Pando, the massive ancient tree, is becoming three

Pando, the vast and ancient aspen tree in Utah in the US, is arguably the world’s largest living thing (other candidates include a fungus in Oregon and a seagrass off the coast of Western Australia).

But the hundred-acre colony of quaking aspen (P. tremuloides), all genetically identical and sharing a root system, is breaking up – and attempts to fix it may not be working.

Five years ago, researchers from Utah State University evaluated the state of Pando, finding it was under threat from deer and other herbivores.

Now, one of those researchers – Paul Rogers, an adjunct professor of ecology – has returned to see how things have changed, and evaluate the fencing which managers erected in some parts of the forest.

Rogers has published his findings in Conservation Science and Practice and says the management is sending Pando along three different ecological paths.

Two people standing in a forest with a line of tape, a transect line, suspended in a straight line through the forest
Field Technicians Rebekah Adams and Etta Crowley take vegetation measurement under Pando. Credit: Paul Rogers

In the 16% of the colony that has proper fencing, new aspen shoots can grow into trees before getting eaten.

A third of the stand has fencing, but it’s in poor repair. This means animals have been able to get in and older trees outnumber newer ones.

And in the remaining half of the stand, most young sprouts are getting eaten by deer and cattle.

This means mature aspens are dying without replacement, flooding the forest floor with sunlight, and changing the other plants in the stand.

Thus, argues Rogers, Pando is breaking into three parts, with markedly different ecologies.

Better fencing isn’t likely to be a perfect fix, either. The shoots in the properly fenced area are all the same age, which doesn’t reflect Pando’s natural growth.

Infographic labelled 'pando in pieces: a three-way split of the world's largest living thing', showing it divided into 50% with no fences and very sparse, 34% with damaged fences and some trees regrowing, and 16% fenced and recovering
The diverging ecologies of Pando. Credit: Lael Gilbert

“I think that if we try to save the organism with fences alone, we’ll find ourselves trying to create something like a zoo in the wild,” says Rogers.

“Although the fencing strategy is well-intentioned, we’ll ultimately need to address the underlying problems of too many browsing deer and cattle on this landscape.”

As well as fences, Rogers suggests “process-based restoration.”

“Examples of process-based restoration include, if not directly reintroducing predator–prey dynamics, then emulating those processes to the degree possible via more aggressive animal culling and greater movement of wild and domestic ungulates,” he writes in his paper.

He also argues for better monitoring, and policy changes to improve wider aspen conservation.

Please login to favourite this article.