Quaking Aspen giant in Utah faces climate and wildlife threats

In the Wasatch Mountains of the western United States lies Pando, a 106-acre quaking aspen grove considered the largest single organism on Earth by mass. Although Pando is legally protected and not directly threatened by human activities, it faces risks from various natural factors.

"Pando," derived from the Latin word meaning "to spread," is located in Utah. At first glance, it resembles a forest made up of individual trees with characteristic white bark and small leaves that flutter even in the slightest breeze. In reality, it's a 106-acre complex of quaking aspen clones consisting of 47,000 genetically identical stems growing from a single, interconnected root network.

Most aspen clones in North America are much smaller, with those in the western United States typically covering only about 3 acres. Pando has existed for thousands of years, with some estimates suggesting it is as old as 14,000 years, even though individual stems live only about 130 years. Its extraordinary longevity and vastness have allowed an entire ecosystem, encompassing 68 plant species and numerous animals, to thrive in its shadow.

Scientists have estimated that the organism weighs around 6,000 short tons, making it the largest single organism on Earth by mass.

The entire ecosystem relies on the health of the Pando complex. Although it is protected by the US National Forest Service and not at risk of logging, its disappearance could result from several other factors.

As reported by ScienceAlert, one of the biggest threats to the complex is overgrazing by deer and elk. Wolves and cougars once kept their populations in check, but now the herds of these herbivores have increased. Additionally, animals often take shelter in Pando to avoid hunters.

The animals eat the tips of new stems, leading to plant death and restricted growth. This problem does not exist in the fenced area of the ecosystem. Decades ago, humans excluded moose and deer from a small area, allowing the organism to regenerate. The dense plant growth here is referred to as a "bamboo garden."

Elk and deer are not the only threats to Pando. Older stems are also attacked by at least three diseases: sooty bark canker, leaf spot, and conk fungus.

Although plant diseases have been present and evolving in aspen stands for centuries, their long-term impact on the ecosystem remains unknown. In particular, the lack of new shoots and a growing list of threats to this clonal giant raise serious concerns about its future.

The most serious threat, however, is climate change. Pando originated after the last ice age and has since thrived in a largely stable climate. Climate changes threaten the size and longevity of the tree, as well as the entire ecosystem it supports.

While no specific studies on Pando have been conducted yet, quaking aspens are threatened by climate changes such as reduced water resources and warmer springs, which hinder the production of new leaves. As competition for dwindling water resources increases, along with predictions of record summer temperatures and the risk of more intense wildfires, Pando will struggle to adapt to rapidly changing conditions and maintain its size.

Pando, the world's largest scientifically documented organism, has proven resilient to environmental changes since European settlement in the 19th century and increased recreational activity in the 20th century. It has faced diseases, fires, and grazing, and despite concerns about its future, scientists continue to discover the secrets of its resilience. The Forest Service is working to protect Pando and its ecosystem.