In the middle of summer, when daytime temperatures are often 110 degrees, there is a palpable tension in this shimmering desert landscape, accentuated by the high-pitched trill of small cicadas that cling to the limbs of mesquite. When the sun is at its highest and shade is reduced to its least accessible form, only lizards and ants seem unaffected by the heat. Before the monsoon season empties its heavy clouds, the desert seems to go into hibernation. The plants are rooted in place, slightly shriveled, and must tolerate the sun as best they can. There are few blooms; you may find, beneath a canopy of spines, the small wilted pink flowers of chain-fruit cholla. Most animals have adjusted their activities to night. All the living things await rain.
If you look up “desert” in a dictionary, you will often find that besides describing an arid environment, there is a secondary definition of a place being “lifeless and dull” or a “wasteland.” I can’t help but be irritated by those who would equate the desert with a wasteland. I would argue that the desert is one of the least wasteful environments in the world. Looking out over the desert, I see organisms that have successfully co-evolved to frugally use what limited resources are available. (I’m not including Homo sapiens as one of those frugal organisms. We are a fairly recent invasive species to the deserts of our western hemisphere. How long have people been in the deserts of the American southwest? Probably around 12,000 years. Coincidentally, humans arrived at the same time the mammoth and giant ground sloth disappeared. Or is that a coincidence? Our arrival signaled an accelerated disappearance of animals that had been surviving here for millennia.)
If I were to quickly describe a desert, I would say that it is an environment where evaporation exceeds precipitation. In other words, it is a land that incrementally loses water over a long period of time. Water is necessary for life to exist, of course, and a complex of life exists in the desert.
Not all deserts are equal in their aridity. Here in the United States, our driest, hottest desert is the Mojave which includes well-known Death Valley. There you can find animals and plants specifically adapted for surviving severe desiccating conditions. (Consider the kangaroo rat, which can live its entire life without drinking water. It gets the moisture it needs to survive from seeds it collects for food. It can also slow its metabolism to minimize moisture lost through respiration.)
The Sonoran Desert, where you find Boyce Thompson Arboretum, is one of the wettest deserts in the world. But in this comparatively lush environment, we still plainly see that plants and animals conserve water. Cacti have a protective waxy cuticle. Small leaves of the jojoba and manzanita point upward to avoid direct sunlight. Legume trees have developed pinnate leaf structures for filtering light and creating soft shade. There isn’t a native organism here that doesn’t show evolutionary signs of regional adaptation. It is for us to study and understand the nuances of these adaptations. If we can’t understand them, at least we might be able to appreciate the intermingling patterns of past and present.
At its hottest, with the sun beating down, the desert certainly seems inhospitable and alienating to humans. Only foolish people and naturalists will venture out into this country on a mid-July afternoon. But far from being a wasteland, the desert is a supremely refined biome that functions on a narrow margin. There is very little waste to be found in this environment except for the waste created by its human inhabitants. Think “Las Vegas.”