Great Basin National ParkThousands of feet above the Nevada desert, in a part of Great Basin National Park that tourists rarely see, park ecologist Gretchen Baker neared the top of Mount Washington and raised her binoculars. There just below, sprouting directly from the limestone, grew some of the oldest living things on Earth.
Great Basin bristlecone pines, their dense pale trunks twisted like thick rope by centuries of gusting wind and rain, thrive here in part because so little else does. At altitudes near 11,000 feet along Nevada’s rocky Snake Range there are no grasses, no brush, few pests, no competition. No people to start wildfires. No nearby trees to spread pathogens.
With nothing around to kill them, these ancient beasts are left alone year after year to simply do what they do: store water in needles that can live for decades and pack on the teensiest bit of heft at a time. The wood grows so slowly it gets too dense for beetles or disease to penetrate.
Some individual bristlecones have survived this way since before the pyramids were erected at Giza. That includes Methuselah, in California’s White Mountains, the oldest documented living bristlecone, which, based on tree-ring data, is 4,853 years old.
Scientists have long believed that makes this tree the planet’s oldest single living thing. But that argument grew more complicated this month after a Chilean researcher used unusual techniques to date a tree of a different species, a Patagonian cypress. If correct, his work would make that South American conifer the newest oldest thing.
The claim has tree researchers abuzz but skeptical, at least in part because the cypress, growing in a temperate rainforest, appears to live such a different life than a bristlecone. Despite their longevity both the bristlecones and the interloper are now facing questions about how well they’ll navigate the coming decades.
An old rival
Patagonian cypresses, also known as alerces, are native to Chile and Argentina and have long been recognized as the world’s second longest-lived tree species. The previous record-setting alerce was identified in the early 1990s by counting tree rings on a cut stump; it was more than 3,600 years old. (The oldest known giant sequoia, the third longest-lived species, was identified the same way and lived to 3,266.)
But earlier this month, a story in Science by Gabriel Popkin revealed that environmental scientist Jonathan Barichivich and the researcher who first identified that old alerce had been studying another tree in a Chilean national park. The researchers used a T-shaped increment borer to drill in and remove a core sample from the moss-draped cypress. The boring device couldn’t reach the center of the tree, which is more than a dozen feet in diameter. But by combining their core sample with tree-ring information from other alerces, and using computer modeling, the pair estimated the tree was roughly 5,400 years old, with an 80 percent chance it was more than 5,000 years old.
The research has not been peer-reviewed yet, but Barichivich has shared his findings at conferences. Nate Stephenson, an emeritus scientist with the U.S. Geological Survey, who has studied giant sequoias for four decades, finds the results interesting, but is withholding judgment until Barichivich publishes a paper detailing his methods. Still, “the prospect is certainly exciting,” Stephenson tells Popkin.
Others, though, are quite skeptical. Peter Brown, founder of Rocky Mountain Tree Ring Research, which gathers information on the world’s oldest trees, says Barichivich’s approach is too novel to make such a bold claim before publication. “There are many assumptions necessary for extrapolating total age from that,” Brown says.
Brown doesn’t doubt the tree is significant. The partial core alone seems to show the tree was at least 2,400 years old, which would put it among the top 10 oldest trees on Brown’s list. But Brown has other reasons to be suspicious. For example, “this new estimated age is over 1,500 years older than the oldest known (alerce) tree to date,” Brown says.
Brown also sees significant differences between the types of environments that tend to support the very oldest trees and the surroundings of the Patagonian cypress. In an isolated, austere landscape, like the snowy, rocky homes of slow-growing bristlecone, trees can just keep on going. Mossy rainforests, on the other hand, are full of life—and threats.
Scientists still argue about why some trees are able to live so long. “My contention is that trees don’t necessarily die from old age like mammals,” Brown says. “Something has to come along and kill them.”
Barichivich understands the skepticism. He says his colleague has found another alerce stump whose tree rings can all be counted and show it to be about 4,100 years old. (That data is also not yet published.) He also argues that tree-ring data suggests alerce actually grow more slowly than bristlecones, meaning their wood is also very dense.
And as part of a recent research team that analyzed the relationship between the world’s longest-lived trees and climate, Barichivich believes the two species’ worlds are similar in the most important ways. The Chilean Coast Range is nothing like the American West, he says, “but there are special conditions here, too.”
His ancient alerce grows on a cloudy south-facing slope, where the annual mean temperature is roughly 45 degrees Fahrenheit. It’s found in a ravine, protected from fire and until recently from humans. Barichivich says his own Chilean grandfather, who worked as a ranger in the park, discovered the tree in the early 1970s and may well have been the first person to touch it.
A common threat
Regardless of which species turns out to be the longevity champ, those who study the world’s oldest trees are united by a common concern for how their favorite species will make it through rough times ahead.
Wildfires worsened by our fossil fuel emissions have wiped out up to 19 percent of California’s giant sequoias in just the last two years.
(Read about how forests are reeling from climate change—but the future isn’t lost.)
While the location of the very oldest bristlecones are kept secret, Barichivich’s Chilean tree now draws lots of tourists, who stomp around its base, potentially damaging roots. Climate change is also drying out the region, which could threaten the tree’s water uptake.
Bristlecones, too, are seeing a changing world. On a cloudless day last July, Gretchen Baker’s pickup lurched up a gravel road so steep it felt at times like it might tumble off the mountain. Anna Schoettle, a plant ecophysiologist with the U.S. Forest Service, bounced around in the back seat. They were here to explain how the ancient pines might weather rising temperatures.
The oldest living sequoias were seedlings more than 3,200 years ago, around the time of the Trojan War. Back then, the oldest bristlecones living today would already have been around for 1,600 years.
One reason for that is the bristlecone’s capacity to handle stress. As soil erosion or root decay and age weaken a bristlecone’s trunk or branches, the entire tree does not die—only the portion under direct stress. Instead, these majestic beings practice “strip barking,” allowing thin bands of living tissue beneath the bark to curl up the tree delivering water from healthy roots. On some bristlecones, as little as 5 percent of what you see may still, in fact, be alive.
“You won’t usually see a super old tree that has bark all the way around it,” Baker says. “It’s just got this one little living part. Whole portions of the tree are now just really artistic-looking dead wood.”
Bristlecones live across a broad altitude range, from about 6,500 feet up to more than 11,000 feet. They have survived all kinds of conditions. The trees are typically spaced far enough apart that even the occasional lightning-sparked fire rarely spreads beyond a few acres.
But as we rounded a corner in Baker’s truck, an image of the planet’s new reality came into focus. We rolled by acre upon acre of burned husks. A hotter, bigger, more powerful fire, fueled in part by a changing climate, had blown through in the last few decades, wiping out many bristlecones.
Warming temperatures, drought, and more explosive fire pose new threats to these ancient trees, but mostly at the lower end of their range. Bristlecones are also susceptible to blister rust, an imported fungus that has killed millions of related trees, including whitebark pines in Yellowstone National Park. So far it has not appeared in the wild in Great Basin bristlecones.
“Blister rust is a threat, absolutely,” says Stanley Kitchen, an emeritus research scientist with the Forest Service. “How big of a threat is something I don’t know. That’s a big question mark for me.”
Baker, Schoettle, and Kitchen worry that bristlecones at that lower edge of their elevation range are likely to have a rough time in coming years.
But “I don’t worry about the direct effects of climate change on the upper half, where it’s most at home,” Kitchen says. “It would take, I think, even more climate change than is projected to make them disappear.”
