September 09, 2010

Desert Solar is Not Renewable Energy

Posted In endangered species & public lands issues & water use & wildlife | By Chris Clarke

As the reality of human-generated climate change grows more obvious and more dire, the campaign to replace our outmoded fossil-fuel-based power generating infrastructure with carbon-neutral alternatives has literally gained ground. Development of solar, wind, biomass and geothermal energy is now a Federal priority. This development, unthinkable just a few years ago, is long overdue.

There’s a right way and a wrong way to do just about everything, however. In the deserts of the American Southwest, most of the large-scale developments on the drawing board have been proposed for public lands, the bulk of those lands previously undeveloped.

Advocates of solar and wind energy development in fragile wildlands often refer to their projects as “renewable energy” development. In the strictest possible sense, the term is accurate: solar power will be abundant as long as the sun shines, and wind will blow across the landscape for about as long. But expand the scope of the discussion a bit and the validity of the term “renewable energy” becomes more doubtful. The energy transformed into electric power may be renewable, but what of the other impacts the power generating stations may have? In desert wildlands especially, development of massive industrial power generating facilities involves damage to the landscape that may take centuries, or millennia, to heal — if it ever does.

If energy company interests proposed cutting down redwoods for biomass conversion, or filling Yosemite Valley with a reservoir in order to generate hydroelectric power, most environmentally concerned people would scoff derisively. The redwoods would certainly grow back, and snowmelt would almost certainly recharge the Yosemite reservoir each year, but few people would limit their assessment of the projects’ “renewable” nature to the specific sources of energy harnessed. Most people would demand that the assessment of the “renewable” nature of the energy project address the nature of the habitats destroyed in order to install the power generating capacity — the old-growth redwood forest, the meadows and sheer rock walls along the Merced River — and the continuing damage to those ecosystems from those projects’ daily operations. We would ask how long it would take for those old-growth redwoods to grow back. We would ask how long it would take, once the Yosemite Dam was eventually removed, for the Valley floor’s ecosystem to regain its grandeur. And we would likely ask ourselves whether a forest 3,000 years in the making, or a valley four times that old at a minimum, were really worth losing for a few extra megawatts.

In the Bureau of Land Management’s California Desert District, just the handful of solar and wind energy project proposals that have been “fast-tracked” — chosen by the Obama administration for accelerated permitting and regulatory approval — would destroy just under 59,000 acres of publicly owned desert wildlands in the Mojave and Colorado deserts. All told, that’s more acreage than is occupied by the city of Lancaster, California. Sprawly Palm Springs occupies only a few dozen acres more. That’s a huge amount of land. Even more would be affected by the new transmission lines the projects would require. And that’s just the fast-tracked projects. Overall in California, the BLM is examining more than 350,000 acres of public land for solar energy development — an area larger than Los Angeles slated for possible habitat destruction in the name of “renewable energy.” Many more hundreds of thousands of acres are being studied in other Western states.

Let’s take a look at some of the aspects of those landscapes that this “renewable” gold rush would damage.

Desert aquifers

Fifteen thousand years ago the climate in Western North America was much different. The California deserts were far wetter; freshwater lakes filled many of the desert’s basins. Water from those lakes, and from the relatively greater runoff and snowmelt from the desert’s fringing mountains, pooled in large aquifers in the deep alluvial soil of the valleys. Most of the great pluvial lakes in the southern part of the desert dried up by about 7,500 years ago, but the aquifers they had left behind remain to this day, water tables sometimes several hundred feet beneath the desert valley surface. One such “fossil water” aquifer, beneath the Amargosa Valley, feeds the renowned springs at Ash Meadows, Nevada, home to the endangered Devil’s Hole pupfish. 

Annual recharge of these aquifers — the amount of water present-day precipitation adds to the total — is quite limited. In the Ivanpah Valley, for instance, astride the California-Nevada line south of Las Vegas, the total annual recharge of that valley’s aquifer amounts to an average of 800 acre-feet a year, according to one estimate. This water comes almost entirely from precipitation falling on the nearby Clark, New York, Ivanpah and Spring ranges. Eight hundred acre-feet sounds like a lot of water. However, the Ivanpah Valley groundwater basin spans more than 400,000 acres. Eight hundred acre-feet of water would raise the water table on an aquifer that size by about half a millimeter.

At that rate of annual recharge, it would take thousands of years to fill the Ivanpah Valley’s aquifer. Most aquifers throughout the desert, aside from those recharged by more well-watered mountains such as the Sierra Nevada and Transverse Ranges, are recharged at similarly slow rates. Desert groundwater from these aquifers is thus best considered a nonrenewable resource.

Artesian springs supplied by these fossil aquifers provide a crucial source of water without which wildlife would suffer. In places where humans have developed the desert, these aquifers are chronically overdrafted: settlements, agricultural irrigation, livestock watering, mining, resort development, and even golf courses all add to the demand on this precious and limited resource.

Whether they are photovoltaic or concentrating thermal in design, industrial solar facilities depend on regular cleaning in order to run at peak efficiency. Even a thin layer of dust on PV panels or mirrors can cut output by a considerable amount. Though research continues into dust-repellant coatings and dry cleaning methods, getting rid of dust means hosing down the relevant pieces of equipment. And in most of the desert, unless the facility is on the Colorado River or an aqueduct therefrom, that water will come up out of a well, adding to the demand on already overdrafted groundwater. Concentrating solar thermal facilities may use water either to drive steam turbines or for cooling, or both. Though engineering advances in concentrating thermal solar technology will likely make the installations far more water-efficient, the amount of water current designs use may be considerable. A plant proposed for the Amargosa Valley by the Solar Millennium corporation would have required 20 percent of that valley’s groundwater. Even the Ivanpah Solar Electric Generating Station, which would use air-cooling techniques to increase water efficiency, is expected to consume at least 100 acre-feet of water each year — an eighth of the annual water budget in the Ivanpah Valley.

If production of industrial-scale solar electricity requires such massive use of a nonrenewable resource, calling the result “renewable energy” seems deceptive.

Old-Growth Desert Vegetation

Visitors to the desert often assume that the wizened-looking large plants there are immensely old. As it happens, many of the most prominent desert plants — outside of the altitudinal range of the piñon-juniper forest, at least — have surprisingly short lifespans. Joshua trees and saguaros are good examples, with average lifespans below 150 years. Ocotillos, one of the more notable large woody plants in the Colorado Desert, endure for about the same length of time.

Desert shrubs, however, often outlive their larger tree companions by a considerable margin. In a 1995 study of woody plants in the Grand Canyon in which landscapes documented in 19th century photos were rephotographed, researchers found that a wide range of desert shrub species reached ages of more than a century. These included catclaw acacia (Acacia greggii); bursage (Ambrosia dumosa); fourwing saltbush and shadscale (Atriplex canescens and A. confertifolia); the cacti Echinocactus polycephalus, Opuntia acanthocarpa, O. basilaris, and O. erinacea; Ephedra; desert thorn (Lycium andersonii); Yucca angustissima; and, a bit surprisingly, the bunchgrass big galleta (Pleuraphis rigida).

A few desert shrubs have lifespans more properly measured in millennia rather than centuries. The best-known of these is the creosote bush, Larrea tridentata. Creosote stems put out side shoots every so often, expanding the plant’s width. As a creosote bush gains in width and the center of the plant eventually succumbs to old age, the shrub becomes a ring of stems and foliage. By measuring the ring’s width and dividing by the annual growth rate, the age of the ring can be determined. King Clone, a creosote ring near Landers with an average diameter of 45 feet, is estimated to be approximately 11,700 years old — placing its germination back in the last pluvial period, when freshwater lakes dotted the desert. 

Another long-lived, slow-growing species, the Mojave yucca (Yucca schidigera), also forms clonal rings. Estimates of the growth rate of Mojave yucca rings vary widely, but it’s relatively safe to conjecture that many such rings exceed 2,000 years in age. Clumps of Mojave yucca with a probable age of 1,000 years are widespread throughout the species’ range.

To be thorough, any discussion of slow-growing desert life must at least mention cryptobiotic soil crusts. These obscure communities of cyanobacteria, mosses, lichen and fungi stabilize soils, fix nitrogen that can then be used by other desert life, and slow runoff of rain and snowmelt. Cryptobiotic crusts are extremely fragile: a stray footstep can break a centuries-old crust, making the soil beneath it vulnerable to erosion by wind and water. Even a slight disturbance in a cryptobiotic crust can take many years to heal. A film of cyanobacteria can recolonize a damaged area within a decade, but the full complement of lichens and mosses may take as long as three centuries to regain its former vitality. It’s worth noting that burial by wind-driven soil is a major threat to cryptobiotic crusts. Bulldozing a swath of desert landscape for industrial energy generation may well cause a swath of continual downwind damage to such crusts, compounding over time as more crust dies and releases the soil beneath it.

Vegetative communities

As an old-growth redwood forest is more than a collection of large trees, so the old-growth desert is more than a collection of shrubs. The broad alluvial fans and plains so tempting to the alternative energy developers are often the home of plant communities that may have taken a staggeringly long time to develop.

At elevations too high or latitudes too cold for creosote to thrive, the unassuming shrub blackbrush (Coleogyne ramossissima) will often cover huge areas in an almost unbroken mantle. These thick stands of Coleogyne are unprepossessing, even uninteresting to the average traveler. They feed wildlife with their seeds and provide nurse-plant shelter for other desert plants, Joshua trees a prime example, and as far as even most desert aficionados are concerned, that is the extent of their interest. 

In 1987, Robert H. Webb, John W. Steiger, and Raymond M. Turner published the results of a study of disturbed areas west of Death Valley. Some of those areas had been disturbed by human activity in the late 19th century, some by debris flows in the last few thousand years, and some by debris flows of Pleistocene age. They determined the rate at which desert plants recolonize disturbed areas. They found that Coleogyne is very slow to revegetate areas from which it had been stripped.

Webb, Steiger and Turner found that blackbrush took as long as “tens of thousands of years” — their words — to revegetate up to 20 percent cover in the areas they studied. Other studies have reaffirmed their findings. The consensus is that the thick, uniform stands of blackbrush so prevalent in the high deserts probably took from 5,000-10,000 years to develop.

Individual blackbrush plants may live as long as 400 years. They grow slowly, and “recruitment” — successful reproduction with offspring surviving to maturity — is rare. Biologists who’ve studied the species have suggested that blackbrush reproduces in “pulses,” its seedlings surviving best in years with heavy early spring rains. Those conditions may well have been more prevalent toward the end of the last pluvial, when — if current thinking is correct — at least some of the current stands of blackbrush got their start. As Webb, Steiger and Turner said it: “Time span for [vegetative] recovery [of blackbrush stands] may be longer than past periods of climatic and geomorphic stability.” Some of the blackbrush stands in our deserts have been developing since there were standing lakes in the Mojave with sabertooth cats and ground sloths drinking out of them. Their replacement under current climatic conditions may take even longer.

That’s if those communities come back at all. Desert ecologists famously refer to the still-visible tank tracks left more than half a century ago by the US Army, training under General Patton during World War II. The Army’s wartime impact on the desert extended beyond making tracks. A few miles northwest of Needles at Arrowhead Junction, the military established Camp Ibis — part of the Desert Training Center — in 1942. The camp was decommissioned two years later. Building the camp involved blading large swathes of creosote-Mojave yucca vegetation for an airfield, building footprints and a network of roads. Though all structures were removed in 1944, the extent of the blading is still clearly visible in current satellite photos. Native plants have colonized much of the cleared area, but those plants are very different from the ones removed. Despite abundant creosote and Mojave yucca surrounding the camp and providing a source of seeds for revegetation, the cleared areas are carpeted mainly in burro weed (Ambrosia dumosa), which may inhibit the germination of other plants by outcompeting them for soil moisture. It may be that once disturbed or destroyed, desert landscapes in areas such as the former Camp Ibis will never regain their original ecological composition.


Our deserts are irrigated by water that fell thousands of years ago. Their slopes are covered in vegetative assemblages that have been developing for a span of time far longer than recorded human history, and some of the individual plants in them are almost that old — older than the rightly venerated ancient redwoods; older, some of them, than the oldest bristlecone pines. Once altered, those plant communities may never return to their original state even under optimal conditions. If the desert’s aquifers and vegetative communities are forever changed, the animal wildlife that has evolved dependence on local springs, plant habitat and edible vegetation — desert tortoises, bighorn sheep, and a raft of other vulnerable species — will suffer.

Losing a few thousand acres of old-growth desert would be a shame, yet hundreds of thousands of acres in the California desert are being studied as possible alternative energy sites. Given the permanent damage to an ancient, irreplaceable ecosystem that would result from industrial energy development in desert wildlands, it’s time we stopped calling such development “renewable energy.”