A clonal colony of quaking aspen in Utah, covering 43 hectares and weighing 6 million kilograms — a single organism spread across an entire hillside, potentially the oldest and heaviest living thing on Earth.
Pando looks like a forest. It has 47,000 trees, each one a quaking aspen with grey-white bark and leaves that tremble in any breeze, the same trembling that gives the species its name. The trees range in height from ten to thirty metres. The canopy covers 43 hectares of hillside above Fish Lake in Utah.
It is not a forest. It is one tree.
All 47,000 trunks are genetically identical. They share a single root system — a vast, interconnected network of roots running through the soil beneath the entire site — and every trunk is a sprout from that system, not a separate organism that has seeded and grown but a sucker pushed up from the communal root. When fire passes through, or insect infestations kill the canopy, the root system survives and regenerates new trunks. The roots are very old.
Estimates of Pando''s age range from 8,000 to 80,000 years. The conservative estimate is based on stable climate periods in Utah''s geological past. The upper bound assumes the root system has been continuously regenerating since before the last ice age. Under that estimate, Pando was alive during the Upper Paleolithic — when anatomically modern humans were painting caves in France and Spain, this root system was already covering a hillside in Utah.
The organism weighs approximately 6 million kilograms. It is believed to be the heaviest living organism on Earth, and possibly the oldest. Current research suggests it may be dying — the canopy is not regenerating as fast as old trunks are lost.