Christopher Booker:

Whether you're sitting under its canopy, or looking at it from above, its difficult to comprehend that all of these leaves, the branches and the trunks that support them, are one single organism. What looks like a forest is actually one single tree. Located in Utah's Fishlake National Forest- the tree spans 106 acres- the equivalent of 80 football fields. But what's up top, covers what's happening below: an intricate root system that supports the most massive living thing known to exist on earth. It's called Pando.

The nickname is Latin for "I spread" but the tree is what's known as a Quaking Aspen clone. That means each leaf, branch and trunk are genetically identical. Some leaves may be larger, some trunks taller, but if you look at the DNA, there is no difference. Aspen clones of various sizes can be found all over the Northern Hemisphere.

There is debate about just how old this tree is – some scientists estimate that it has existed for thousands of years, but its' remarkable longevity is at risk. Pando is starting to die. Professor Paul Rogers is the director of Utah State University's Western Aspen Alliance. He compares Pando to a human community.