Tree-ring researchers at the University of Arizona have helped date what they called the oldest tree in Europe — a 1,075-year-old Bosnian pine growing in the mountains of Greece.
To be precise, and to head off arguments with backers of a Welsh yew, a Portuguese olive tree and a Norway spruce, it is the oldest non-clonal European tree whose trunk has been cored and its rings counted and cross-dated.
It joins a Fitzroya in Chile, an Atlas cedar in Morocco, a Huon pine in Tasmania, a Siberian larch in Mongolia and the granddaddy of them all, a bristlecone pine in California, in the roster of ancients on each continent.
All seven continents have tree-ring stories to tell — even, weirdly enough, treeless Antarctica.
North America, specifically the United States, has plenty of champion trees, including the oldest one on the globe — a bristlecone pine more than 5,000 years old.
It also boasts giant sequoias more than 3,000 years old, along with juniper, pine and cypress that have survived a millennium or two.
Most of those discoveries were made by researchers at the University of Arizona’s Laboratory of Tree-Ring Research, the birthplace of the science that uses tree rings to answer questions about sylvan chronology, global climate and even social and political history.
The Andes of Chile and Argentina contain forests of ancient trees known as Fitzroya, also called Patagonian cypress or “alerce” in Spanish. It is the second-oldest tree species.
One dates back 3,645 years. Like most of the champions, Fitzroyas live at high altitude, where slow, steady growth seems to be their key to longevity.
The Bosnian pine dated by UA tree-ringers in 2016 is a relative child at 1,075 years, but it grows in a region where people have been felling trees for homes, ships and fuel for more than 5,000 years, said dendrochronologist Valerie Trouet.
Europe is also home to ancient groves of olive trees whose rings are uncountable; fabled, old trees whose fables can’t be documented; and a Norway pine, part of a communal grove whose roots grew nine millennia ago but whose stem is a 100-year-old youngster.
Somewhere in Asia are trees that are certainly older than the record-holding Siberian larch, whose 750 rings were sampled and counted after it was discovered growing in Mongolia.
One well-documented tale is of a sacred fig in Sri Lanka, the “Jaya Sri Maha Bodhi,” said to be a cutting of a sacred fig from the Indian state of Bihar under which Siddhartha Gautama, the Buddha, sat while achieving enlightenment.
Then there is a giant trunk of a cedar tree found washed up on a beach in Lebanon that dendrochronologist Ramzi Touchan carbon-dated at 6,000 years old.
Touchan also found and dated the African record-holders, also cedars. He found the oldest one in the Atlas Mountains of Morocco. It is 1,025 years old, and he is worried about it. It has been cored by scores of research teams and possibly weakened.
A couple of contenders grow on islands off mainland Australia. A giant kauri tree in New Zealand has never been dated, but claims for it range from 1,250 to 2,500 years. It is a survivor of two waves of deforestation that hit the island when Polynesians and, later, Europeans, arrived.
The oldest documented tree on the continent is a 1,114-year-old Lagarostrobus franklinii, or Huon pine, on the Australian island state of Tasmania.
Nothing bigger than lichens or mosses grows in Antarctica, where four months of total darkness, ice sheets and sub-zero temperatures make it inhospitable to woody plants. But there were times during the Triassic and Permian periods, more than 250 million years ago, when forests grew along its coastline. Scientific explorers have discovered fossil stumps and trunks, their wood long ago “silicified’ or replaced with minerals in water that flowed through.
A NASA/USC/LSU study in 2012 also found leaf wax from the middle Miocene epoch (15 to 20 million years ago) in sediment cores drilled beneath the Ross Ice Shelf.
Why North America?
There are a number of reasons why North America hosts the oldest trees on the globe.
Its deforestation did not begin until the 1700s. It is the birthplace of the science of dendrochronology, with the longest history of tree-ring investigations. It also hosts some long-lived species of trees.
The bristlecone pines of the White Mountains in California are, almost without doubt, the oldest trees in the world, and were discovered almost by accident by dendrochronologist Edmund Schulman in the 1950s, said Malcolm Hughes, a Regents’ professor at UA and former director of the Laboratory of Tree-Ring Research.
Stunted by short growing seasons and twisted by wind, bristlecones grow at tree line or just below. They are unlikely looking champions. The largest of them do not reach 50 feet in height.
Trouet said the bristlecone has the right ingredients for longevity — slow growth, hard wood and an environment that is not attractive to insects.
Fast growth is not conducive to long life, she said, explaining why the list of big trees is not studded with denizens of tropical rain forests.
“As Neil Young would say: ‘They burn out rather than fade away,’” said Trouet.
The bristlecones easily last hundreds of years and sometimes thousands. Tree-ringers mine them to reconstruct past climate. They have combined cores of living trees — pencil-thin samples collected with boring tools — with information from dead trees, to create a climate chronology that spans 9,000 years.
The most famous bristlecone pine story concerns the late Donald R. Currey, who was a graduate student at the University of North Carolina when he cut down a bristlecone pine in 1964 on a peak in eastern Nevada to count its rings. The tree, called Prometheus, was found to be 4,862 years old. It was the oldest tree known to exist at the time.
Researchers from the UA Laboratory of Tree-Ring Research have discovered two older ones. The champion a 5,066-year-old tree, was core-sampled in 1957 by Schulman, who died in 1958. His sample sat, unexamined, in the archive at the UA tree-ring lab until researcher Tom Harlan, cross-dated the core just before his death in 2013.
Schulman, assistant to A.E. Douglass who established the science of dendrochronology, had turned his attention from giant sequoias, which grow at a fairly steady pace, to bristlecones. They were older and they grew in tough climates, producing a better record of wet and dry years in their rings.
That climate record is what Trouet and fellow researchers at the University of Arizona Laboratory of Tree-Ring Research were doing in Greece this year when they took a core sample of the Bosnian pine they named “Adonis.”
The group is comparing climate records left by old trees in Scotland and Greece to correlate with changing patterns in the jet stream over Europe.
They weren’t looking for the oldest tree, but it’s always nice to find one, Trouet said.
Adonis had been cored by Swedish dendrochronologist Paul Krusic in 2013, but his sampling tool was only 24 inches long.
In 2016, the team returned with a coring tool a full meter long.
Trouet said Krusic got some pushback in Europe, particularly in Sweden, when the discovery was announced. Some Swedes argue that the oldest tree in Europe is a 9,558-year-old Norway spruce that grows in Sweden.
That tree, said Trouet, is a clone. Its root system may be thousands of years old but its stem would not have more than 100 or so rings.
Tree-ringers aren’t all that interested in clones — or in trees whose interiors rot as they age.
That’s why Trouet also dismisses the claim of a 4,000-year-old yew tree on the grounds of St. Digain’s Church in Llangernyw village, Wales. The center is hollowed and you can’t simply extrapolate the age using the outer rings and a measurement of the tree’s radius.
Old trees grow slowly, she said. Younger rings are wider. It’s a “linear extrapolation” of a nonlinear phenomenon — the tree may be old, but you can’t prove it.
The same is true of olive trees which may be quite old, but elude measurement by tree rings.
Trouet also assumes that Asia has older trees than the 750-year-old Siberian larch.
There is, in fact, a historical record for a ficus or “bohdi” tree in Sri Lanka that is more than 2,000 years old, and there are “sugi” or Japanese cedars that are thought to be as old, though their interiors have also been hollowed by decay.
In Africa, a Namibian baobob tree called the “Grootboom” was considered the oldest tree on the continent until it died.
The new African oldie may be an Atlas cedar in the mountains of Morocco that was cored and cross-dated by Touchan of the UA tree-ring lab.
Touchan and a team have used the cedars of North Africa to reconstruct wet and dry years, finding that recent drought in the region is as bad as any in history.
Basically, the oldest trees are where the tree-ringers travel to document them.
“To be fair, a lot more tree-ring research has been done in the western United States than in Asia,” she said.
Dendrochronology is a science that began at the University of Arizona and concentrated, at first, in the western United States.
Douglass, the UA’s first astronomy professor, was already investigating tree rings in an attempt to correlate them with a long historical record of sun spots when he came to the UA in 1906.
He quickly zeroed in on the giant sequoias that were harvested for wood before John Muir and a nascent conservation movement lobbied for their protection. Douglass collected cuts and slabs from logged trees and shipped them back to Tucson. His discoveries are still No. 2 and No. 3 on the list of oldest sequoias .
The oldest sequoia identification was done by Touchan and his UA colleague Hughes.
Tree-ringers don’t purposely set out to break records, but there is a certain honor that goes with that, said Hughes.
Peter M. Brown, of Rocky Mountain Tree-Ring Research, keeps a list of the oldest documented trees, from which the record-holders in this story were identified. Brown doesn’t expect the bristlecone pine to be unseated as the overall champion, “but one never wants to say ‘never.’”
Some trees elude measurement, he said. They don’t reliably form rings or they hollow out as they age. “On mainland Australia, there are 300 recognized species of eucalypts and not a single one of them works for dendrochronological purposes.”
Brown hasn’t followed all the historical claims and does not consider a record official unless it has been verified by coring or some other means, such as radiocarbon dating.
Hughes said he is always skeptical of historical claims. He was once asked to core and date an apple tree that grew at Woolsthorpe Manor, the childhood home of Sir Isaac Newton in England. It was suspected of being the same tree whose falling apple inspired Newton’s gravitational theory.
“The apple tree is there and it’s in almost exactly the same position as one in an almost contemporaneous woodcut,” he said. But when Hughes investigated in 1978, he determined that the tree had begun its life in the early 20th century. Newton lived from 1643 to 1727.
He suspects a new tree of similar shape sprouted from the roots of the old one.