Some caveats here, before you have the chance to email me a "correction": There are many older "trees" in Europe, some of which have lived for nearly 10,000 years. But those trees are clonal, reproducing asexually over and over again throughout history. The individual trees themselves are usually just a few hundred years old, though they're genetically identical to the collectively ancient trees connected to the same root system.
"The tree we have stumbled across is a unique individual," said Stockholm University graduate student Paul J. Krusic, part of the expedition that found the tree. "It cannot rely on a mother plant, or the ability to split or clone itself, to survive. Cloning is a very effective evolutionary survival strategy. It's cool, but it's not the same. It's not the same as you or I being left alone to our own devices and living for 1,000 years, like this tree."
There are also individual trees estimated to be much older than this particular Bosnian pine (which has been nicknamed Adonis), but those ages are based on size, historical record and presumed growth rate. Individual trees with confirmed ages in the thousands are relatively common in the United States, but the oldest ever found in Europe squeaks in at barely a millennium.
Because Adonis is the type of tree that lays down about one ring each year, it can be aged quite conclusively. Krusic specializes in this method of tree-ring dating, which is called dendrochronology.
He first became interested in this particular Grecian forest when he read an academic thesis on it years ago. Krusic wasn't out looking for the continent's oldest tree — he was on an expedition to use tree dating to learn about historical climate change and other environmental shifts — but he suspected this particular patch of trees in Greece might be worth looking at.
"In the thesis, there were photographs of these amazingly contorted trees," he recalled. "They looked an awful lot like trees I'd seen along the Great Basin in the U.S., which are very old. They lived in almost a similar environment, very rocky, semiarid, so they had all of the hallmarks one would expect for an old tree."
To confirm the age of some of the trees, Krusic and his colleagues from the University of Mainz and the University of Arizona had to extract cores from which to count growth rings. This process doesn't harm the plants — the cores themselves are only around 5 millimeters in diameter — so Adonis isn't in any danger because of their observations. The scientists counted the rings, then compared some of the nearby trees to one another to account for any anomalies (sometimes a ring won't reach all the way around a tree, so the core seems to miss a year, for example).
"We actually didn't reach the center," Krusic said, meaning that some number of the tree's rings were left uncounted. And the core wasn't taken from the base of the tree, so it only shows the rings that formed once the sapling grew to be a certain height.
"So it's definitely older," he said. "We're just reporting the actual ring count."
In addition to Adonis itself, the researchers found more than a dozen surrounding trees that pushed 1,000 years of age. To Krusic, the truly remarkable thing about these trees is that they survived in a relatively busy area. Most of the ancient trees found in the Americas are truly in the middle of nowhere. Adonis sits in a scraggly region only trafficked by sheepherders and hikers en route to more exciting destinations, but it's still just a few miles from areas that have been inhabited for thousands of years. Krusic believes that the trees have survived by adapting to live in an ecosystem no one else wanted — even though civilization hustled and bustled just down the road.
Krusic says the age results for Adonis won't be published in a journal. His expedition is actually focused on the trees that haven't been so lucky. Adonis and its compatriots are surrounded by their fallen comrades — trees that have stayed preserved, felled on the ground for thousands of years thanks to the region's dry air. Krusic and the other researchers will study these time capsules for hints about changes in the region over time.
"That has a story in it. A story about climate change, about human influences," Krusic said. "That's the real story we're working on. This is just something we stumbled upon."