The desert has secrets, and it doesn’t give them up freely. This patch of desert I’m camped on east of Joshua Tree National Park seems a quiet bit of desolation, a few scraggly shrubs separated widely with non-descript gravel between them. A few aging beer cans, a few tracks across the landscape left by off-road vehicles. The surroundings mostly seem to contain wind, and cold sun, and silence. Not much to write home about, a person might think.
That person would be wrong.
I can understand why they might reach that conclusion. When I first started falling in love with the deserts, I rushed past places like this to get to the interesting stuff: the tall column cacti in Arizona, the Joshua trees, the red-rock slot canyons.
It took me a while to realize just what I was speeding past. I don’t mean to diss the scenic wonders and grand botanical oddities; they still call to me, and I answer as often as I can. But I don’t need oddities nearby to have my mind blown by the desert. The commonplace will do that just fine.
Today is cold and bright. I sit in the shade of an ironwood tree. Ironwood, Olneya tesota, is a sturdy tree in the legume family. Native to the Sonoran Desert of California, Arizona and Mexico, it’s best known for its incredibly dense, bittersweet-chocolate-colored heartwood, often carved into small sculptures for the tourist trade. Of all the woody plants native to North America only Southern Florida’s leadwood tree has heavier heartwood. The wood is, in the words of Phillips and Comus’ A Natural History of the Sonoran Desert, “rich in toxic chemicals and essentially non-biodegradable.” When an ironwood tree dies only three things are likely to eat its wood. The first is termites, which often completely devour branches up to two inches thick where the heartwood has not yet developed. The other two are fire and wind-blown grit. Firewood-sized chunks found in desert washes have been carbon-dated at 1,600 years old. A standing snag may, after its death, provide valuable habitat for a thousand years.
But my back is to the ironwood. I’m not looking at the ironwood. I’m looking at a scraggly creosote clump about eight feet away. It’s rooted in a mound of soil somewhere between six inches and a foot above the surrounding gravel, and about twenty feet from the nearest creosote. It’s a plain vanilla Larrea tridentata, with nothing to distinguish it from thousands of roughly similar Larreas within my line of sight:
Creosote bushes can live for astoundingly long times. About 65 miles northwest of this little shrub, botanist Frank Vasek determined the age of a large clonal ring of creosote at about 11,700 years. He took the diameter of the clump and divided that by the rate at which a creosote clump expands per year, and later confirmed his calculations through carbon dating of pieces of sub-fossil wood in the clump.
I suddenly wonder how old this little plant is. My patch of desert turns out to have cell coverage, so I fire up my phone and look up Vasek’s paper. Vasek used a complex annual growth increment of between .73 and .82 millimeters to determine his giant creosote clone’s age. I round that up to a millimeter a year to make it easier to do the calculations in my head, then round the number of millimeters in an inch down to 25 from the actual 25.4. That works out to 300 years of growth for a clump to reach a foot across at the base — and my roundings have made that quite conservative, possibly by as much as 20 percent.
I have a tape measure in my Jeep. The width of this little clump at its “crown” — a counterintuitive piece of botanical jargon that means “where the stems come out of the soil” — is about 49 inches. Rounding down to four feet in order to be even more conservative would make this unprepossessing little plant about 1,200 years old.
Which would mean that this plant germinated at around the same time that Charlemagne ruled as Holy Roman Emperor, the Vikings were getting medieval on the population of the British Isles and the Tang Dynasty exacted tolls from travelers on the Silk Road. More locally, the Ancestral Puebloan people were building complex cities across the Southwest. When 15th century Europeans first landed on the islands off North America this plant was already about 700 years old.
This plant is likely more than ten times older than any human has ever gotten, and it’s one of dozens of similar size in the immediate vicinity of my campsite. I get up, startled, and walk around the desert, looking at the creosote bushes with new eyes. Even the smallest and youngest of them here is older than I am, likely far older. Each of them secures its mound of desert soil, enriched by leaf litter over centuries, and inhabited by burrowers from beetles to ground squirrels to tortoises and larger animals:
There are people who would look at this place with its tire tracks, its century’s accumulation of discarded drink containers and the low hum of the interstate three miles south, and dismiss it as worthless — or at least not worth preserving for its own sake. The desert doesn’t give up its secrets freely. You have to sit and watch the desert, and consider what it does tell you, and draw the resulting conclusions.
If the 1,200-year-old creosote where I sat were a redwood tree in a park it would have a plaque nearby, and travelers would come for miles to gaze at it reverently. If it were a coast live oak it would have died of immense old age almost a thousand years ago. If this creosote bush were a tree of like age and people came to cut it down for some industrial project, photos of it would flood the Internet with outraged commentary about our species’ soullessness, and people would line up to be arrested in order to protect it. But it’s a creosote bush, not a giant sequoia, and so it sits here in obscurity, scraping by in dry years like this one and putting out flushes of growth in the wet. If we manage not to uproot it it may still be doing so when all memory of our fleeting civilization has been forever lost.
