Recognizing the Patterns
Since we’ve been doing it for a long time, humans are adept at pattern recognition. This ability to make sense of seemingly random blotches and dots has been crucial to our survival and success as a species. For instance, the back pattern of a venomous rattlesnake—even when partially obscured by brush next to a trail—is readily recognized. Likewise, First Nation desert-dwellers, gazing down from a rock outcrop onto the sere plain below, can intuit the presence of shallow groundwater based on the colors and textures of plants that require a modicum of moisture.
Scientists speak of “noise” in their data, random fluctuations that obscure meaningful information. Noise impedes their ability to tease out relationships and patterns. For anyone—writer, detective, scientist—wishing to draw seemingly disparate threads together, it requires training and attention to detail. Unrelated internal monologues and other sources of noise must be stilled, lest pertinent signals be swamped. Sometimes, we encounter patterns unfamiliar to us and the spark of recognition ignites slowly, if at all. However, with careful observation, reflection, and a bit of luck these patterns may become clear.
1. The day after Thanksgiving 2009, southeastern Arizona. As I head westward from Sonoita toward the town of Patagonia, my eyes are drawn toward a vaguely checkerboard pattern on distant hills. It takes only several moments to decipher the pattern, for I’ve noted similar ones before in other locations. Areas of amber dead grass abut squares of darker vegetation, mainly oaks. This juxtaposition results from what bio-geographers term “aspect”—the direction that a hill slope faces. In this land of little rain, any moisture that does fall is swiftly evaporated on slopes that face south or west, resulting in a dry site capable of growing only bunchgrasses. Conversely, the east- and north-facing slopes, shielded somewhat from the relentless borderland sun, retain enough moisture to support oaks with waxy or leathery leaves designed to minimize water loss.
My destination is Santa Gertrudis Lane, which is situated along the Santa Cruz River, about twenty miles north of the border town of Nogales. Here, a combination of native hackberry trees and planted pyracantha bushes furnish berries for a species of bird that has eluded me for just shy of a quarter-century. My nemesis bird is the Rufous-backed Robin, a species that breeds in Mexico, yet has the odd habit of migrating north for the winter. Over the years, I’ve stalked them in locations ranging from Palm Springs, California, southeast across the breadth of Arizona, to the town of Douglas, which lies a long stone’s throw from the New Mexico state line. Despite these many excursions, I’ve nothing to show for it, save for a handful of desiccated salmon-colored hackberries and a pocketful of achingly blue desert sky.
I first noted this aspect checkerboard pattern one April in central California near San Luis Reservoir. There, areas of lush, green annual grass lay cheek-to-jowl with spent, drying, straw-colored grass. The scene prompted me to scrawl a mental sticky note:
To: Authors of ecological-themed textbooks
Subject: In April, a photograph of this site is worth a thousand words.
At my pyracantha bush stakeout, a stiff breeze causes a constant progression of clouds to scuttle by from the southwest. The wind’s not a good sign. Stroboscopic shadows and the constant swaying of limbs are going to make it hard to detect the furtive movements of this notoriously skulky songbird.
At least an hour passed, and I began to lose focus. Funny how similar all my robin stakeouts have been. Lots of time to study hackberry, its lower trunk containing a random, splotchy, 3-D appearance, like a bad drywall texture job. Higher up, its warty limbs branching off in complex, dendritic patterns.
Other birders came and went during the afternoon. Long story made short: late that afternoon, I returned to my car—without my trophy bird.
2. Late October 2012. Chetco River, southwestern Oregon. With school back in session, the campground is deserted, our only company being salmon splashing in the river and a vine maple’s scarlet pyrotechnics framed by our camper’s dinette window. Sue and I are on our first camping trip following the death of our beloved 14-year-old terrier, Gypsy. Her absence requires a retooling of our pre-departure checklist, throwing a monkey wrench into old rituals. We’ve lost our companion who used to sit alongside us at the breakfast table, intent on our cutting small strips of turkey bacon to share with her. While on the road, the rear of the king cab and center console—once her throne—now sit vacant.
Following breakfast, we set out to hike the Alfred Loeb Redwood Nature Trail, which leads to the northernmost stand of coastal redwoods in the world. Just beyond the parking lot, I stop to admire the craftsmanship of a flagstone walkway—doing a double-take when I realize that it’s merely fractured asphalt pavement, the gaps between each “stone” now colonized by moss.
I’m reminded that nature, too, is an artist. The moss-edged slabs mimic a series of repeating patterns: arctic ice polygons, six-sided columns of basalt, desert arroyos—their beds a cracked, dry-clay mosaic. That this pavement I’m now studying has been reduced to somewhat similar-sized, yet unique, chunks suggests that the mechanism involved could be described in mathematical terms—a kind of endlessly repeating pi that pauses at different locations of the sequence. I wish my brother Larry, a math teacher, was here to break it down for me.
3. February 18, 2013. Rucker Canyon, Chiricahua Mountains, southeastern Arizona. In late fall, I came across a paper by Alexander Wetmore entitled “The Thick-billed Parrot in Southern Arizona.” Published in the January 1935 issue of The Condor, it furnished details on a handful of sightings of this bird in the Grand Canyon State, including an astounding 1000-1500 parrots that spent the winter of 1917-18 in Rucker Canyon.
Rucker Canyon lies not too far from our winter home in Palominas, Arizona. So, on a mid-February day, Sue, our new dog Zevon, and I set out for Rucker.
For many people, the mental image of a desert is that of the Sonoran. Because this desert is warmer and at a lower elevation than the Chihuahuan, it supports saguaro cactus and palm trees. In addition, the Sonoran Desert is famous for its golf courses, where verdant, irrigated putting greens often occur alongside sun-blasted volcanic black rock. Whereas our house in a river valley of the Chihuahuan Desert lies at an elevation of 4,300 feet; mountains that tower over the straw-colored grasslands and leafless mesquite are often snow-capped. Scattered yuccas add a splash of green, but the landscape is suspended in a brown and lifeless senescence, owing to winter’s cold.
Thick-billed Parrots—emerald green, with scarlet forehead, eyebrow, and shoulder patches—still breed in the western Sierra Madre Mountains of Mexico. Although the species feeds mainly on seeds of various kinds of pines, it is also known to eat fruit and juniper berries and was observed feeding on acorns during the winter of 1917.
Many of the pines used for food by this species produce cones that require two years to mature. Also, during drought years, trees may produce no cones at all. This irregular cone production is the chief factor in the Thick-billed Parrot’s nomadic behavior. While making plans to visit Rucker Canyon, I came across another paper that gave information on additional sightings in the Chiricahuas in 1898, 1900, 1902, 1904, 1906, 1920, 1922, 1935, and 1938. Although I expected to see some loose correlation between the two-year cycle of pine cone production and the bird’s appearance in Arizona, I was surprised to see that two-thirds of the sightings conformed to this pattern.
As a biologist, I wanted to get a look at the complex vegetation patterns of this biological crossroads, one that contains elements of the Sierra Madre, Rocky Mountains, and the Chihuahuan and Sonoran Deserts. The pines in the Chiricahuas have been decimated by recent fires that include the Horseshoe 2 Fire in 2011 that burned 70% of the mountain range. I was eager to assess the range’s carrying capacity, its ability to again harbor flocks of Thick-billed Parrots. Meanwhile, the writer in me sought to experience the canyon’s ambiance, to steep myself in the parrots’ raucous echoes.
Their echoes aren’t as faint as one might think. Although 1938 was the last time a truly wild Thick-billed Parrot was seen in Arizona, eighty-eight of them were re-introduced into the Chiricahuas between 1986 and 1993. The program to return these parrots to Arizona skies began serendipitously when U.S. customs officials found themselves with twenty-nine wild adult parrots that had been confiscated from smugglers. But the parrots weren’t able to survive drought, habitat changes, parrot wasting disease, and the Northern Goshawk’s fondness for them as prey, so the reintroduction effort was discontinued.
Crossing the boundary into Coronado National Forest, we encounter snow on the road, a hold-over from last week’s storm. Small and easily crossed, the patch of snow nevertheless serves as a reminder of the Thick-billeds’ cold-hardiness. Although parrots are associated with hot, steamy jungles, this species was commonly seen foraging in the snow in the Chiricahuas from 1986-93.
The road veers away from the shaded, north-facing hillside, and we burst into bright sunshine, fording Rucker Creek on a broad apron of concrete. At Camp Rucker, I survey the scene: looming rocky cliffs above a flat meadow, punctuated here and there by tall, stately oaks, their presence imparting a vaguely African savanna flavor.
Continuing onward, we eat lunch at a spot with a commanding view of a meadow that slopes gently to the south, ringed by scattered small pines, oaks, and pockets of brush. Behind us rise the snow-capped Chiricahuas, their massive bulk capable of blocking cold north winds. The hot sun streaming through the windshield suggests that this could be an ideal site for wintering parrots, were it not for the legions of dead, burnt pines that cloaked the hillsides.
Straining against his leash, Zevon leads us down the dusty jeep track through the pines. My eyes, drawn to a massive Arizona madrone, scan to detect the bright scarlet berries favored by many wintering birds. If this parrot has been known to eat skanky juniper berries, why not madrone? I speculate. The tree has few berries, probably due to the ongoing Arizona drought. My gaze then shifts to the bark of the tree’s lower trunk. Furrowed and cracked, it’s more akin to the bark of alligator juniper than the smooth, nude, red-orange branches overhead. The bark’s fractured, mosaic-like pattern reminds me of… Oh, I remember. The flagstone asphalt pattern along the Chetco River—and the photo that I forgot to send to my brother for his input.
I circle the tree slowly, peering upward. Nothing. We reach the end of the trail and turn around, making our way back to the vehicle. A down-canyon wind sets pine needles to murmuring, masking any parrot echoes that might remain.
Following our visit to Rucker Canyon, I e-mailed Larry a photo of the pattern created by the asphalt walkway. Just before sending, I decided to append the photo of the madrone bark. Within minutes, I was viewing his response:
Fascinating. What we have here is a tessellation of aperiodic tilings of
mainly triangular, quadrilateral and pentagonal shapes. Fun to look at
to decipher the pattern although I do not believe there is a systematic
pattern making it aperiodic.
The bark also forms a tessellation. Tessellations were never my forte so
I’m calling in an expert on tessellations. Suzette, can you help us out
My brother and I need your help. Larry
My brother’s jargon-filled response made little sense to me, validating my long-held assertion that he held a near-monopoly within our family on an aptitude for math passed down from our father, an electrical engineer. However, by patiently consulting several dictionaries, I was able to penetrate his world. To paraphrase, a tessellation is composed of tiles, which take on a geometric shape. Some tiles can be of the same shape, whereas aperiodic tilings—owing to their dissimilar shapes—cannot form a repeating pattern. Following a childhood where we shared many interests, the life paths chosen by my brother and me diverged, so I always relish finding some common ground.
4. July 2007. Pilot Creek, Trinity County, California. While doing fieldwork—inspecting and collecting data on streams and culverts—co-worker Alicia Perez and I encounter a jumble of fallen tree limbs beneath a stand of old-growth Douglas-fir. This obstruction slows our progress, forcing us to pick our way carefully over the debris. The limbs have been on the ground for some time, evidenced by their lack of bark and needles. They are an arresting sight, their bright russet surfaces gleaming, as if burnished by some unseen hand. Inspecting a limb more closely, I note that bark beetles have etched intricate designs through the darkened patina of cambium into pale-colored wood.
I share the find with Alicia and we study several limbs, transfixed.
“Anyone who’s split firewood or bought poor-quality lumber has seen similar designs,” I exclaim. “But this combination of pale etchings against a dark-colored background is unique. I’ve never seen anything like it.”
Alicia nods. “It’s a kind of art,” she responds.
We discuss how the Sequoia Park Zoo in Eureka recently outfitted Bill the chimp with brush and palette and later sold his paintings. I’d also heard of enterprising African villagers encouraging elephants to paint.
“Maybe bark beetle engravings could be the next big thing,” I suggest. “I’m going to take some limbs, maybe frame them.”
Later, on the drive back to the office, something occurs to me. Noise can take many forms. Before today, the bark beetles’ signal had always been swamped, because of the lack of contrast, pale color on pale background.
5. February 4, 2011. San Pedro River, southeastern Arizona. The digital thermometer at our house—located a mere three miles from Mexico—registers zero degrees.
“It’s possible that it’s even colder,” I remark to Sue. “Who knows if it even registers sub-zero temperatures?”
Later that day, in the midst of what proved to be a record-setting cold snap, we decide to venture out for a walk. Our short drive to the river is punctuated with oohs and aahs as we note frozen vegetation. Old-growth prickly pear cactii—towering above shed and fence just yesterday—now lie flaccid, slumped across roof and barbed wire like an aged, vanquished boxer.
Clad in our warmest winter clothing, we crunch our way down to the river. The edges of beaver ponds—the water’s velocity slowed by stair-stepping dams—lie frozen. Protruding blades of amber grass serve as vertices for jagged, crystalline ice patterns. The sun, slanting down through leafless cottonwood trees, is mesmerizing, glinting off the ice. This, I sputter to Sue through numb lips, is an aspect of the borderland Arizona winter unlikely to be touted by the local Chamber of Commerce.
Again, during February 2013, a cold snap struck and we experienced three consecutive nights of six-degree temperatures. Who knew that southern Arizona could get so cold? Old timers knew—that it didn’t used to get this cold.
Climate change has altered the old patterns: a scarcity of cold temperatures and snow in the Northeast during winter, resulting in forsythia blooming at Christmas. A tornado season in the Midwest and South that now begins in January rather than March or April. Record-setting cold in the Southwest.
6. June 4, 2013. AP newspaper article: “Trade Winds Drop, and Hawaii Gets Muggy.” Our memories can play tricks on us. Because of this, I maintain a healthy level of skepticism whenever folks share with me claims such as, “it’s never been this hot” or “the snows have never come so early.” The wary scientist in me responds—usually inaudibly—“Show me the data.” Hawaii’s climate appeals to many of us, subtropical warmth, but lacking the oppressive heat and humidity of the tropics. The trade winds are an essential part of Hawaii’s salubrious climate, as these cooling breezes also dissipate humidity. Over the past four decades, though, some residents have complained that the trades are no longer dependable, resulting in less precipitation, higher temperatures and humidity, and more smog—locally termed “vog” because its particulate matter comes from volcanic activity.
University of Hawaii at Manoa meteorologist Pao-shin Chu suggested that several graduate students look into the situation. Using wind data from four airports and four ocean buoys, the researchers confirmed a 28% drop in the trade winds since the early 1970s. Their results were published in the Fall 2012 Journal of Geophysical Research.
The contention that rainfall has also been reduced is also true. Average rainfall per decade—measured since 1951 at Hilo International Airport on the Big Island of Hawaii—has also diminished during the past 40 years. Precipitation during the period 2002-2012 is 16.2% lower than during the previous four decades. Because trade winds are responsible for bringing moisture-laden air to this remote archipelago, their slackening is considered to be partially responsible for reduced rainfall. Water district managers in Hawaii are alarmed at the prospects of furnishing water to an increasing population during times of decreased rainfall. For this reason, Honolulu’s water utility hired Chu to develop rainfall forecasts for the coming decades.
That the researchers could cite a multi-decade dataset for wind speed and precipitation is but one example of the benefits of standardized, long-term record-keeping. The public perception that the trade winds were reduced was confirmed, rather than being an erroneous memory, distorted by time.
We live in a time of wild climatic oscillations: record-breaking heat and cold and the diminishment of trade winds that are considered a crucial part of global wind circulation patterns. Because extreme temperature events are consistent with climate change models, researchers now favor the term “climate change” over “global warming.” These changes are testing the mettle of farmers, ranchers, water district managers, and others who rely on the predictable passage of seasons with their associated precipitation and winds.
What patterns are emerging to replace the old ones? It would be a stretch to term the new pattern the absence of one. However, at various places around the globe, our memories haven’t failed us. Many of the old patterns have disappeared.