Meet Pando, one of the oldest organisms on Earth. National Forest in central Utah, located about 200 miles south of Salt Lake City, is home to one of the most unique organisms on Earth. This individual is not some exotic animal or even a particularly rare species. Instead, it is a 106-acre grove of aspen trees (Populus tremuloides). This forest is special because it is made up of a single genetic individual. Each tree and branch in this forest is an exact clone of every other.
The clone’s name, “Pando” and it means “I spread” in Latin. This describes the reproductive strategy of all aspens. They send up new shoots from their roots as they spread throughout the forest. Meet Pando, one of the oldest organisms on Earth
All of the trees in an aspen grove are connected through this underground network of roots. In this way, aspens continue to live long after a single tree may fall or die.
In the case of Pando, this has led to over 47,000 genetically identical trees. These trees not only cover 106 acres of national forestland, but it is also estimated to weigh a shocking six million kilograms (13 million pounds). This makes it the most massive genetically distinct organism. However, the title for the largest organism goes to “the humongous fungus” a network of Dark honey fungus (Armillaria ostoyae) in Oregon that covers a shocking 2,200 acres.
Maybe even more impressive than Pando’s size is its age. Though it is difficult to know the exact age, Pando is estimated to be 80,000 years old! The oldest non-clonal tree in the world, a bristlecone pine named Methuselah, comes in at a mere 4,600 years.
Pando has managed to survive for so long by regularly replacing dead trees. This strategy makes aspen groves resilient to many natural disasters. When forest fires destroy the trees, aspens protect their roots underground. They can then return with force when conditions improve. In this way, the clonal aspen groves can achieve impressive longevity.
The older trees in Pando are around 130 years old. This is comparable to a normal Aspen’s lifespan. Soon, these trees will die. A healthy aspen grove can simply replace these dying trees with young saplings. As dying trees clear the canopy, more sunlight makes it to the forest floor, where young shoots can take advantage of the opening to rapidly grow. This keeps the forest eternally young, cycling through trees of all ages.
Though aspen groves are resilient to many destructive forces, ecological and environmental changes impact them. Human activity has encroached upon aspen groves in numerous ways. Ancient groves like Pando are facing changes over the last century that threaten their continued existence.
The ancient giant, Pando, has been shrinking since the 1960s or 70s. This timing is no coincidence. As human activity has grown in the western United States, so has our impact on the surrounding ecosystems.
The biggest factor causing Pando to shrink is a lack of “new recruits.” The shoots that form from Pando’s ancient rootstock are not making it to maturity. Instead, they are being eaten while they are still small, soft, and nutritious. Mule deer are the main culprits. Cattle are also allowed to browse in this forest for brief intervals every year. The combined herbivory has thwarted Pando’s efforts to keep up with old dying trees.
These changes have led to a thinning of the forest. A study published in PLOS ONE used aerial imagery over the past 40 years to identify these changes. With enough loss of old trees, the grove loses its ability to regenerate. A dense forest can fill its roots with fuel from photosynthesis, sending up new shoots regularly. However, as it loses leaves and photosynthetic ability, it risks rapidly shrinking.
Though it seems easy to blame these changes on deer, the real blame still lies with us humans. Throughout the 20th century, deer populations have been hugely impacted by humans. The hunting of apex predators such as wolves and mountain lions has allowed deer populations to grow unchecked. Though it is hotly contested by ranchers wanting to protect their cattle, wolf reintroduction is ongoing in the West.
Hunting is regulated by federal and state agencies, which artificially adjust deer populations. The consequences of these changes are not always immediately apparent. Forest managers do their best to replicate historical levels and manage new threats. However, we do not have historical data on herbivory in Pando and the surrounding area (or many managed areas.) What we do know is that Pando is not producing enough successful saplings to maintain its current size.
Though Pando is shrinking, efforts are already being made to reverse the damage. Adding fencing to areas of the forest will prevent herbivores from eating the fresh aspen shoots. The “exclosures” will give Pando time to establish large, healthy saplings that are not at risk of being eaten. Some areas that have been fenced off have grown 12-15 foot trees in just a few years. Controlling herbivory by increasing hunting is another option. Decreasing cattle grazing in the grove has also been suggested by researchers.
Aspens are extremely resilient and capable of surviving many disasters. However, a gradual change to the ecosystem can be harder to bounce back from. Human impacts on ecosystems are complex and far-reaching. It’s essential that we monitor all ecosystems to understand how they are responding to human activity. This is essential to minimizing damage.
Image Credit: US Forest Service