At first glance, Pando is unimpressive. If you aren’t looking for it, you could easily drive past the homogenous forest of stems ranging from a few inches to some 100 feet (about 30 meters) tall—the biggest they appear more like trunks—all with matching leaves, on one of the few roads leading to Fish Lake in southern Utah.

But if you do pull over on your way up to the lake, and give it more than a second’s look, you might recognize that you’re standing in front of world’s largest living organism, a colony of over 47,000 identical, quaking aspen trees, all connected by a single root system spanning over 100 acres. Scientists believe it to be the world’s largest single organism. When my partner and I stopped in front of part of it last week, Pando’s leaves had all turned yellow for the fall. It was snowing and serene, and both a humble and humbling sight.

Benjamin Daniels Walking in Pando.

Scientists aren’t sure how long Pando has been alive, but estimates that place its birth somewhere between 80,000 years and over a million years ago. Individual stems can live longer than 130 years. The death of one stem signals to the root system that it’s time to grow another. Like the hairs on our heads, the ages of each identical stem vary, so the colony remains robust even if a few die.

And yet, its days may be dwindling. A recent study from Utah ecologists suggests that for the past 40 years or so, Pando hasn’t been able to regrow its stems effectively.

“People are at the center of that failure,” Paul Rogers, an ecologist Utah State University who co-authored the paper, told Earther. Nearby ranchers have allowed their cattle to roam and snacked voraciously on young stems, and as human populations have grown in the area, deer hunting has decreased for safety reasons. But thriving deer populations wreck havoc on young aspen stems. For the past 40 years, it appears the root system has not been able to reproduce fast enough to keep up with the decimation.

Rogers and Darren McAvoy, also at Utah State University, studied aerial footage of the tree system dating back to 1939, and saw that clearing aspen stems for human development has cause Pando to stop regrowing in some areas for three to four decades. They also surveyed parts of Pando from 2016 to 2017 to look at the overall health of the tree, and used scat as evidence of deer and cattle intrusion.

A few areas of Pando were experimentally enclosed in fences in 2013 and 2014; these showed signs of much healthier regrowth. To help Pando survive the long haul, humans will need to set up more thorough and better fencing, cull some of the deer, and make sure cattle aren’t grazing in the area, Rogers told the New York Times (paywall).

Saving Pando would be a feat for conservation; if scientists are able to protect this one colony, they’ll be likely be able to use similar tactics to protect other endangered forest ecosystems. On the other hand, its death would be a massive failure to protect one of Earth’s remarkable forms of life, which has existed for longer than modern humanity.

Correction: An earlier version of this article incorrectly referred in one instance to Pando as a system of cedar trees. It’s a system of aspen trees.