The United States is not only home to what is thought to be the oldest living single organism in the world—a fungi that grows in Oregon—it is also home to the oldest living tree.
The Methusalah tree, which grows in California’s White Mountains, is the oldest known living tree in the world. It is a bristlecone pine and has a verified age of 4,851 years. For some reference, the Pyramid of Djoser, which is the oldest pyramid in Egypt, is about 4,700 years old.
The bristlecone pine or Pinus Longaeva is a primary succession species, meaning it belongs to a group of plants that colonize bare sections of earth. The species is known to have a very long life span and often live to be 1,000 years old. The oldest known examples of these trees live at high altitudes where few other plants can survive and have an incredibly slow growth rate.
The lack of competition from other plants in the harsh mountain environment likely contributes to the long life of these trees. The short summer growing period in these areas is often just over 40 days. This means that sometimes the trees do not grow at all from year to year. The slow growth rate, due to the cold windy climate, produces trees that grow in twisted and gnarled forms much like that of ancient olive trees.
Though the Methusalah tree is alive, much of its trunk is dead with only a small portion of the tree and its roots still living. It can be determined which part of the tree is alive, as these parts are covered with bark, whereas the rest of the tree is bald. The living branches of the trees will also contain pine needles, some of which can remain on the branch for up to 40 years.
There are a few other examples of ancient bristlecone pines dotted around the western US, particularly Utah, Nevada and California. A bristlecone pine in Nevada was discovered to be the oldest living tree in existence only after it was cut down in 1964. The tree, named Prometheus, was estimated to be about 5,000 years old at the time it was felled.
It is not always possible to verify the age of ancient trees, as the heart wood has a tendency to decay in the center. This means that the usual way of determining their age, by counting the rings, has to be supplemented with a bit of informed guess work.
What the rings tell us
The study of tree rings is known as dendrochronology and is used not only to determine the age of trees, but to determine how the Earth’s climate has changed over the centuries. The varying tree samples, often collected by drilling out a thin section of wood, have been invaluable to scientists providing a catalog of data stemming back thousands of years.
In relatively recent history, there have been two significant periods of climate change, known as the Little Ice Age and the Medieval Warming Period. In these eras, the climates of Europe and North America were seriously disrupted for hundreds of years.
The existence of these ancient trees in North America, which are incredibly rare in Europe, has provided scientists with data that would otherwise not be available.
Most of us know of the giant redwoods and how the Coast Redwood or Sequoia sempervirens are the tallest trees on Earth. Though the average age of a redwood tree is about 500-700 years, some have been known to exceed 2,000 years. The largest population of redwoods can be found in California and Oregon. The trees have a long history there dating back at least 20 million years.
The history of redwoods goes back considerably further still and it’s believed they first grew on Earth about 240 million years ago. This is around the same time as dinosaurs also made an appearance. Comparatively, modern humans have existed for only about 200,000 years.
These gigantic trees have some clever ways of maintaining themselves over long life times.
Though many trees can be killed by forest fires, redwoods are quite impervious to it. They sequester large amounts of water inside their trunks and have incredibly thick bark.
They also contain tannin, which does not burn and contain low levels of resin that makes other tree varieties so flammable. The fact that they are so impervious to fire meant that redwood timber was a valued commodity in the last centuries. It’s thought that up to 95% of California’s redwood forests were cut down from the mid-1800s for use as timber.
Another of North America’s ancient trees is actually not a single tree but a colony of quaking aspen (Populus tremuloides) in Fishlake National Forest, Utah. The colony, known as Pando which is Latin for “I spread,” is thought to be anywhere upto 14,000 years old.
A clonal colony is formed when a plant reproduces vegetatively rather than sexually. This means that it sends up a new shoot from its root system rather than by producing seeds that are fertilized and scattered. Therefore, the trees in the colony are all genetically identical and this is why they are called clones.
The Pando colony covers about 108 acres and consists of over 40,000 stems. The maximum age for a quaking aspen is about 130 years and when one tree dies, a new stem shoots up in its place. This means that though the oldest trees are only just over a hundred years old, their root system and genetics are much older.
There is a real wealth of natural treasures in North America, not to mention ancient natural artefacts that, in many cases, exist only here. The fact that the country remained relatively free of agriculture and human interference until the last few centuries means this deep history has been preserved for us all to marvel at. Let’s hope we can do the same for future generations.