pavlik, B. 2014. Measuring Impacts of Solar Development on Desert Plants. Fremontia 42: 15-16 (no online version found)
Morhardt, Sia, and Morhardt, Emil. 2004. California Desert Flowers; An Introduction to Families, Genera, and Species. University of California Press. 284 pages.