More than half of the Mojave Desert biodiversity "hotspots" identified in a study published this week are under threat from utility-scale renewable energy development and related transmission corridors, with as much as 17 percent of the habitat in those hotspots sitting directly in the footprint of proposed energy and transmission projects.
The study, "Evolutionary Hotspots in the Mojave Desert" by the U.S. Geological Survey's Amy G. Vandergast and 13 co-authors from the USGS and various universities, was published Monday in the journal Diversity. Vandergast and her colleagues examined genetic records of 17 Mojave Desert animal species, calculated the genetic diversity within those species and mapped those parts of the Mojave Desert that were home to the greatest amount of that diversity. Vandergast et al identified 10 "hotspots" of that genetic diversity within the Mojave Desert, which were:
- A: Dunmovin - Coso Junction (CA)
- B: Sierra -Tehachapi Transition (CA)
- C: Antelope Valley - Mojave Desert Transition (CA)
- D: Ord Mountains - Lucerne Valley (CA)
- E: Indio Hills - Little San Bernardino Mountains (CA)
- F: Pluvial Lakes (Bristol/Cadiz/Danby) (CA)
- G: Colorado River Mountains (Mojave/Black Mountains) (CA/NV/AZ)
- H: Sacramento-Detrital Valley (AZ)
- I: Ivanpah Valley (CA/NV)
- J: Virgin Mountains (NV/AZ)
They then overlaid a map of proposed utility-scale solar and wind projects, along with associated transmission corridors, and found that six of the ten identified hotspots overlapped with energy development projects.
High levels of genetic diversity within species are significant in that they can offer a species a greater chance of surviving future ecological challenges such as climate change. Such genetic diversity can result from a range of different conditions in a small area to which members of a species must adapt -- or to use the phrase offered by Vandergast et al, "an ecotone of steep environmental gradients." Such ecotones are usually present where different kinds of habitat butt up against each other: a steep mountainside verging onto an alluvial plain, the edges of grasslands, the banks of a desert river such as the Colorado, and so forth.
Genetic diversity within a species can also be heightened in places where two formerly separated populations of that species meet. By way of example: one of the species studied, the Mojave desert tortoise, is especially genetically diverse in its Ivanpah Valley population, and Vandergast et al hypothesize that this may be due to the dry lakes on the valley floor offering an historic barrier to gene flow when they had water in them.
Other species of the 17 examined by the team ranged from two species of ground spider to the desert bighorn sheep, and included four species of rodent, two snakes, a toad, and a number of lizards both rare and common. Most of the animals studied are considered endemic to the Mojave Desert -- they live there and nowhere else.
As the habitat these animals live in in the desert's hotspots seems to be driving increased genetic diversity, fragmenting that habitat may well be a threat to that diversity's future -- and to the ability of those species to adapt to an increasingly changing desert. Vandergast's team found that proposed desert utility-scale renewable energy projects would occupy between 2,563 and 3,209 square kilometers of the hotspots they identified for the 17 animal species they studied. (That's 990-1,240 square miles, an area twice to three times the size of Los Angeles.) Transmission corridors through hotspot areas ate up another 8,503-10,733 square kilometers, which works out to between 3,283 and 4,144 square miles -- roughly equivalent to somewhere between San Luis Obispo and Los Angeles counties in extent. Combine both footprints and energy development could displace as much as 17 percent of the total land area of those biodiversity hotspots.
The researchers note that their work isn't the be-all and end-all of biodiversity studies in the Mojave, especially noting that there's a lot of potential in the northern part of the Mojave for as-yet undiscovered hotspots, in places where energy development also proceeds apace:
The lack of coverage in the northern Mojave represents a significant data gap. Because hotspots tend to occur at ecotones, the northern transition between the Mojave and Great Basin may also retain high genetic diversity. This region may be particularly important if climate change results in northward range shifts for some species.
In our race to develop utility scale renewable energy at all costs, in other words, we may not know what kind of biodiversity we're sacrificing until it's too late.