Pando, World’s Largest Single Organism, is Shrinking

A team of researchers from Utah State University has conducted the first complete assessment of the Pando aspen clone — the largest living organism on Earth — and the results show continuing deterioration of this unique ‘forest of one tree.’

The Pando aspen clone from a distance (green foreground and middle -- not yellow). Image credit: Lance Oditt, Studio 47.60° North.

The Pando aspen clone from a distance (green foreground and middle — not yellow). Image credit: Lance Oditt, Studio 47.60° North.

The Pando aspen clone, also known as the Trembling Giant, is the largest known organism on our planet in terms of dry-weight mass.

This ‘forest of one tree’ has an estimated mass of 5.9 million kg, covers some 106 acres (43 ha) in south-central Utah’s Fishlake National Forest.

It consists of more than 47,000 genetically identical above-ground stems or ‘ramets’ originating from a single underground parent clone.

The clonal colony was first described in the 1970s and was later named ‘Pando’ (Latin: I spread) based on its vegetative reproductive strategy and alleged ancient lineage.

It is threatened in particular by herbivory, and current management activities aim to reverse the potential for type conversion, likely to a non-forest state.

According to the new study, early protection from fencing showed great promise in abating browser impacts, which have nearly eliminated recruitment of young aspen stems for decades now. However, follow-up fencing of a larger area is currently failing.

“After significant investment in protecting the iconic Pando clone, we were disappointed in this result,” said Dr. Paul Rogers, lead author of the study.

“In particular, mule deer (Odocoileus hemionus) appear to be finding ways to enter through weak points in the fence or by jumping over the eight-foot barrier.”

“While Pando has likely existed for thousands of years — we have no method of firmly fixing its age — it is now collapsing on our watch.”

“One clear lesson emerges here: we cannot independently manage wildlife and forests.”

The study is published in the journal PLoS ONE.

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P.C. Rogers D.J. McAvoy. 2018. Mule deer impede Pando’s recovery: Implications for aspen resilience from a single-genotype forest. PLoS ONE 13 (10): e0203619; doi: 10.1371/journal.pone.0203619

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