The 47,000 Trees That Are All One Tree

In 1976, ecologists Jerry Kemperman and Burton Barnes walked through a 106-acre stand of quaking aspen in Utah's Fishlake National Forest and concluded it was one tree. Roughly 47,000 stems, all genetically identical, all connected at the root. They named it Pando — Latin for I spread.

Pando weighs roughly 6,000 metric tons, spread across an area larger than 80 American football fields, which makes it the heaviest known organism on the planet. Its age is harder to pin down, since you cannot core a clonal organism that has no single trunk. Estimates cluster between 16,000 and 80,000 years.

Pando is dying. The cause is not climate or pathogen. It's mule deer.

Aspens reproduce mostly by sending up shoots from the root system — suckers. For decades, deer and elk on the Fishlake plateau have eaten those suckers before they grow into stems. The canopy ages and nothing comes up to replace it. A 2018 PLOS One paper led by Paul Rogers at Utah State University walked the clone in detail and showed that outside fenced enclosures, new growth cannot mature. Inside the fences, it does.

The Forest Service began fencing sections in 1993 and has expanded the project since. Predators that once kept the herds smaller — wolves, more cougars — are mostly gone. The deer are protected and locally fed.

Whatever Pando turns out to be at the high end of the age range, an organism that may have outlasted the last ice age is being held together by wire mesh.