Hidden along a Utah highway, a single organism masquerades as a forest of aspen trees. This colony, known as Pando (Latin for “I spread”), occupies 106 acres of Fishlake National Forest and weighs an estimated 13 million pounds—over 5,000 times the mass of a bison, the largest land mammal in the United States.
Researchers who first catalogued this remarkable clonal system in the 1970s used a clever combination of genetic sampling and growth analysis to determine its age. A recent pre‑print posted on bioRxiv in October 2024 analyzed more than 500 DNA samples and estimated Pando’s age at 34,000 years, with a plausible range of 16,000 to 80,000 years. While the study awaits peer review, its findings would make Pando the oldest‑known living organism and the largest by mass.
Pando is a quaking aspen (Populus tremuloides), the most widespread tree species in North America. Though capable of sexual reproduction, aspens predominantly clone themselves: new stems emerge from a shared root system, grow through the soil, and develop into trunks that appear as individual trees. Each stem bears flowers and sheds leaves in unison, a tell‑tale sign of a clonal colony.
The original root mat that founded Pando sprouted during the last glacial period, but the initial stem has long since perished. Individual stems live between 50 and 150 years before being replaced by new growth. Today, Pando comprises roughly 47,000 stems; the oldest surviving ones are about 130 years old. Theoretically, the clone could grow indefinitely, yet its demographic profile now resembles a population of senior citizens with few young or middle‑aged recruits.
Aerial imagery spanning the past seven decades reveals a steady decline in Pando’s density. Stems die off faster than new sprouts can replace them, largely due to grazing pressure. Mule deer, whose populations expanded after the removal of predators in the early 1900s, consume new shoots before they mature. Cattle also pose a significant threat; seasonal grazing by livestock on Fishlake National Park’s lands destroys undergrowth that supports the colony.
In response, the U.S. Forest Service has installed protective fencing around portions of the colony, and those fenced areas have shown signs of recovery. However, only about half of Pando remains protected, leaving the unprotected segments vulnerable. Pando’s resilience over tens of thousands of years suggests hope, but continued conservation efforts are essential to secure its future.
For more detailed information, visit the U.S. Forest Service and the National Park Service.
