"Life is a desert of shifting sand dunes. Unpredictable. Erratic. Harmony changes into dissonance, the immediate outlives the profound, esoteric becomes cliched. And vice versa." — Ella Leya

Picture in your mind 100 square miles of sand dunes filling the floor of the Coachella Valley. Episodic floodwaters eroding sand out of the uplifted igneous granitic batholith of the San Bernardino Mountains, flowing down the channels of the Whitewater River and Mission Creek, spreading across the western edge of the valley.

Some sand-bearing floods would have occurred every 5-10 years, but perhaps once a century the floods and the volume of sand they carried would have been tremendous. Once the waters ebbed and the sand dried, powerful winds coursing down the San Gorgonio pass, winds squeezed between the San Bernardino Mountains to the north and San Jacinto Mountains to the south, would push piles of sand east and southeast. The sand sorting, first by moving water and then by wind results in extremely uniform grain sizes, typically less than 0.5 mm and greater than 0.125 mm.

When those 100-year floods occurred, the sands moving west were so deep they would engulf the Indio Hills, including Edom Hill, making early visitors think they were mountains of aeolian sand. Before the winds would finally lose the strength needed to push sand, the sands would eventually reach where the cities of Indio and La Quinta exist today. Except there were no cities then. The ever-changing sand dune landscape created a barrier, then repelling every attempt of human colonization. The Cahuilla people lived along the mountain edges, well south or north of the relentlessly moving, shape-shifting bolus of sand. Eventually, when non-indians first came here to live, they too set up communities that hugged the southern mountains.

Most sand dunes form from the erosion of sandstone, primarily tiny crystals of quartz that take on the hue of the rock from which they came. Pinks and beige, and sometimes starkly red sand dunes are the result of erosion from sandstones of those colors. Sometimes the sandstone source material can be quite far from where the sands are deposited, and dunes began to form. As the Colorado River eroded away the sandstones to create the Grand Canyon, those sands were deposited far and wide when the river jumped its banks during flood stages. That is how the Algodones Dunes in Imperial County were formed, and how the vast dune field of the Gran Desierto in northwest Sonora Mexico formed. There are a couple of sites in North America where sand dunes form from gypsum crystals blowing off dry lake beds. White Sands National Park is just such a place, with sands so white they nearly hurt your eyes to look at them. At least as rare as gypsum dunes are dune sands that started as solid granite. Usually so hard and resistant to mere water flows, there is another force at work here, the San Andreas fault fracturing the granitic batholith as the North American and Pacific tectonic blocks grind against each other. The resulting sand mirrors the granitic minerals, quartz, feldspar, and mica. Of those three, feldspar is by far the softest, and once free of the protective quartz and mica matrix, it eventually erodes to clay-sized particles and blows away as dust. What is left, the quartz and mica sand grains, have a salt and pepper appearance when viewed close-up, and white to off-white when viewed from afar.

When viewed from afar, sand dunes look beautiful but lifeless. Of course, if you walked away with that assumption, you would have been simply wrong (though not wrong about them being beautiful!). Still, for life to become established on sand dunes, that life had to overcome a mobile surface and abrasive, scouring sand every time the wind blows more than about 20 miles/hour, something that happens quite often. No easy task. If you need to be rooted in one place, the moving sand is either trying to bury you or erode at your base and is buffeting you with miniature shards of quartz crystals. Looking from afar, it is then not surprising that on the active dunes, plants can be sparse at best. However, when you take a closer look, there are plants growing in wind-protected nooks and crannies created by the ever-moving dunes. Sometimes the plants were established before the dune was created and though the moving sand engulfed the plant, but the plant was able to continue grow and keep its crown above the sand surface. This is especially true of honey mesquite dunes, and sometimes creosote bushes and other woody shrubs. A surprising feature of sand dunes is that those uniform sized dune sands hold on to rainwater much better than coarser alluvial sands, so if you can get established on a dune, you have access to a more dependable water source than plants on alluvial fans or rocky hillsides.

And there are animals that have evolved to be able to exploit the sand dune habitats as well. Fringe-toed lizards are a model of the capacity of evolution to solve the challenges their habitats have created. Around the world where sand dunes form, there are lizards who live there. Different species, even different families, dune lizards all share one or more features that enable to thrive in this habitat that is inhospitable to those who have not proceeded along this evolutionary path. Smooth scales (keeping the sand from getting underneath scales), countersunk jaws (allowing the lizards the ability to dive into the sand without forcing their mouths open), extended or multiple eyelids (to keep sand from abrading their eyes), small nostrils (to keep sands from entering their lungs), and enlarged sales on their toes (to provide traction on a loose sand surface, and making them the fastest vertebrate on the dunes to avoid predators). Unrelated lizards around the world all sharing one or more of these features. If Charles Darwin had visited sand dunes around the world rather than coastlines and oceanic islands, I can imagine his “Aha!” moment would have come to him much sooner. The only problem in being superably adapted to a unique and challenging environment is that once you get there, you are stuck. All those features give you an edge if you are on a sand dune; off the dune and you are at a disadvantage. So, in many ways sand dunes are like terrestrial islands, and as a result each is inhabited by creatures that are often found nowhere else on earth. There are even some animals that have perhaps not gone “all in” when it comes to their evolution to a sand dune life. They end up living on the more stabilized areas surrounding the more active dunes. An example is the flat-tailed horned lizard. They do not like coarse alluvial sand, or rocky habitats (desert horned lizards occupy that habitat), nor are they found on those active dunes (where fringe-toed lizards are kings and queens), rather they live on the more stable, more vegetated dune flats.

With the hubris that so often characterizes our species, here in the Coachella Valley people were not content with leaving those sand dunes alone. First, rather than skirting around the edge of the dunes, from 1872-1887 the Southern Pacific Railroad built a railroad line right through the middle of the 100 square miles of dunes. Of course, the dunes responded by shifting sand right over the train tracks, so the railroad planted dense rows of non-native tamarisk trees on both sides of their tracks. This act alone severed the dunes, cutting off the dunes’ access to new, replenishing sand. Dunes down-wind from the railroad tracks become “sand starved” and the habitat quality declined. A few decades later the construction of the US 99 highway in 1925, paralleling the railroad, further severed the dunes from their sand sources. US 99 later became Interstate 10. As those communities along the mountain edge filled up, there were incremental forays of agriculture and development into that sea of aeolian sand. By the 1970s that 100 square mile dune system had been sliced and diced, fragmented into about 10% of its original extent. By 1980 it was down to 5%. 

In 1980, a group of scientists and concerned citizens, led by University of California Riverside professor, Dr. Wilbur Mayhew, successfully petitioned the State of California and the Federal government to protect the Coachella Valley fringe-toed lizard. The problem then — and the problem we still face — is that those critical pathways have mostly been severed that would have allowed for new sand to replenish habitats as the strong west and northwest winds push the sand east and southeast.

Putting a fence around a dynamic, moving pile of sand, does not protect the homes of dozens of species, unless there is a connection allowing new sand into the system. On the other hand, allowing floods and then winds to bring new sands in to replenish these habitats can put critical transportation arteries and people’s property at risk. There are no easy solutions. Harmony changes into dissonance, the immediate outlives the profound ...

Nullius in verba

Go outside, tip your hat to a chuckwalla (and a cactus), and be safe.