Pando: the aspen colony that might be the oldest known living organism


Nature doesn’t have to be horrible. I know that’s a weird thing to say at Secret Base, where we have enjoyed exploding ants, tongue-chomping parasites and trees that kill birds for the lols. But evolution has produced some curiosities that aren’t a combination of bizarre and heinous, and perhaps it’s time to lighten up with a discussion of one of the most impressive curiosities of all: Pando.

Pando is possibly the oldest, heaviest living thing on Earth. These things are difficult to determine; it’s definitely one of both. It lives in Fishlake National Forest, and is a quaking aspen. Sort of.

Quaking aspen in Colorado (not Pando)

Because we live on the macro scale, we’re used to thinking of living being as discrete entities. A person is a person, a dog is a dog, and a tree is a tree. But, as we encountered with our exploding ants, that’s not always the most sensible way of understanding the natural world, which tends to be at least a little indifferent to the entire concept of individualism.

The oldest individual trees in the world are California’s bristlecone pines, windblown* subalpine conifers which can live for thousands of years. The oldest known living specimen, ‘Methuselah,’ has been verified at a staggering 4,852 years old. No matter how you slice it, this is an impressive figure, and while it’s abnormally high for a bristlecone there are plenty around only a couple millennia younger.

*Fun fact: there’s a word for the weird, wind-sculpted trees that you see on shorelines or mountains. They’re called krummholz trees, and they are gorgeous.

Pando, meanwhile, is significantly older. Until recently, rough estimates had it at something like 80,000 years old; this has been revised down significantly in light of the fact that the area of Utah in which it lives was covered by an ice sheet 20,000 years ago, a problem even the most badass tree would have trouble surviving. Pando’s now clocking in at a mere 15,000 or so.

Unlike the bristlecones, which can be dated accurately through tree rings, it’s pretty hard to get a fix on Pando’s exact age. This is because Pando is a tree colony. Quaking aspens have the curious property of being able to reproduce themselves clonally, sending up new seedlings from their roots. These ‘ramets’ function, for all intents and purposes, as baby trees, living and dying just like you’d expect any stand-alone aspen to.

But they’re all the same organism. Pando is a 13 million pound collective of more than 40,000 stems, genetically identical and all grown from the same massive (100+ acres, easily) root system. It cares about individual stems just about as much the average person might fuss about individual hairs on their head.

How does anyone know any of this? How can they begin to guess at Pando’s biology? Establishing the genetic identity of the trees is fairly straightforward these days, but the whole colony? As it turns out, quaking aspen have an extremely hard time reproducing through non-clonal in the American West, where the climate turned unfavorable several thousands years ago. As Mitton and Grant justified the age estimate in their 1996 paper, “Genetic Variation and the Natural History of Quaking Aspen”:

Part of the rationale behind current age estimates for aspen clones is that sexual reproduction is effectively frustrated by the rareity of a favorable suite of conditions in semiarid environments. Clonal age, in the strictest sense, truly applies only to the individual genome, which is the single element of clone identity that would be continous across such time spans. … Perhaps DNA sequence data from various parts of the clone could be used to estimate age from the accumulation of mutations.

As far as I could find out, that last study has not actually been executed, but given the conditions in which Pando lives it’s very, very clear that it’s an extraordinarily ancient organism. And it’s not just ancient — while bristlecone pines are studies in endurance in the face of deep time, Pando’s a very different story. Instead of fortitude, it invokes dynamism. Decadent stasis might be an interesting fantasy, but nature is built from Pandos, systems that masquerade as individuals and persist into what might as well be eternity.

If the theories of the origins of life I was taught at university are correct, some billions of years ago, a chemical cell in a deep-sea volcano managed to bud off a copy of itself, and has echoed its way to chaotic, confounding immortality. The entire biosphere is, in some ways, a Pando, genetically drifting its barely-perceptible way to quaking aspens, tongue-eating lice and us.

Humanity is only just beginning to understand how biology actually operates. Darwinian evolution is 160 years old, and the structure of DNA was only determined in the early 1950s. Hell, Antonie van Leeuwenhoek’s discovery of microscopic life was less than four centuries ago. For most of Pando’s thousands of years existence, humans wouldn’t even have been able to recognize it. They’d literally miss the forest for the trees.

There’s something profound in that emergent reality. There’s also something perverse there too. Since the 80s, Pando seems to be struggling, unable to bring its ramets to maturity fast enough to replace falling stems. In 2019, Rodgers and Šebesta produced this uneasy paragraph:

While it is clear the base cause of the current trajectory is not mature tree mortality, but chronic browsing of regenerating aspen suckers, we are left wondering how this iconic organism survived and thrived likely for millennia—the exact age is unknown—while it appears to be dwindling suddenly during our time. Changes in ungulate herbivore management over recent decades provides the most plausible explanation, though exacerbating agents, such as increased human presence and warming/drying climatic conditions likely play a role. Collectively, both direct and indirect human impacts are negatively influencing Pando.

We live in the first age that is able to grope its way back towards the true mysteries of biology. We also live in an age that seems preternaturally gifted at disrupting that biology, and in a civilization that only barely cares about the consequences.

Pando will probably get along ok — we don’t let celebrities go that easy. We can fence off regions to prevent overgrazing of young stems, that sort of thing. But a Pando is just a Pando; without taking better care of the supra-organizational systems that support these miracles … we’ll end up killing many of them off just as we’re learning to appreciate them.



Source link

Leave a Reply

Your email address will not be published. Required fields are marked *