Pando, tree clone of the Wasatch plateau, Utah Inga Spence/Visuals Unlimited/Getty

Meet Pando, thought to be the world’s largest living thing by mass. It’s a forest, but all of its 47,000 trees come from a single root system spread over 43 hectares 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 lifespan.

“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 6000 tonnes, Pando, which is Latin for “I spread”, is some 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 tallest record is held by a redwood tree in California.

Pando is also likely to be the world’s most ancient living organism, though estimates of its age vary widely, from 2000 years to 1 million years old.

But saving it may be as simple as putting up a good fence.

To test their idea, Rogers and his colleagues fenced in 7 hectares of the grove. They also tried to stimulate tree growth by burning vegetation, clearing juniper bushes growing among the trees, and cutting mature aspens, all of which can cause new trees to sprout.

After three years, the part of Pando that was inside the fence contained more than eight times as many stems per hectare as an unfenced area. Though the burning, clearing and cutting enhanced growth, simply excluding browsing animals drove most of the change, Rogers reported last week at the North American Congress for Conservation Biology in Madison, Wisconsin.

“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 neighbours.