At first glance, it looks like an ordinary grove of quaking aspens.
Tens of thousands of white trunks rise into the sky, their coin-shaped leaves shimmering in the breeze before turning a brilliant gold each autumn. But appearances can be deceiving.
Hidden within Utah's Fishlake National Forest is Pando, a grove that is not a forest at all but a single living organism. Every one of its estimated 47,000 trunks is genetically identical, all connected by one vast underground root system.
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Pando grows high on Utah's Colorado Plateau where cool mountain conditions have allowed aspens to flourish for thousands of years. Although visitors can walk among its trunks, few realise they are standing inside a single giant tree.
Covering around 43 hectares (106 acres) and weighing an estimated 6,000 tonnes - roughly the equivalent of 43 blue whales - Pando is widely regarded as the world's largest known tree by mass. Scientists believe it may also be one of Earth's oldest living organisms, with some estimates suggesting it could be close to 9,000 years old meaning it has survived dramatic climatic shifts since the end of the last Ice Age.But exactly how old Pando is remains uncertain.
Its name comes from the Latin Pando, meaning "I spread"- a fitting description for a tree that has quietly expanded beneath the soil for millennia.
Unlike most trees, which reproduce through seeds, Pando continually renews itself by sending up new shoots directly from its roots. What appear to be individual trees are simply stems emerging from one enormous living network.
"It reproduces not by seed like a lot of trees, but by asexual reproduction," explains Professor Paul Rogers, Director of the Western Aspen Alliance at Utah State University.
"It just sprouts directly from the roots, regenerating genetically identical stems. Whenever the organism is under stress, its response is to produce thousands and thousands of offspring in the hope that some will survive."
"I think what makes it unique is the size and potentially the age," he says. "This very large organism has been around for so long and survived on this Earth. To put it in a contemporary context, it is kind of falling apart in our time. That makes us stop and think about our relationship with it and perhaps our relationship with the Earth in general."
Pando is also far more than a giant tree - it forms the foundation of an entire ecosystem. Aspen is considered a keystone species, supporting an exceptional diversity of life.
Birds such as downy woodpeckers depend on the varying ages and heights of the trees, while a rich carpet of wildflowers and shrubs beneath the canopy provides food and shelter for insects, mammals and countless other species.
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"The aspen is known as a keystone species, supporting a lot of other plants and animals," explains Professor Rogers. "Different stages of the trees create structural diversity, and that supports a large array of wildlife living there every day."
Given its ancient resilience, it might seem surprising that Pando is now under threat. Climate change is often blamed but the picture is more complex. Scientists believe increasingly severe droughts could reduce the tree's ability to regenerate by depleting the underground energy reserves needed to produce new shoots. Yet Professor Rogers says the most immediate danger comes from something much closer to home.
"The biggest threat is that all the young ones are being eaten," he explains.
For decades, mule deer and cattle have browsed heavily on young aspen shoots before they have a chance to mature. Without new stems replacing older ones, the giant organism gradually ages.
"It would be like living in a town of 50,000 people where 45,000 were over the age of 80," he says. "That's our basic problem."
At the same time, predators including wolves and grizzly bears, which once helped keep deer numbers and movements in balance, have disappeared from the area.
"When we throw that balance out of nature, we have some problems,” he added.
Researchers continue to monitor Pando closely, hoping that careful management can encourage young stems to survive and ensure this remarkable organism continues to regenerate.
For Professor Rogers Pando represents something bigger than conservation science.
He hopes inspiring wonder may be the first step towards protecting places like Pando.
"It's good for us to be inspired," he says. "Imagine placing yourself inside something so immense - literally standing within an organism that's the size of about 43 blue whales. To be inspired by our planet is to start to respect it, and to respect it is to start taking action to preserve these things, which are ultimately good for ourselves as well as the planet."
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