The Trees That May Survive Humanity

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Bristlecone pines have the look of survivors, not conquerors. Fittingly, they found fame during the Cold War, when atomic tests were taking place not far off, in the Nevada desert. Bristlecones are post-apocalyptic trees, sci-fi trees. Photograph by John Chiara for The New Yorker

Alex Ross mainly writes about music, but when he sets his sights on other important topics his musicality illuminates in a powerful way:

The Past and the Future of the Earth’s Oldest Trees

Bristlecone pines have survived various catastrophes over the millennia, and they may survive humanity.

About forty-five hundred years ago, not long after the completion of the Great Pyramid at Giza, a seed of Pinus longaeva, the Great Basin bristlecone pine, landed on a steep slope in what are now known as the White Mountains, in eastern California. The seed may have travelled there on a gust of wind, its flight aided by a winglike attachment to the nut. Or it could have been planted by a bird known as the Clark’s nutcracker, which likes to hide pine seeds in caches; nutcrackers have phenomenal spatial memory and can recall thousands of such caches. This seed, however, lay undisturbed. On a moist day in fall, or in the wake of melting snows in spring, a seedling appeared above ground—a stubby one-inch stem with a tuft of bright-green shoots.

Most seedlings die within a year; the mortality rate is more than ninety-nine per cent. The survivors are sometimes seen growing in the shadow of a fallen tree. The landscape of the Ancient Bristlecone Pine Forest, as this area of the White Mountains is called, is littered with fragments of dead trees—trunks, limbs, roots, and smaller chunks. Pinus longaeva grows exclusively in subalpine regions of the Great Basin, which stretches from the eastern slopes of the Sierra Nevada to the Wasatch Range, in Utah. Conditions are generally too arid for the dead wood to rot; instead, it erodes, sanded down like rock. The remnants may harbor nutrients and fungi that help new trees grow. Bristlecones rise from the bones of their ancestors—a city within a cemetery.

Coast redwoods and giant sequoias, California’s gargantuan world-record-holding trees, can grow fifty feet or more in their first twenty years. Bristlecones rise agonizingly slowly. After four or five years, the seedling on the steep slope would have been just a few inches higher, sprouting needles in place of the embryonic shoots. The needles are a deep green, tough, resinous, and closely bunched, in groups of five. On a mature tree, they live for fifty years or more. Decades may have passed before the tree was human height, and decades more before it resembled a conventional pine. Bristlecone saplings grow straight up, with relatively sparse foliage, looking like undernourished Christmas trees. After a few hundred years—by which time the Old Kingdom of Egypt had fallen—it was probably forty or fifty feet in height.

Many tree species live for hundreds of years. A smaller but not inconsiderable number, including the sequoias and certain yews, oaks, cypresses, and junipers, survive for thousands. Once a bristlecone has established itself in the unforgiving conditions of the White Mountains, it can last almost indefinitely. The trees tend to grow some distance from one another, so fires almost never destroy an entire stand. Because only a few other plant species can handle the dry, cold climate, the bristlecones face little competition. Unlike most plants, they tolerate dolomite soil, which is composed of a chalky type of limestone that is heavily alkaline and low in nutrients. As for insect threats, bristlecone wood is so dense that mountain-pine beetles and other pests can rarely burrow their way into it.

Empires rose and fell; wars raged; people were enslaved and freed; and the tree from 2500 B.C. continued its implacable slow-motion existence, adding about two-hundredths of an inch to the diameter of its trunk each year. Minute changes in the tree-ring record make bristlecones an exceptionally useful source of data about changing conditions on earth. When rains are heavier than normal, the rings widen. When volcanic eruptions cause global cooling, frost rings make the anomaly visible. The precision of these records means that bristlecones have periodically butted into other disciplines: geology, archeology, climatology. In the nineteen-sixties and seventies, the trees contributed to the upending of the canonical theory that Bronze Age civilization had spread westward from Egypt and the Near East. Bristlecones have also affected modern political discourse: the famous “hockey stick graph,” which two decades ago raised awareness of human-driven global warming, relied on bristlecone data.

As the millennia go by, bristlecones become contorted and wraithlike. The main stem, or leader, dies back. Entire branches, even the trunk itself, become fossils. At first glance, the tree may look dead. Such is the case of the forty-five-hundred-year-old tree that clings to life near the tourist path that now runs through the Ancient Bristlecone Pine Forest. Spears of dead wood jut into the air. The trunk is a marbled hulk stripped of bark, like driftwood thrown from a vanished ocean. A ribbon of live bark runs up one side, funnelling water and nutrients to clumps of green needles high above. All told, the tree is an unprepossessing specimen; most people march past it without giving it a second glance. When I sat by the tree for an hour last July, the only visitor who took any notice of it was a dog named Dougie, who briefly sniffed the trunk and then darted away.

In 1957, Edmund Schulman, a researcher from the Laboratory of Tree-Ring Research, in Tucson, determined that this eccentric senior was older than any other tree on earth which had been dated. He named it Methuselah. The next year, when the United States Forest Service established the Ancient Bristlecone Pine Forest, Methuselah bore an identifying marker. The sign was soon removed, however, because tourists were extracting souvenirs. The tree’s location is now known only to scientists, forest rangers, and a few enthusiasts. This anonymity is just as well, since there are almost certainly Great Basin bristlecones that are yet older. A nearby tree appears to have been born about three hundred years earlier. Even more ancient trees are rumored to exist elsewhere in the Whites.

What is most astonishing about Pinus longaeva is not the age of any single organism but the collective oldness and otherness of its entire community. No two super-elderly trees look alike, to the point where they have acquired the characteristics of individuals. Trees are prone to anthropomorphism; we project our dreams and our anxieties onto them. Bristlecones have been called elders, sentinels, sages. The possibility that climate change will cause their extinction has inspired a spate of alarmed news stories, although tree scientists tend to discount the idea that the bristlecones are in immediate danger. They have survived any number of catastrophes in the past; they may survive humanity…

Read the whole article here.

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