In his latest book, David George Haskell focused on 12 individual trees across the globe, from the Amazon to the streets of Manhattan. It gave him, he says in a Yale e360 interview, a profound sense of the complex networks that sustain life.

David George Haskell is nothing if not a patient observer. In the course of one year, he stood watch over a single square meter of old-growth forest in Sewanee, Tennessee, where he teaches biology and environmental studies at the University of the South. Those observations resulted in Haskell’s first book, The Forest Unseen, which was a finalist for the Pulitzer Prize in 2013.

In his latest book, The Songs of Trees, Haskell takes those powers of observation and uses them to lyrically describe repeated visits to 12 trees around the world, including a ceibo in the Amazon rain forest in Ecuador, a pear tree on the Upper West Side of Manhattan, and an olive tree in Jerusalem.

David George Haskell

David George Haskell

In an interview with Yale Environment 360, Haskell explains that, in writing the book, he wanted to explore not only individual trees, but their connections to the biological networks around them, including humans, and the often-unheard sounds that result from these interactions, from a beetle chewing the inside of a dead ash tree to waves washing over the roots of a palm tree. “There is no such thing as an individual within biology,” says Haskell. “Instead, the fundamental unit of life is interconnection and relationship … Without interconnection life ends.”

Yale Environment 360: When you first had inklings of this book in your mind, how did you think about it? What did you want to communicate?

David George Haskell: I’ve come to realize that trees have all sorts of sounds within them and coming from them and sounds wrapped into their community life, sounds of both plants and animals, including the human animal. And I wanted to explore those sounds and see what sort of story those sounds would lead me to. Part of the origin of the book came from literally just listening, opening my ears. 

“Trees are such massive beings and so long-lived that they really are extraordinary examples of interconnection and of belonging within a place.”

The second pathway that led into the book was wanting to explore some ideas that I’d started discussing in The Forest Unseen, my first book, ideas about what it means for humans to belong within the community of life, to belong here as evolved creatures like every other creature on the planet. What does that mean for our understanding of how we see ourselves in that community, what our ethical responsibilities might be? Trees are such massive beings and so long-lived that they really are extraordinary examples of interconnection and of belonging within a place. So I wanted to use them as windows into these larger questions about ecology, evolution, and ethics.

e360: In the book you write about repeatedly visiting a dozen trees throughout the world. Why those 12?

The view from the crown of the ceibo tree that Haskell visited multiple times in the Amazon.

The view from the crown of the ceibo tree that Haskell visited multiple times in the Amazon. David George Haskell

Haskell: The first thing to say about that is that these trees are not meant to be representative samples, nor do I claim to have any sort of universality here. Instead, I was looking for trees where there was an interesting convergence of ideas and of stories. Some of these trees were ones that I’d encountered previously on my travels. The tree in Ecuador, for example, is a tree that I’d visited many years ago, and it left a very deep impression on me. The tree in New York City is a tree that I started sitting with and listening to during my visits for conferences, lectures, and meetings in the city. I wanted to understand the biology, the ecology of the city through the life of a tree.

The last category of trees are ones that I had not yet encountered, but once I started the book, I knew that, “OK, I’m going to go to the West Bank in Jerusalem and find a tree there to sit with and to listen to and talk to people about.”

e360: You mentioned the tree in Ecuador, the ceibo tree. It grows in the Yasuní Biosphere Reserve. You write that, “Dissolution of individuality into relationship is how the ceibo and all its community survive the rigors of the forest.” How so? 

Haskell: The Amazon rainforest is a place of great competition and conflict, it’s a place full of pathogens and competitors and parasites. So how does an organism make it through that? In the past in biology, we have turned to atomism for an answer… meaning that the individual is the fundamental unit of ecology and evolution. Individuals have to fight it out, individuals have to find evolutionary solutions through natural selection. That’s a very powerful view, and it helps us understand the world in many ways.

“Life persists through connecting with other life forms to find solutions to particular problems.”

There’s a complementary view, which is that the individual is in fact an illusion. It doesn’t exist. There is no such thing as an individual within biology. Instead the fundamental unit of life is interconnection and relationship. That sounds like it’s edging into mysticism, but I don’t mean that in a mystical way at all. I mean it in a very practical way at the level of genetics and biochemistry and microbiology and ecology, that without interconnection, life ends. And in the rigors of the Amazon rainforest and in the rigors of other ecosystems, life persists through connecting with other life forms to find solutions to particular problems.

The ceibo tree is interconnected with thousands of other species, and without those connections the ceibo could not live. If, say, the genetic connections between the bacteria around tree roots are severed, or if the fungi and bacteria that live within leaves are removed, the tree can’t deal with drought, it can’t fight off pathogens, it can’t process nutrients from the soil. Interconnection is fundamental to life.

e360: The Waorani, the indigenous people who live in the reserve, make use of the ceibo by turning it into … you use the word sub-woofer. Tell me about that.

Haskell: The ceibo in the Waorani cultures is known as the “tree of life.” It’s present in the creation story, it has many uses within the culture. One of those uses is as a way of signaling across long distances in the forest, and Waorani do this by pounding on the buttress roots of the tree. The tree is very tall and like many other trees in the rainforest it has these sheet-like buttress roots that come out from the main trunk out into the forest. They’re like great big planks of wood and when you pound on them, the pounding results in a great reverberation within the buttress roots, that does sound like a sub-woofer, a very, very low thump.

Those low frequencies pass through the forest unimpeded. If people get lost in the forest they can pound on the tree and other people will hear and be able to come and find them.          

e360: You observed a green ash tree in Tennessee. You came across it right after it fell, and visited it for two years. You write that, “Death decenters the tree’s life, but does not end it.” It does seem from your writing that a decaying tree is just as interesting to observe, if not more so, than a living one.

Haskell: Yes. Of all the trees that I visited this is the one that surprised me the most. I knew there would be some interesting things happening with a fallen tree, but I didn’t realize how much life gathers around a big fallen dead log. I understood that in the abstract, perhaps, but to go there again and again, dozens and dozens of times, and on every visit to see some new creature that’s making use of this tree or some new phenomenon emerging from the tree itself was just extraordinary. So indeed, in life a tree is a network of connections, and the tree is in control of some of those connections, [but] then after a tree falls, gradually, that control ebbs away. The tree is no longer an active participant at a genetic level, but there is still an extraordinary network of life that’s probably just as rich and diverse as the network of life in the tree while it was standing.

e360: You use a range of listening devices on these trees. For instance, you put a stethoscope to that dead tree. You use small ultrasonic sensors on ponderosa pines and on a tree on the Upper West Side of Manhattan. What were you listening for?

Haskell: I used a multiplicity of approaches to see what was there to explore, what can one hear with the stethoscope compared to with just one’s unaided ears? What can one hear through one’s fingertips by resting a hand on a tree trunk during the wind? Then, of course, microphones and electronic sensors reveal sounds and vibrations that are not available to our unaided years. Through those sounds I was trying to seek some of the hidden stories, some of the hidden connections, and some of the drama. For example, an ultrasonic detector applied to a tree, particularly in the summertime, reveals how as the morning passes into afternoon, the tree goes from a state of full hydration to a place of distress, where there are all sorts of little ultrasonic clicks and fizzles emerging from the inside of the tree as water columns break, as the tree becomes more dried out. By applying an ultrasonic sensor, the tree suddenly has its inner life revealed.

e360: You venture into the heart of the Upper West Side of Manhattan to observe a Callery pear tree at the corner of 86th and Broadway. You write that, “This tree is hardy and well-suited for city life,” but you also say that, “A tree planted by its human neighbors will live longer than one planted by an anonymous contractor.” Tell me more about that.

Haskell: Many trees in urban areas are of course selected for their adaptability to urban areas. This one, the Callery pear, comes from China, where it grows on some rather hostile soil. It’s well adapted to drought and to heavy metals and a certain amount of salt in the soil, all things that will help it survive in the city. But often, this isn’t enough. There are all sorts of [other] challenges. Dog poop, people chaining their bikes, and hitting the tree with their cars, and so forth. So for many trees, it’s basically a 50/50 proposition whether the tree will live through its first 10 years.

Haskell repeatedly visited this Callery pear tree in Manhattan, shown here in full bloom.

Haskell repeatedly visited this Callery pear tree in Manhattan, shown here in full bloom. George David Haskell

But, if the tree is planted with the help of the people who live on the city block, and if the tree has a little tag on it saying, “Hi, this is my name. I’m a Callery pear. I’d appreciate some water if it’s a hot dry summer. Please don’t let your dog poop here. Please, please watch out for my bark.” All these things give that tree membership within the human community. The probability of survival for that tree goes way up closer to 100 percent in some cases because people are then looking out for that tree.

e360: You observe that New Yorkers echo in their own way Amazonian Waorani when it comes to feelings about trees. What did you see to convince you of that?

Haskell: People often have very deep relationships with trees, particularly people who’ve lived in a particular place for a long time and have grown up with a particular tree. This is true in the olive groves of the West Bank, just as it is in the Amazon or in New York City.  This tree becomes part of our narrative of place and who we are. When I talked to people in the city about trees on their blocks, often it’s a topic that really animates the conversation. So when the few examples of that heritage are taken away from us, we really feel a deep sense of loss. 

“People often have very deep relationships with trees, particularly people who’ve lived in a particular place for a long time and have grown up with a particular tree.”

Now, that isn’t universally true, of course. There are places in the city where trees are neglected, where people have other things on their mind, and those are city blocks in which trees don’t thrive. In Harlem, there are city blocks where there are beautiful trees that are well cared for and loved, and then there are places where the trees struggle. Those tend to be the same places where people are struggling, where the physical environment is very challenging for both people and trees. There’s some psychological literature about this. One way of enhancing both human well-being and the well-being of other species in the city is by promoting healthy growth of trees and promoting connections of trees to people.

That’s true at a global level of course, as well. We’re losing hundreds of thousands of acres of forest. In the first 12 years of the millennium, we lost 2.3 million square kilometers of forest, and only 800,000 regrew. That is an important fact when we’re looking forward into the human future. Will we thrive on this planet? That question is tied to [whether] forests thrive. So what’s true on the city block at a very micro scale is also true at a planetary scale.