All of the 47,000 aspens in the Pando forest come from a single root system, which makes it genetically one individual organism. (U.S. Department of Agriculture)

Meet Pando, thought to be the world’s largest living thing by mass. It’s a forest, but all of its 47,000 aspen trees come from a single root system spread over 106 acres in Utah, making it genetically one individual.

But Pando is dying. Hungry deer and cattle have been eating its young stems, and many of the oldest trees are reaching the end of their natural life span.

“It’s falling apart on our watch,” says Paul Rogers of Utah State University and the Western Aspen Alliance. “The old trees are dying, and the young ones are being eaten.”

At about 6,000 tons, Pando, which is Latin for “I spread,” is about 35 times heavier than the heaviest living animal, the blue whale. The largest living thing by area is thought to be a fungus in Oregon, while the record for the tallest thing is held by a redwood tree in California.

Pando is also likely to be the world’s oldest living organism, with estimates putting it at between 80,000 and 1 million years old. (The Department of Agriculture website on Pando says “an aspen clone starts with a single seed and spreads by sending up new shoots from the expanding root system. These shoots become trees that are genetically identical.”)

Saving it may be as simple as putting up a good fence.

To test that idea, Rogers and his colleagues fenced in 17 acres of the grove. They also tried to stimulate tree growth by burning vegetation, clearing juniper bushes growing among the trees and cutting mature aspens.

After three years, the part of Pando inside the fence contained more than eight times as many stems per hectare (equal to about 2.5 acres) as an unfenced area. Although the burning, clearing and cutting enhanced growth, simply excluding browsing animals caused most of the change, Rogers reported last week at the North American Congress for Conservation Biology in Madison, Wis.

“It was a neat surprise that we can get pretty good results with fencing alone,” Rogers says.

What works for Pando might not work elsewhere, however. Installing barriers around large regions of the American west or whole mountain ranges would be impractical, Rogers notes.

Sam St. Clair at Brigham Young University in Provo, Utah, agrees that the fence fix probably won’t work for aspens everywhere. “At a large scale, fencing isn’t going to work,” St. Clair says. “It’s too expensive.”

Still, for Pando at least, it looks like the proverb had it right: Good fences make good neighbors.

New Scientist