Excerpt: Jared Farmer on the World's Longest Living Organisms
In the latest issue of LA+, the historian talks to Editor in Chief Karen M'Closkey about place-based planetary history.
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For LA+ BOTANIC, the latest issue of LA+, the interdisciplinary landscape architectural journal of the Weitzman School, Jared Farmer, the Walter H. Annenberg Professor of History at Penn, talks about his latest book, Elderflora: A Modern History of Ancient Trees. In a conversation with Karen M’Closkey, associate professor of landscape architecture and editor in chief of the journal, he explores the lessons that some of the world’s longest living organisms offer us in the face of rapid climate change.
You have described your work as “place-based planetary history,” which sounds contradictory. Can you explain what that means and how trees were a medium through which to approach history in this way?
It’s meant to sound paradoxical. No single person can possibly “do” planetary history, but I wanted to write a book about the most important issue of our time, which is climate change, and the scale of that is in fact the planet. Planetary history is different than “global history” and “world history,” terms that have been around for decades. World history generally means large-scale geopolitical history, while global history covers processes of globalization, including geopolitics, though these two approaches have somewhat different theoretical bases. Global history is weighted toward the modern period—the consequences of the Columbian Exchange, the Atlantic slave trade, Western imperialism, settler colonialism, capitalism, industrialism, and so on. Planetary history encompasses all of that, and more. It is more than human. It foregrounds nonhuman things because people are now planetary agents who are altering the biosphere and evolution itself—and yet they’re not the only changemakers at that scale. They’re actually late to the game. Plants have been changing the biosphere a lot longer than humans. So, the story must start millions of years before the modern period. Even though climate change has accelerated in recent centuries and decades, the planet has been through many different climate regimes in its deep history.
I do think trees are one of the best ways to get at planetary history. Woody plants, especially gymnosperms like conifers, come from incredibly old genetic lineages. They’ve lived through many planets, one place at a time. Each organism is rooted in place for the entirety of its life. Trees are the most place-based of all organisms because their commitment to the local is absolute. And yet they live almost their entire lives outside the favorable climate conditions of their germination. Trees are experts in living out of time while showing resilience in place. They’re useful to think with by analogy as we confront climate change. We all now live outside our birth climate, even if we’re young — maybe especially if we’re young.
Dendrochronology—the science of reading tree rings—is so familiar from grade-school science class, it’s easy to forget how remarkable it is that humans figured out we can read climate this way. Has the science of dendrochronology changed much in the last few decades, or have there been technological advances that have changed what we thought we knew?
A lot of people assume that tree-ring science must be easy because it means counting rings; they’re surprised to learn it was institutionalized so late, in the 20th century. It’s actually a very technical and difficult interdisciplinary field concerned with the interpretation of data in cambium layers after they’ve been dated.
Going back thousands of years, people noticed that woody plants produce growth layers. The notion that these could be annual markers is also pretty old. Leonardo da Vinci was one of the first people to write about it; there were some German naturalists in the 19th century who thought about whether cambium layers in the temperate zone could be read as records of annual weather, and Henry David Thoreau was fascinated by tree-rings and journaled about them. But it wasn’t until an early 20th-century astronomer, Andrew Ellicott Douglass, began thinking about the possible biological effects of the sunspot cycle that dendrochronology came into being. Douglass’s technique involved much more than counting rings. It was about connecting rings from different trees and creating networks of samples that shared common signals that could be used as proxy data for environmental phenomena. You need the right trees in the right places to create a cross-dated network; and to pull out all your core samples, you need an increment borer, a tool that wasn’t invented until the 19th century.
Certain conifers living in certain ecotones produce the most sensitive rings, and therefore the most reliable data with the least noise. It turns out that the American West—Douglass worked at the University of Arizona—was ideal for tree-ring science because it’s a land of mountain conifers. Here Douglass and his protégé Edmund Schulman found members of the cypress and pine families growing in rugged, semiarid habitats, living in feast-or-famine conditions, depending on whether it rained each summer, and their tree-rings responded in an exaggerated way to precipitation or temperature signals. Within several square miles of steep terrain, they might locate discrete populations that allowed them to get corresponding data samples going back thousands of years. Though Douglass was never able to prove that the sunspot cycle had an effect on tree growth, his cross-dating technique became indispensable to archaeology (for dating architectural structures) and later to climatology.
In your book Elderflora, you reference Pliny’s Natural History (77 CE), which you describe as the “oldest extant list of oldest trees in the world.” Does this mean that the identification of elderflora is not a recent scientific quest? Or how have the reasons for this ambition to identify elderflora changed?
It’s an ancient quest that changed in the modern period. Pliny and other naturalists in the prescientific era emphasized what I call “relational age”; that is, the oldest tree was as old as a city, or as old as a temple. It wasn’t necessary to know exactly what year the tree germinated, or exactly what year the temple or the city was built. Rather, the relationship between the tree and the built environment was the important thing. A consecrated tree could die and be replaced with an offshoot, and effectively live on as the same plant. The “tree” was in fact a relationship between people, a cultural tradition, a built landscape, and a vegetal germplasm. This relationship in place embodied cyclical time. Fast forward to the 18th century, and the whole epistemology begins to change. Now, scientists and foresters want to know exactly how old an individual tree is based on its cambium layers. Each tree-ring has an exact date or no date. I call this “cambial age.” Because of dendrochronology, we now know the precise ages and locations of hundreds of millennial trees –this despite the incredible deforestation of the industrial period, often in combination with settler-colonial land clearance. These surviving plants are irreplaceable by nature: once they die, they are dead, and cannot be replanted. They represent linear time and the terminal nature of modernity. Many of them have become de facto sacred sites. One of the main themes of my book is this recapitulation of modern science and premodern religion. I’m struck by the correspondence between the consecrated trees of the ancient world—sacred because of their purported age in relation to human landscapes—and these more recent “secular sacred trees,” which are sanctified by science and guarded not by priests but by park rangers. They’re protected because technicians have determined they are old beyond a certain number of years — 1,000 — significant to rationalists and religionists alike.
On the one hand, I’m moved by, and I celebrate, continuity in human history across periods, across cultures, as exemplified by this desire to identify and venerate slow plants. On the other hand, I find something disturbing in the modern obsession with quantifying the oldest, the biggest, the thickest, the tallest. All those 19thcentury naturalists traipsing the globe with measuring tapes can seem silly, but my discomfort runs much deeper. It has to do with our numerically obsessed culture and its privileging of things that can and must be counted and datafied, faster and faster. Science is now one of the leading forms of meaning in the world. In this worldview, if something — including a tree — cannot be datified, does it have no value?
You’ve described trees as “living bridges” between past, present, and future, but have commented that humans have a great ability to think of the deep past but are bad at thinking of our long-term future. Obviously, trees help us understand the past — we’ve discussed dendrochronology — but how can they help us think about the deep future beyond their role as carbon sinks?
In the process of writing my book, I grew really weary of people saying, “We just need to plant more trees,” which strikes me as ludicrously wishful thinking and implicitly offensive, as if woody plants are nothing more than carbon sequestration devices for our instrumental use. I also got tired of hearing this: “We just need more climate data and then people will finally act.” Lack of data is not the problem! It’s a collective action problem. It’s a political problem. It’s an ethical problem. The multi-disciplinary science behind climate modeling was one of the great accomplishments of 20th-century science, but, at this point, politically speaking, we don’t need any more data. Tree-ring archives are melancholy spaces — though they do smell heavenly — because the past recorded in the wood samples is no longer a reliable guide to the future. When these collections were established in the 20th century, the idea was to use tree rings to predict climate cycles. That’s now impossible. You can still do amazing things with tree rings, as shown by the recent dating of stellar proton events and supervolcanic eruptions, but the climate of these data-recording trees is obsolete.
Likewise, it’s undeniable that all the oldest surviving trees of the Holocene will die before their time. They will perish in cohorts and they cannot be replaced, even with cloning, because they have cambial age rather than relational age – though I suppose you could say their mortality is relational to the Anthropocene.
Pronouncing that ancient trees are going to die prematurely is not the same as predicting that tree species will go extinct. Some long-lived species, especially in the conifer division, are in big trouble; others aren’t. But there will be a loss of oldness as measured by science. I anticipate an interregnum when most people on the planet will not have easy access to trees absolutely known to be 1,000 years old or older. That’s something — an extinction of experience — to mourn. But that’s different from saying that there won’t be, or can’t be, old trees in the future. We need to care for the future oldest trees; we need to design for trees with a future. That’s why I’m interested in premodern, prescientific traditions of venerating old trees. I think we need to go back to practices of venerating old things in a relational sense, within built environments. When thinking about the deep future, it often helps to consider the ancient past.
