But Pando is dying and may have only a few more years of glory.
It's a grove of quaking aspen trees spanning 106 acres near Fish Lake. Scientists call it an aspen clone, which is essentially a single plant comprised of thousands of trees connected by underground roots. When Pando was discovered a few decades ago, scientists named it with a Latin word that means "I spread."
An aspen clone starts with a single seed and spreads by sending out underground sprouts that emerge to become trees. In the 1970s, scientists tentatively mapped Pando's boundaries. More recently, Utah State University geneticist Karen Mock wondered if Pando's reputation as the world's largest known organism was overblown.
"So we set out to either confirm or deny that," she said.
Mock took DNA samples from 209 trees, mostly within that boundary. Her testing verified what was long suspected. "Genetically, in fact, Pando is one enormous clone over 100 acres," Mock said, "probably over 40,000 individual trees."
In all, Pando weighs about 13 million pounds, which makes it by far the most massive organism ever found.
"There may well be some larger clones than Pando out there," Mock said. "But it's the largest organism that's been described" by scientists.
As Pando's fame spread, the U.S. Postal Service honored the Utah curiosity as one of "40 Wonders of America." A postage stamp issued in 2006 may have set some sort of a record for making something very small out of something very big.
But now, Pando is in serious trouble, according to ecologist Paul Rogers of Utah State University.
"I would call it a crisis, yes," Rogers said.
When he visited Pando two years ago, the clone seemed reasonably healthy. But when he went back with a team of forestry experts three weeks ago, he was shocked. "We're looking at a situation," Rogers said, "where the whole clone could crash pretty quickly here, within the next few years."
The bark of Pando's mature trees shows they're dying from drought and beetles. That's typical of aspen stands throughout the West and, by itself, is not especially worrisome. What is more disturbing is that small trees and sprouts have vanished from the area spanned by Pando.
"There was no regeneration and there was no mid-story tree," Rogers said. "So if you might think of those as the young ones and the juveniles, there's no young ones to replace those dying trees. So this set off alarm bells."
Rogers said there is an overabundance of deer and elk in the area, and he believes the wildlife is feeding on the young sprouts. He also said a small amount of livestock grazing in the area is playing a minor role.
Rogers wants to fence out the deer and elk. A small portion of Pando, less than 10 percent, is already fenced and is thriving and regenerating.
Some government agencies are looking into the emergency fencing proposal, but that strategy is sure to be controversial. Fences would have to be quite high to be effective in holding out deer. At least one rancher also has grazing rights in the area. Another complication is that recreationists may have concerns about a high fence in such a scenic area. A U.S. Forest Service campground adjacent to Fish Lake is actually within Pando's biological boundaries.
If Pando does die out, or becomes sharply reduced in size, it would be particularly poignant because of the clone's presumed age. Pando is conceivably the oldest living thing ever studied. A recent study pegging Pando's age at 80,000 years led to media coverage in Europe. But other scientists are skeptical because there's no reliable way to determine the age of an aspen clone.
"People's estimates go from, you know, perhaps, low-thousands, up to even a million years old," Mock said. "Nobody really knows, and we don't have a very good way of asking that at this point, unfortunately."
Rogers believes that if nothing is done, Pando may shrink to become an ordinary, unspectacular remnant of its former glory.
"So we really need to hold on to this international treasure," Rogers said. "But it's slipping away very quickly."
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