On the Fishlake National Forest along the southwest corner of Fish Lake in central Utah, USA. The access highway (state route 25) runs through the middle of the clone between 6.0 - 6.6 miles (9.6 - 10.6 km) from the Highway 24 turnoff.
Approximately 106 acres (43 ha) and weighing an estimated 13 million lbs (5.8 million kg).
We don't have a good answer with current science. We do know that the oldest individual stems are between 120-150 years old, but we cannot accurately date the age of the clone at this time.
We don't know if the entire clone is dying, but there have certainly been a lot of individual stems dying and falling down in the past decade. Of more concern to managers and scientists is, why are there so few young Pando stems to replace the dying ones? Again, we don't know for sure, but we are aware that browsing by large herbivores (elk, deer, cattle) is probably the main problem.
The US Forest Service is erecting and maintaining fences around much of the clone to prevent young aspen stems from being browsed. We hope to remove the fences when these sprouts (also called suckers) reach the height (6 ft./2 m) where they can no longer be eaten. Utah State University is also conducting experiments to test different treatment methods - fire, cutting, removing competing vegetation - that may help to stimulate additional suckers.
We believe it is a natural process for most mature stems to die between 80-150 years of age. However, what is probably "unnatural" is the amount of browsing of the young aspen stems arising from the roots. These new sprouts/suckers are Pando's lifeline to the future. This clone has probably lived for a very long time, but something that has happened in the past few decades is causing an interruption in regeneration. The most likely explanation is that human management of the forest and/or browsers has fundamentally changed. Thus, we are probably to blame and should play a significant role in fixing the problem.
This large (and probably old) clone is under some of the same threats as much larger landscapes that are dominated by aspen in all of the western states. If we can use Pando as a "proving ground" for restoration, it is hoped that the methods may supplement solutions to larger aspen die-offs around the region.