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A Giant Quaking Aspen Forest Is Trembling Under Our Watch

A cloned aspen grove that's thrived for millennia is feeling the pressure of just 50 years of human activity.
The Pando clone stands above Scenic Byway Utah-25 in Fishlake National Forest, Utah.

The Pando clone stands above Scenic Byway Utah-25 in Fishlake National Forest, Utah.

The heaviest known living organism in the world, according to multiple assessments, resides in Utah. It stretches across the Fishlake National Forest, soaking up the sun and outliving its competitors atop the Colorado Plateau. It weighs, conservatively, 13 million pounds. Its name is Pando, Latin for "I spread"—fitting, because it's a giant forest of genetically identical quaking aspen stretched across 106 acres with an estimated 47,000 trees. And, according to a new study in the journal PLoS One, it's in danger.

The study's lead author, Paul Rogers, is the director of the Western Aspen Alliance, a collaboration between Utah State University, the Bureau of Land Management, and the Forest Service. The alliance's focus and research interest is Populus tremuloides, the quaking aspen: Pando's species. And Rogers is a noted expert on Pando. His conclusions aren't new, either: He's been telling news outlets for years that Pando is dying under our watch, and something has to be done.

This aspen stand, also known as The Trembling Giant, came of age in near-perfect conditions—its exact age is hard to date, but evidence suggests it's been cloning itself and spreading across the plateau for millennia. It probably thrived on rejuvenating fires that wiped out its competition, allowing it to send its roots out for miles, producing new aspen suckers everywhere it went. But after just half a century of human impact, it's struggling.

The researchers compiled aerial photos of the forest from 1939 to 2011 and created comprehensive geographic information system maps of the clone. That work shows an overall reduction in aspen coverage. The important question was why. One fenced-off section of the forest was thriving, revealing an answer: hungry deer. The immediate culprits are grazing herbivores—especially mule deer—who are eating the tree's young suckers before they have the chance to grow and replace older trees in the forest. If Pando can't successfully regenerate, the forest thins out.

But in a larger sense, humans are to blame. Although there have been multiple interventions on behalf of the aspen stand, forest and wildlife management practices often occur separately—and there's been no simultaneous regulation of herbivory and grazing. Crucially, there are more herbivores eating the baby aspen thanks to humans: Mule deer and other ungulates are thriving as a result of policies encouraged by hunters, who want plenty of game to pursue. Plus, there are cabins and campsites near Pando, and human recreation doesn't mix well with apex predators like wolves and bears, who have been chased or killed off.

The Pando forest is an especially useful point of research because its trees are identical, eliminating many potential confounding variables. And it holds clues that can help us understand other aspen forests and how to help them. Rogers' study discusses how conservation efforts often focus on a single endangered species, not ones present in large numbers across the world like aspen. The authors suggest that promoting the health of ecosystems on a continental basis might be a more effective way to help species.

For Pando, the answer could be as simple as effective fencing to keep the herbivores out. It's not cheap (mule deer are great at getting through gaps or jumping the fence, so it requires close surveillance) and it's not popular (currently, most of the grove is open to humans), but it might just save the giant and all the life that depends on it. Even though, genetically, Pando is one tree, it and the other quaking aspen forests across the continent are key to maintaining high levels of biodiversity.