"Poets say science takes away from the beauty of the stars — mere globs of gas atoms. I, too, can see the stars on a desert night, and feel them. But do I see less or more?" — Richard Feynman

Water is essential for life on Earth. When water is in short supply, as it is in deserts, life evolves mechanisms to use what water there is as economically as possible. Smaller leaves (palo verde), no leaves (smoke trees), leaves with waxy coatings (creosote bushes), temporary leaves (ocotillo), and scaly bodies (lizards) are all designs for water efficiency.

However, there is one desert plant that thumbs its leafy nose at saving water. Its leaves are enormous and persistent all year round, running their photosynthetic factories, turning carbon into sugars and the building-blocks of life, using gallons and gallons of water, all summer long. If you plotted the natural occurrences of these plants on a map you would define the boundaries of the hottest and driest region in North America, the Colorado Desert. This seemingly enigmatic plant gets away with its frivolous water use because it only exists in those few locations where there is abundant water at or very near the surface. I’m talking about the desert fan palm, (Washingtonia filifera). 

Like nearly all desert plants, the palm’s origins are in the tropics, but rather than adapt to desert aridity, these palms stayed where the ground stays wet. The natural range of desert fan palms extends south, about one third of the way down the Baja California peninsula, to at least Cataviña and near Bahia Los Angeles, east to the Kofa Mountains in western Arizona, and north to the 49 Palms and Mara oases in Joshua Tree National Park. There is no easy explanation as to why they do not extend further into Arizona (they do quite well there now as human-aided transplants), further south in Baja California (there several other palm tree species there that extend all the way down to the cape region), or further west into the coastal regions of southern California (again, they do very well there now as landscape ornamentals). Some have speculated that first humans to occupy this region may have purposefully or accidentally moved the palms to their current distribution, perhaps from refugia farther south. This could have happened. The palm fruits are tasty, sugary morsels that are a treat to eat, but even if it was too cold for the palms in the Mojave Desert, why not trade with other tribes further into Arizona or coastal southern California? 

Where these palms occur they act as a keystone species. The western yellow bat, Lasiurus xanthinus, is most often found roosting in the fronds, or skirts, of this palm, occurring there along with many other bat species that have less restricted distributions. Leaving the palm skirts on the trees provides bat habitat and so free mosquito control. The palm skirts also provide habitat for western screech-owls, barn owls, long-eared owls, and great horned owls, (so free rodent control) as well as habitat for California king snakes, gopher snakes and desert spiny lizards. Despite their name, I’ve also seen granite spiny lizards occupy these palms. The palm fruits provide important fall and winter succor for western blue birds, American robins, and coyotes. Without the palms, some of these species would not as easily venture into the desert aridity. The robins and bluebirds are likely candidates for moving palm seeds between wetlands in the Colorado Desert, and their short intestinal time-lags may be the limit of how far beyond the palms’ core distribution these species could transport palm seeds. The palm skirts provide an apartment-like refuge for many different species, protecting them from the otherwise extreme summer temperatures. These palms can survive most fires (being a monocot, their vascular pathways of water and nutrients are imbedded deep in their trunks and so are protected from all but the most intense fires). However, those fires remove the palm’s skirts, and so those multiple-species apartments are destroyed. It can take many decades, if ever, for new skirts to develop.

Another animal whose life is entwined with palms is the giant palm-borer beetle, Dinapate wrighti. As beetles go, this one does deserve the moniker of being giant, as they can get up to 6-7 cm in length (around 2-3”). Back in the 18^th and 19^th century it was quite fashionable to have a personal insect collection on view in your parlor, especially in upper-class Europe. Having a beetle or butterfly on display that was the rarest, most colorful, or biggest was apparently a status symbol. Knowing this, explorer-naturalists were often on the look-out for such prizes, as they could, if sold in the right marketplace, more than cover the cost of an expedition. One such fellow was exploring the deserts of southern California and captured a Dinapate in a Coachella Valley palm oasis. This beetle is far larger than any other member of the beetle family Bostrichidae, and the fellow found the prize he had hoped to find. As the story goes, he carefully secured a couple specimens and then traveled up into the Mojave Desert (where there were no palms and no Dinapate) and wandered about for a week or more before heading into Los Angeles to sell his beetle. Apparently, he did well, selling it for the equivalent of hundreds of dollars. For the next few years, he periodically retraced his journey back into the Mojave Desert, and only after being sure he was not followed did he venture back into the Coachella Valley palm oases for more beetles. Eventually, others also found this beetle, but the market collapsed and/or the European habit of displaying such treasures fell out of fashion.

These beetles spend up to seven or maybe more years as larvae inside a live palm trunk, munching away at those vascular bundles. Then, they emerge as adults and within a few short days find a mate, lay their eggs in another palm tree, and then die. In relating this story, I sometimes am asked whether we should apply an insecticide to rid these palms of this pesky beetle. The beetle and the palms have lived together for tens of thousands, if not millions of years. Only when a palm tree is otherwise stressed by age or reduced access to water, have I ever seen the beetles contribute to that palm’s demise. So, no, no pesticides are warranted. However, this beetle-palm relationship may provide a clue as to the current palm distribution. Every palm oasis I have visited has giant palm-borer beetles, as evidenced by the quarter-sized exit holes dotting the older trees’ trunks. These beetles are clumsy fliers and only live as adults for a few days. The beetles’ moving large distances to find new palm trees to “attack” is unlikely. Yet, all these small, isolated, palm oases have beetles. One explanation is that, millions of years ago when conditions were much wetter (before the development of deserts as we know them today), perhaps the palms were not restricted to isolated canyons. Perhaps it was wet enough for the palms and the beetles to have a broader, more continuous distribution. What we see today could be just the isolated refugia where the palms and beetles have been able to survive, relicts of a once more tropical climate, where they have been weathering multiple climate shifts and the more “recent” development of our modern deserts.

An excellent place to experience a palm oasis is in Thousand Palms Canyon within the Coachella Valley Preserve. There are at least ten palm oases that trace different branches of the San Andreas earthquake fault system, the faults bringing water to the surface and to the palms. The visitor center in the main oasis was built from palm logs in the 1920s; many of those logs bear the beetles’ exit holes as they emerged as adults. The oases there have a rich human history, beginning with Cahuilla villages, followed by homesteaders (after the Cahuilla were moved to reservations in Palm Springs and at the north end of the Salton Sea), land developers intent on creating yet another golf resort, to the creation of a system of protected lands, a process catalyzed by the Coachella Valley fringe-toed lizard. 

The first homesteader was Al (“Alkali Al”) Thornburg. Alkali Al had been part of the early U.S. military surveys of this region in the 1860-70s. He returned to homestead the Thousand Palms Oasis and lived there until 1906 when Louis Wilhelm rode up in his wagon pulled be a pair of mules. Louis was looking for a permanent water source to establish a ranch. Alkali Al took a liking to the wagon and mules and a trade was made. 

Ultimately Louis’ youngest son, Paul, was given the oasis, and Paul continued to live there until he passed away. Through the years, Paul developed a close relationship with the Cahuilla people living on the Torrez-Martinez Reservation at the north end of the Salton Sea. So close was that relationship, that Paul had apparently been adopted as an “honorary” tribal member. During the 1970s, Paul was being pressured to sell the oasis to the Dart Corporation, intent on turning the entire canyon into a new golf resort. Paul was worried about his oasis being lost and expressed his anxiety to his Cahuilla friends. A Cahuilla elder visited Paul and heard his concerns; the elder then walked around the perimeter of the oasis, chanting as he went. When he had completed his circle of the oasis, the elder went to Paul and told him he had no reason to worry, that now the oasis would be protected forever. Paul eventually did sell the oasis to the Dart Corporation, but soon thereafter The Nature Conservancy purchased the canyon from Dart. The oasis is now protected forever.

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