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Sometime just after the last Ice Age, a single aspen seed sprouted in western North America. For millennia, this solo seed spread through the forest, sending new shoots and expanding its root system through what is now known as the state of Utah. Each of these clones continued to grow, making up one vast organism. Today, “Pando” is made up of more than 47,000 genetically identical aspen trees weighing 5.9 million kilograms (13 million pounds), spanning across 43 hectares (106 acres).
It’s also in danger of dying out and it’s mostly our fault.
“Aspen forests (chiefly Populus tremuloides, P. tremula) are among the most widespread tree systems in the world, yet their sustainability is threatened by human-induced impacts such as warming climates, development, fire suppression, and unchecked herbivory,” notes a new study published in PLOS ONE.
A combination of fire suppression and prolonged drought has taken its toll on the aspen grove, but the researchers note the biggest threat comes from mule deer and other ungulates who dine on the aspen offshoots.
Researchers monitored 65 plots in three randomized management areas by measuring the alive and dead mature trees, stem recruitment and regeneration, overall forest and shrub cover, and presence of deer feces. They then compared these current forest conditions to 70 years of sequenced historical photos.
“This first comprehensive assessment of conditions at the famed Pando aspen clone reveals an ancient forest threatened by recent human decisions,” they wrote.
For years, deer and other ungulate populations have been left unchecked. Throughout much of the last two centuries, western pioneers hunted apex carnivores that feed on deer to such low numbers that ungulate populations have skyrocketed. Furthermore, management policies aim to encourage high game populations for hunting. With the exception of fencing, there are hardly any barriers keeping ungulates from dining on aspen shoots. The solution, the researchers say, may rest in management’s ability to shift their policy to take on a more holistic perspective.
“A vital lesson derived from this study is that independently managing vegetation and wildlife may harm both,” wrote the authors. “While several human alterations to this forest have taken place in recent decades, it is the lack of simultaneous herbivore regulation that has caused this stand’s degeneration.”
Map depicting the study area within the Pando aspen clone, Utah, USA. PLOS ONE
