A Forest of One
In Utah's Fishlake National Forest, what appears to be a grove of individual quaking aspens is a single genetic entity. Named Pando, from the Latin for "I spread," this organism is a clonal colony of a single male quaking aspen (Populus tremuloides). All 47,000 stems are genetically identical clones, connected by a vast, shared underground root system. This single organism covers 106 acres (43 hectares) and has an estimated weight of 6,000 metric tons (13.2 million pounds), making it the most massive known organism on Earth by weight.
The age of Pando's root system is difficult to calculate precisely because it constantly regenerates. Estimates of its origin range from the end of the last ice age, around 14,000 years ago, to as much as 80,000 years. While the root network is ancient, the individual stems, or ramets, have an average lifespan of about 130 years before they are replaced by new shoots from the roots. This continuous cycle of death and regrowth has allowed the organism to persist for millennia. The fluttering of the leaves in even a light breeze, a trait of the species, gives the organism its nickname: The Trembling Giant.
A Giant in Decline
Pando is showing signs of decline because it is failing to regenerate. For the organism to survive, new shoots must grow from the root system to replace the older, dying stems. For decades, this recruitment of young stems has nearly stopped. The primary cause is overgrazing by mule deer and elk. These animals consume the tender new shoots before they have a chance to mature into full-grown stems.
Human activity has contributed to this problem. The removal of natural predators like wolves and cougars has allowed herbivore populations to increase. The suppression of natural wildfires, which would historically clear out competing conifers and stimulate new aspen growth, has altered the local ecosystem. Pando is also affected by diseases like sooty bark canker, leaf spot, and conk fungus. To combat the decline, conservation efforts focus on fencing off sections of the colony to prevent grazing. These protected areas show promising regrowth, but much of the organism remains vulnerable.