Pando Is The Largest Living Organism on Our Planet – And It Is Breaking Up

Pando is the largest living organism on our planet – and it’s falling apart – Astrobiology

It’s old, it’s massive and it’s shaky. The gargantuan stand of aspen trees nicknamed “Pando,” located in south-central Utah, comprises more than 100 acres of trembling, genetically identical plants, considered the largest living organism on earth (based on dry mass, 13 million pounds).

What looks like a glittering panorama of individual trees is actually a group of genetically identical stems with a huge shared root system.

Now, after a life that may have spanned millennia, the “trembling giant” is beginning to crumble, new research suggests.

Paul Rogers, assistant professor of ecology at Quinney College of Natural Resources and director of the Western Aspen Alliance, conducted Pando’s first comprehensive assessment five years ago. He showed that deer browsing (and to a lesser extent cattle) harmed the stand, limiting the growth of new aspen suckers and setting an effective expiration date for the colossal plant. As old trees aged, new aspen shoots did not survive voracious browsers to replace them. Pando was slowly dying.

In response to the threat, managers erected a fence around a section of the stand to keep grazing animals out, creating a sort of experiment. Rogers recently returned to assess the strategy and to properly check on Pando’s overall health. He reported his findings in the journal Conservation Science and Practice.

Infographic illustrating the divergent ecologies of the world’s largest living organism, a stand of aspens called Pando. CREDIT Infographic by Lael Gilbert

Pando appears to take three disparate ecological pathways based on segment management, the research found. About 16 percent of the stand is adequately fenced to prevent browsing animals; new aspen suckers surviving those early tender years to establish themselves in new trees. But on more than a third of the stand, the fences had fallen into disrepair and were only recently reinforced. Past navigation still has negative impacts in this section; old and dying trees always outnumber young ones.

And areas that remain unfenced (about 50 percent of the stand) continue to have concentrated levels of deer and cattle consuming most of the young growth. These hard-hit areas are now changing ecologically in distinct ways, Rogers said. Mature aspen stems die back without being replaced, opening up the upper story and allowing more sunlight to consistently reach the forest floor, changing plant composition. These unfenced areas are experiencing the fastest decline of aspens, while the other fenced areas follow their own unique course, effectively breaking up this unique and historically uniform forest.

The solution to Pando’s survival, Rogers said, might not just be more fencing. While unfenced areas die off quickly, fencing alone encourages single-age regeneration in a forest that has sustained itself over centuries through variable growth. While it might not sound critical, aspen and understory growth patterns at odds with the past are already happening, Rogers said.

In Utah and throughout the West, Pando is iconic and looks like a canary in the coal mine. As a keystone species, aspen forests support high levels of biodiversity, from chickadees to blueberries. As aspen ecosystems thrive or decline, myriad dependent species follow suit. The long-term failure of new recruitment in aspen systems can have cascading effects on hundreds of species that depend on them.

Plus, there are aesthetic and philosophical issues with a fencing strategy, Rogers said.

“I think if we try to save the organism just with fences, we’ll end up trying to create something like a zoo in nature,” Rogers said. “While the fence strategy is well intentioned, ultimately we will need to address the underlying issues of too many deer and cattle grazing in this landscape.”

Pando is a paradox. It’s reputedly 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 aspen diversity and healthy human interactions with the earth as a whole. Lessons learned while protecting Pando also offer perspective on the struggling aspen forests that span Earth’s northern hemisphere.

Pando’s Pulse: Vital Signs Signal Need for Course Correction in World-Famous Aspen Forest, Conservation Science and Practice


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