Pando is thought to have grown for much of its lifetime under ideal circumstances: frequent fires have prevented its main competitor, conifers, from colonizing the area, and climate change, transitioning from a wet and humid weather pattern to semi-arid, has obstructed widespread seedling establishment and the accompanying rivalry from younger aspens.
During intense fires, the organism survived by its root system, sending up new stems in the aftermath of each wildfire. If its postulated age is correct, the climate into which Pando was born is markedly different from that of today, and it may be as many as ten millennia since Pando's last successful flowering, according to an OECD report: However, others have observed that both flowering, and successful large-scale seedling establishment, occur frequently, even during dry years, in the modern period, invalidating the dating method.
Pando was discovered by Burton V. Barnes of the University of Michigan in the 1970s. Barnes was widely considered an expert on North American aspen at the time, having been one of the first to describe the clonal growth of aspen from an extensive root system as part of his dissertation at Michigan in the late 1950s. Barnes had described Pando as a single organism based on its morphological characteristics. Michael Grant of the University of Colorado at Boulder re-examined Pando and claimed it to be the world's most massive organism in 1992.
In 2006 the United States Postal Service made a stamp in commemoration of the aspen, calling it one of the forty "Wonders of America. In 2005 Lewis Libby wrote a letter to Judith Miller of the New York Times, who was jailed for refusing to reveal her sources in the White House, which used the Pando an allegory for teamwork.
Out West, where you vacation, the aspens will already be turning. They turn in clusters, because their roots connect them.
The clonal colony encompasses 43 hectares (107 acres) and has around 47,000 stems, which continually die and are renewed by its roots. Many of the stems are connected by its root system. The average age of Pando's trunks (or technically, stems) is 130 years, as deciphered by tree rings. Michael Grant in BioScience said:
Some experts speculate that Pando's reign since 1992 as the heaviest-known organism may be short lived. Less well-studied Quaking Aspens in Utah may be 80 hectares in extent and one million years old. Other large colonies could exist elsewhere. A clonal colony of at least seven Coastal Redwoods could weigh more, although no such stand is known to exist. Other scientists think that portions of Pando's root system may be dead and might have led the plant to split into separate groups and therefore would not be one organism, though the collective groups would remain the same singular, genetic individual.
Tree experts also note that the organism's age cannot be determined with the level of precision found in tree rings; some claim Pando's age is closer to 1 million years. Its current 80,000 year designation is based on a complex set of factors including the history of its local environment such as: The evidence indicating that there are few if any naturally occurring new aspens in most of the western United States since a climate shift took place 10,000 years ago and eliminated favorable soil conditions for seedlings; the rate of growth (including the differences of rates in distinct climates when accounting for its local-climate history, that males grow slower than females, and that aspens grow slower at higher elevations – Pando is at 2697 m, or 8,848 ft, above sea level); its size; and its genetic code in comparison to the mutations found among aspens born in the modern era. Michael Grant summed it thus:
This is however not supported by other observations in the region, which show that seedling establishment of new clones is regular, and often abundant on sites exposed by wildfire. J. L. Howard (U.S. Forest Service Fire Effects Information System) states: