The forest that's really a single tree

In Fishlake National Forest, in Utah, grows Pando: some 47,000 quaking aspen trunks that look like separate trees. They aren't. Underground they share a single root system and the same DNA, so technically they form one organism.

It's one of the heaviest living things known: it weighs around 6,000 tonnes and covers more than 40 hectares. Every spring all its stems leaf out at once, like a single body spread across the hillside.

Its age is a wonderful mystery: estimates run into thousands of years, and some go as far as tens of thousands. It would have been sprouting long before writing existed.

Next time you walk through a forest, think about it: maybe you're not among many trees, but inside one huge one that has stood there since the last Ice Age.