Pando, a unique “forest” in Utah’s Fishlake National Forest, often sparks the question: Is it the largest living organism on Earth? While appearing as a vast stand of trees, it functions as a single, interconnected entity. Comparing Pando to other colossal life forms highlights the complexities in defining what makes an organism “largest.”
What is Pando
Pando is a clonal colony of quaking aspen, Populus tremuloides, spanning approximately 43 hectares (106 acres) in south-central Utah. While it appears as a forest of individual trees, each of the estimated 47,000 “stems” is genetically identical and connected by an expansive, shared underground root system, making Pando a singular, massive organism.
The collective weight of Pando is estimated to be around 6,000 metric tons (6,600 short tons), or 13.2 million pounds. While individual stems typically live for about 100 to 130 years, the root system itself is considerably older. Latest estimates suggest the entire clonal organism could be between 16,000 and 80,000 years old, making it one of the oldest known living entities.
Defining Biological Immensity
Determining the “largest” organism is not straightforward, as size can be quantified in multiple ways. These include total mass or weight, geographical area, overall volume, or linear length.
Mass or weight refers to the total biomass an organism contains. Area or spread measures the geographical footprint an organism occupies, particularly relevant for organisms that grow horizontally or clonally.
Volume considers the total three-dimensional space an organism fills, often applied to individual structures like a tree trunk. Length measures the linear extent from one end of an organism to another, a useful metric for elongated creatures.
Pando’s Rank Among Earth’s Largest
When considering mass, Pando is widely regarded as the heaviest known single organism on Earth, estimated at 6,000 metric tons. For comparison, a blue whale weighs up to 200 metric tons, and the General Sherman Tree, a giant sequoia, weighs approximately 6,167 tons.
In terms of area, Pando’s 43 hectares (106 acres) also positions it as a significant contender. However, other organisms, particularly fungi, can cover even larger areas. The “Humongous Fungus,” Armillaria ostoyae, in Oregon’s Malheur National Forest, is reported to span up to 9.1 square kilometers (2,200 acres). More recently, a single clonal organism of seagrass, Posidonia australis, in Shark Bay, Australia, was found to cover an astonishing 200 square kilometers (77 square miles).
For total volume, Pando’s individual ramets are not as massive as giant sequoia trunks. The General Sherman Tree, for instance, holds the record for the largest single-stem tree by volume at 1,487 cubic meters. Pando’s immense size comes from its collective nature as a clonal colony, excelling in mass and spread rather than individual volume or linear length.
How Pando Achieves Its Scale
Pando’s immense size results from its unique clonal reproduction. Quaking aspens reproduce asexually through suckering, where new shoots (ramets) emerge from an extensive underground root system (rhizome).
Every “tree” within the Pando grove is genetically identical, sharing this single, vast root network. This interconnectedness allows the organism to distribute resources like water and nutrients efficiently across its entire expanse.
The root system also enables Pando to survive disturbances such as fires or logging, as new stems can regenerate from the protected underground network. This continuous regeneration, where older stems die and new ones sprout, contributes to Pando’s remarkable longevity and scale. The shared root system anchors the organism and facilitates nutrient gathering.