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I want to introduce you to two ancient organisms on different sides of the planet 鈥� one in the US, the other in New Zealand. Both are trees, both make us look at the world anew and I think both have lessons for us in the future. Pando, in Utah, is the world鈥檚 largest organism by dry weight 鈥� it鈥檚 a forest of thousands of trees, all genetically identical, connected by a vast root system. And T膩ne Mahuta is a giant kauri tree on New Zealand鈥檚 North Island. It鈥檚 2500 years old and has woven itself into the mythology of the M膩ori.

The god tree of New Zealand

I confess I鈥檇 not heard about kauri trees until recently, when I listened to a forthcoming album by the composer John Metcalfe. I knew he was a former member of the legendary Manchester band The Durutti Column, but I didn鈥檛 know that he was originally from New Zealand, and it was a visit to the North Island a few years ago to see its giant kauri tree that inspired his new recording. Tree is an homage to T膩ne Mahuta, which Metcalfe encountered and which moved him profoundly. 鈥淭here was something extraordinary about the atmosphere in the forest and the size of this tree, and the sense that it had been there a long time,鈥� he says. 鈥淚t was about the protection it gave, and the sense of connection we had with that protection.鈥�

I immediately wanted to learn more about T膩ne Mahuta, so I looked it up. It鈥檚 an incredible organism, 45 metres tall, reminding me both of the Tree of Souls in the movie Avatar but also, in its sheer scale, of the giant sequoia I鈥檝e seen in California.

T膩ne Mahuta is named for T膩ne, the M膩ori god of forests . There are many other kauri trees around it. Indeed, in the region of the island where it grows is a surviving sliver of what was once a large subtropical rainforest. The kauri tree (Agathis australis) is what ecologists call a foundation species 鈥� it has a promoting effect on the ecosystem by generating ecological niches for other species and increasing overall species diversity. It does this while also ensuring, through the action of its leaf litter on the soil, that it can outcompete other species trying to grow nearby.

Sadly, as we鈥檝e seen with many tree species in the northern hemisphere, kauri is under threat from a dieback disease that was only identified in 2006. It reminded me a little of some dieback-affected ancient yew trees in England, which I made a podcast about that you can listen to here. Unlike the yews, however, with kauri the disease is caused by a fungus-like pathogen (Phytophthora agathidicida). I got in touch with Mahajabeen Padamsee at Landcare Research, New Zealand鈥檚 Crown Research Institute for the land environment, who has been working on several projects to conserve kauri. She said there has been some work to introduce fungal species that form relationships with the tree roots into kauri seedlings, and specifically introducing species that can block out the pathogen. A big issue with efforts to protect remaining kauri, however, has been a lack of funding. The local M膩ori tribe, Te Kawerau 膩 Maki, is in favour of closing the forest to prevent tourists bringing in the pathogen on their shoes, but closures so far have been neither enforced nor effective. The pathogen has a track record of destruction: a sister species, Phytophthora infestans, causes potato blight, and is the agent that caused the terrible famines in Europe and Ireland in the 1840s.

I think we should follow the recommendation of the M膩ori here. For them, T膩ne Mahuta is a relative, and the kauri must be saved even if it means humans can鈥檛 enjoy the forest. Matt Hall at Victoria University of Wellington in New Zealand has worked on kauri restoration projects and also agrees. He says we need to let go of our ideas that the trees are there for us to go and relax under, and that, like the M膩ori, we should acknowledge them as intelligent, as kin, and let them be. I love forest bathing as much as anyone else, but sometimes it鈥檚 not about us 鈥� and it shouldn鈥檛 be.

A forest made of a single聽tree

A similar tale of threatened trees is happening on the other side of the world, in southern Utah. Specifically, a 43-hectare forest called the Pando aspen grove. Language immediately becomes limiting when trying to describe Pando 鈥� the mighty forest is a single tree. It鈥檚 a forest of more than 47,000 trees, yet they are all genetically identical outgrowths of the same organism, connected by a single root system underground. (You can listen to the sound of Pando on our podcast.)

Pando is the world鈥檚 largest organism by dry weight. It has been estimated it to clock in at nearly 6 million kilograms, or 6000 tonnes. That鈥檚 about 35 blue whales or 1000 elephants. It鈥檚 been regenerating for hundreds, maybe thousands of years too, making it one of the oldest organisms on Earth. Its cells are living and dying over time, but the DNA remains pretty much unchanged. That is, the individual lives on, even as its parts die. Some 2000 years ago, the Greek philosopher Plutarch wondered whether a ship that had its parts gradually replaced one by one was still the same ship when no original parts remained. Pando is biology鈥檚 Ship of Theseus 鈥� is it the same tree as when it first sprouted?

I spoke with Paul Rogers at Utah State University, who is the director of the Western Aspen Alliance and has worked on Pando for many years. Like the kauri trees in New Zealand, Pando is under threat. It is part of a national park but is being eaten by both wild mule deer and domestic cattle that graze there. New work from Rogers and others shows that the grazing is stopping the tree from growing properly and sending up new stems. The obvious solution, says Rogers, is to fence it off.

Even with deep familiarity, the wonder of standing within a huge single organism is continually awe-inspiring, he says. He enjoys that Pando blurs the lines between what an individual is and what a community is. And it goes beyond Pando into the wider ecosystem. 鈥淭hese aspen forests support myriad plants and animals,鈥� he says. 鈥淲here is the boundary when the system is so interlinked? It鈥檚 good for us humans to be humbled by challenging concepts, I think.鈥�

I think so too.