It’s old, it’s massive, and it’s wobbly. The huge aspen stand called “Pando,” located in south-central Utah, has more than 100 acres of genetically identical aspen plant life, believed to be the largest living organism on earth (based on dry weight mass, 13 million pounds). What looks like a bright panorama of individual trees is actually a group of genetically identical stems with an immense shared root system.
Now, after a life that could have spanned millennia, the “trembling giant” is starting to break down, according to new research.
Paul Rogers, assistant professor of ecology at Quinney College of Natural Resources and director of the Western Aspen Alliance, completed the first comprehensive assessment of Pando five years ago. He showed that browsing deer (and, to a lesser extent, cattle) harmed the stand, limiting the growth of new suckers and putting an effective expiration date on the colossal plant. As older trees aged, new aspen shoots did not survive the voracious browsers to replace them. Pando was slowly dying.
In response to the threat, stewards erected fences around a section of the stand to keep the grazing animals out, creating an experiment of sorts. Rogers recently returned to evaluate the strategy and to do a good check on Pando’s overall health. He reported his findings in the journal Conservation Science and Practice.
According to the research, Pando appears to be taking three different ecological paths depending on how the segments are managed. About 16 percent of the stand is adequately fenced to prevent animals from passing through; new aspen suckers that survived the tender first years to establish themselves on new trees. But in more than a third of the stand, the fencing had deteriorated and was only recently reinforced. The previous navigation still has adverse impacts in this section; old and dying trees still outnumber young ones.
And the areas that remain unfenced (about 50 percent of the stand) continue to have concentrated levels of deer and cattle that consume most of the young shoots. Those affected areas are now changing ecologically in different ways, Rogers said. Mature aspen stems die without being replaced, opening up the canopy and allowing more sunlight to constantly reach the forest floor, which alters the composition of the plant. These unfenced areas are experiencing the fastest aspen decline, while the other fenced areas are taking their own unique courses, in effect breaking up this unique and historically uniform forest.
The solution to Pando’s survival, Rogers said, might not just be more fencing. Although unfenced areas are rapidly disappearing, fencing alone encourages single-age regeneration in a forest that has maintained itself over the centuries through variable growth. While this may not seem critical, patterns of aspen and understory growth at odds with the past are already occurring, Rogers said.
In Utah and the West, Pando is iconic and something of a canary in the coal mine. As a keystone species, aspen woodlands support high levels of biodiversity, from grouse to thimbleberry. As aspen ecosystems flourish or decline, countless dependent species follow suit. Long-term failure of new recruitment in aspen systems can have cascading effects on hundreds of species that depend on them.
Also, there are aesthetic and philosophical problems with a fencing strategy, Rogers said.
“I think if we try to save the organism with just fencing, we’ll find ourselves trying to create something like a zoo in the wild,” Rogers said. “While the fencing strategy is well-intentioned, ultimately we will need to address the underlying issues of too many deer and cattle in this landscape.”
Pando is a paradox. It has a reputation for being the largest organism on earth, but it’s relatively small in the big picture of conservation challenges around the world, or even just in Utah, he said. But as a symbol, it speaks to the fate of amol diversity and healthy human interactions with the earth in general. Lessons learned while protecting Pando also provide insight into the struggling aspen forests that span the Earth’s northern hemisphere.
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