Trees

Stump: 

[sounds of walking in the woods] Back to trees

Richter: 

Yes Trees Definitely. 

Stump: 

Can I ask a couple of philosophical questions?

Richter: 

Yeah. And the forest we’re about to walk into is why I wanted us to go to—

Stump: 

We’re going to walk into a different forest than we’re in currently? So this is one of my questions. It wasn’t the one I was going to ask. [laughter]

Hoogerwerf: 

Welcome to Language of God. I’m Colin Hoogerwerf. 

Stump: 

And I’m Jim Stump, resisting the urge to make all kinds of jokes about my last name and the content of this episode.

Hoogerwerf: 

I support you in resisting that! We’re here in the studio, but we’ll eventually find our way back to the woods and that philosophy question that you were about to ask. 

Stump: 

In case listeners are worried about an episode on the philosophy of trees, we did more than just philosophy in the woods. We also saw a bunch of cool trees.

Richter: 

The bigger trees are liriodendron here. Tulips, poplars…

Foerster: 

I always considered Ash trees to be a great blue collar tree. 

Davis: 

The pomegranate is the symbol of life in Israel.

Boogaart:

 There’s some huge oaks on the other side; you can see one of them there. 

Li: 

Probably three of our species are really, really common––the sugar maple one, also the oak. We also have, of course, the beech trees. 

Hoogerwerf: 

Longtime listeners might be starting to put together a pattern with some of these episodes. In episode 4 we talked about soil.

Stump: 

And then you did an episode about water. 

Hoogerwerf: 

Yeah, and I’ve had this episode in mind for a long time, following the same kind of pattern as those other ones. So over the last couple of years, we have taken walks with a bunch of different people, some of whose voices we just heard, through different forests talking about trees. And I have to say, this episode was slow in coming together. I think I could have just kept doing interviews and going on walks through the woods, waiting for the trees to tell me what story to tell. The ancient Israelites seemed to have a better ear for the voice of trees—

Stump: 

We’ll get to that.

Hoogerwerf: 

—The trees seemed to be pretty uninterested in talking to me, though maybe they occasionally clapped their hands? But eventually here’s what I came to realize: I think that maybe I’ve been thinking about trees all wrong, or in a lot of cases just not thinking about them at all; and I think that’s true for a lot of other people too. If we do think much about trees, it is usually as silent, immovable, pieces of the scenery. I know trees are alive, but I’ve come to realize that I don’t often give much thought to what that means. But when we start to learn more about trees, God’s world seems to become more complex, more interesting, and it becomes more alive. 

Stump: 

We’ve talked before on the podcast about seeing as, this idea that what we believe about something changes how we perceive it. For trees, it wasn’t all that long ago that I was one of those who didn’t think about trees much at all. I didn’t have any names for them and didn’t pay much attention. And so I didn’t see trees as distinct from one another. 

Hoogerwerf:

My grandpa, when he got a bit more cantankerous in his later years, used to say “A rock is a rock, a tree is a tree” in response to my grandma’s very adventurous travel proposals. Essentially saying if you’ve seen one, you’ve seen ‘em all. 

Stump: 

Exactly. That’s essentially where I was, though perhaps without the cantankerousness. But somewhere along the way, I decided I wanted to change that. So I got my Sibley’s Tree Guide at your recommendation, and started to train myself to see differently. 

Hoogerwerf: 

And the results?

Stump: 

I do see differently. There’s a philosopher William James who described a baby’s experience of the world before any language of rationality as “a blooming and buzzing confusion.” And that’s a little bit how I felt. I think I’ve come to a spot where a tree is not just a tree. I notice the differences in leaves and bark. I know some names. It feels a little bit like there are a bunch of new friends around that I didn’t even know were there before when I’d go out for a walk. But I still don’t have enough categories to really make total sense out of it all. Your tree story goes back further than mine, though.

Hoogerwerf: 

Yeah, I remember learning the names of the trees in my yard from my dad when I was a kid. I was always amazed that the other kids in school didn’t know the difference between oaks and maples. And since then I’ve spent some considerable time studying trees, both academically and as a hobby. But I’m also just starting to learn some things about trees that are pushing me further along, like when I learn about how trees interact with the world in ways that really force me to change some of the categories I had put in place. 

Stump: 

So we could think about this episode as a journey to see trees more completely, a journey which all of us come to from different points; and maybe our listeners will leave a little further along in that journey. 

Hoogerwerf: 

And the results of that might be more than just increasing our Latin name vocabulary, though I’m a big proponent of doing that. Besides revealing more about God’s world, learning about trees might also reveal something about God’s Word. 

Stump: 

Yeah, trees are pretty prevalent in the Bible. We’ve got the Tree of Life, and the Tree of the Knowledge of Good and Evil, and presumably a garden full of other trees. 

Hoogerwerf: 

There are the cedars of Lebanon and the acacia trees, which were used to build the tabernacle. 

Stump: 

Zaccheaus climbed a sycamore tree. 

Hoogerwerf: 

Quick side note. The Zaccheaus’ sycamore was probably a sycamore fig, Ficus sycomorus as opposed to the sycamore out my window, the one North Americans will know, Platanus occidentalis. But anyway…Jesus talks about the mustard tree, and he even calls himself the vine––which maybe isn’t a tree, per se, but not too far off. 

Stump: 

Righteous people in Psalm 1 are “like trees planted by streams of water.” Of course, Jesus also died on a tree. And then in John’s vision in Revelation, we see the Tree of Life again at the center of the new heavenly city, bearing 12 kinds of fruit? 

Hoogerwerf: 

Yeah. I’m afraid dendrologists might be frowning thinking about a tree that produces twelve different kinds of fruit. Clearly trees were symbolic and were important to many of the stories in the Bible. So understanding trees as symbols I think can help us to better understand what the biblical authors were trying to tell us. 

Stump: 

Seeing trees as something else in these symbolic ways has to start with the actual physical reality of what they are: xylem, phloem, cellulose, and lignin. Did I get those right? 

Hoogerwerf: 

Yep, those are things in trees. 

Stump: 

And it turns out that the non-symbolic existence of trees is pretty important to life on earth.

Hoogerwerf: 

Let’s start there. Here’s the plan. We’re going to explore the non-symbolic importance of trees, starting about 400 million years ago. Don’t worry; we’ll move quickly up to the present, and we’ll try to put in place some of those categories you were looking for about where trees came from. 

Stump: 

A family tree for trees?

Hoogerwerf: 

Yeah. And that will prime us, I think, to move into the symbolic world to see what emerges from the trees in the Bible. 

[transition music]

Hoogerwerf: 

As we said, trees came on the scene of earth about 400 million years ago. But they didn’t look much like our trees today. 

Stump: 

This is before vertebrates have come to land yet, so the whole world looks pretty different. 

Hoogerwerf: 

And the trees have a lot to do with some of the changes that happen around this time. Photosynthesis from trees starts pumping oxygen into the air and taking carbon dioxide out of the air and turning it into plant material. Roots snake into the ground, changing the chemistry, securing the ground from erosion. And when the plants die, all that carbon they’ve been storing up gets buried in the newly created soil, much of what we’re burning now as fossil fuels. 

Stump: 

The trees and plants also open up all kinds of new possibilities for animals, as food and as shelter. By 250 million years ago, the planet has changed from something that would be almost unrecognizable to something close to what we might be familiar with today. 

Hoogerwerf: 

The trees we have today all come from an evolutionary line out of the devonian and carboniferous periods. The earliest trees––those ones from 400 million years ago––were actually more closely related to today’s mosses and ferns. They reproduced by spores, not by seeds, and nothing like that exists in tree form any more. Today’s trees all come from the gymnosperms, the first seed producing plants, and the angiosperms, which also reproduce by seeds and came about a little later in evolutionary history.

Stump: 

Gymnosperm, with gymno, I remember from Greek class, means “naked,” and sperm referring to the seed. I don’t remember angio, but I’m guessing it’s somehow different than “naked”…maybe “clothed,” somehow?

Hoogerwerf: 

Yeah, so I looked it up and angio means container. And so you can think of seeds like apple seeds or other fruit seeds that are surrounded by flesh, or nuts which have husks and shells. Technically, they are seeds that form enclosed within an ovary. The obvious example of a gymnosperm seed is a seed in a cone, like a pine cone. Gymnosperms seeds develop on the surface of a scale or a leaf. 

Stump: 

OK, so gymnosperms and angiosperms are the two historical groups from which our trees today evolved. But it gets more complicated to sort out the contemporary divisions of trees.

Hoogerwerf: 

Yes. All our trees today are either gymnosperms or angiosperms. But there are other plants in those groups too. So all trees, of course, are plants; but not all plants are trees. 

Stump: 

I love it when you talk logic to me. How about some necessary and sufficient conditions? What does it take for something to be a tree?

Hoogerwerf: 

So you’re probably going to find a few different definitions. But some necessary conditions would be that it has to be perennial, with an elongated, woody stem, and probably with branches. Some definitions might have a height requirement. But to put trees in their place, let’s start with plants as a whole:

Li: 

When we think about plants, we think about, just, you know, four major groups.

Hoogerwerf: 

This is professor Jianhua Li.

Li: 

I’m a professor in the biology department and also a T. Elliot Weier Professor of Plant Science

Hoogerwerf: 

Dr Li teaches at my alma mater, Hope College; and we took a walk through woods at Hope’s ecosystem preserve, out by the sand dunes near Lake Michigan.

Stump: 

Okay so all plants fall into four groups. Starting with? 

Li: 

Ok, so the mosses. 

Hoogerwerf: 

Mosses are plants that do not reproduce by seeds but by spores. 

Li: 

So, they don’t have this water transporting system, and therefore they have to be in a wet area.

Stump: 

So no trees in the mosses group. 

Hoogerwerf: 

Nope, not in today’s world. Nothing with elongated, woody stems here. The earliest trees on earth were more closely related to this group, but none of them lasted. Moving on. 

Li: 

And then the second group is the ferns. 

Stump: 

The ferns get a group all to themselves? 

Hoogerwerf: 

Yep. 

Li: 

Ferns are the first group of vascular plants. So meaning that they start to have water transporting systems.

Hoogerwerf: 

But still not going to find any trees among the ferns either, because though they might have water transporting systems, none of the fern species today have woody stems.

Li: 

And then, of course, we have conifers, okay? And conifers are just one of the five major groups of gymnosperms.

Stump: 

OK, so gymnosperms is the third group of plants, and some but not all of them are trees, like the conifers? 

Hoogerwerf: 

Right. Gymnosperms as a whole is a relatively small group today, with something like 1000 species total. And the conifers are 500 or 600 of those, depending on who you ask, of course. And it includes the largest and tallest trees in the world—the redwoods—and other common trees, especially in the northern latitudes: our spruces, firs, cedars, and hemlocks. 

Stump: 

One more group?

Hoogerwerf: 

Yeah and this is where we find the rest of the trees we’re looking for. 

Li: 

And then you have angiosperms. And when you get to angiosperms, of course, you know, about 250,000 species.

Hoogerwerf: 

So while almost everything in the gymnosperms is a tree or a shrub, the angiosperms as a group includes a lot of plants that aren’t trees, including flowers, grasses, cactuses, vines…

Stump: 

And all the trees that probably a lot of us think about when we imagine the archetype of a tree. 

Hoogerwerf: 

Maples, oaks, ash, hickory, cherry, willow— 

So those are a lot of categories for you to start placing your trees into. What does that do for your blooming and buzzing confusion? 

Stump: 

I’m still at the slightly overwhelmed stage now, as I realize that a tree is not just a tree and start to get a glimpse of the individuality and all the different kinds of trees. But at least I’m getting some broad categories and conceptual handles to help order my experience. Let’s keep it going and move from these categories to functions. What does a tree do?

Hoogerwerf: 

Yeah. That’s the question that gets me excited and starts to push at my knowledge. And the answer is that a tree does a lot of things. And some of them are things we’ve known about for a long time. But there are things we’re still learning about trees that are new and surprising too. One way to start answering this question is by talking about what a tree does for people. And then all of a sudden, you can start talking in economic terms, which might be helpful, at least as a place to get started. 

Foerster: 

So on occasion, I’m asked to put a price tag on a tree.

Hoogerwerf: 

This is Vic Foerster.

Foerster: 

Really is my last name. spelled a little different, but it’s pronounced “forester.”

Hoogerwerf: 

But Vic is actually not a forester but an arborist. 

Stump: 

[laughs] That sounds like a distinction without a difference. But I suppose that’s part of the jargon that is important to tree people? 

Hoogerwerf: 

Well there is a difference. Generally, forestry looks at whole forests thinking about things like how to manage a forest for harvesting timber. An arborist looks at a specific, individual tree; sometimes you call an arborist a tree doctor. They have pretty different sets of knowledge and education. And so as an arborist, Vic is well trained to be able to tell us something about how a tree might be valued, and he actually has to do this for people. 

Foerster: 

And it could be a tree for an insurance company where the trees fell in a storm. And they need to know how their client can be reimbursed. It could be a tree trespass situation, where someone has gone on to somebody else’s property, cut their tree down, and they need to be compensated for that as well. Anyways… so we take four factors into account to try and determine that tree’s value. One, size. Two would be species––you know, white pine would be far more valuable than, say, a willow; or a red oak could be more valuable generally in a landscape setting than a box elder.

Stump: 

Wait. Why is red oak more valuable than a box elder in an urban setting? Because of the wood or something? 

Hoogerwerf: 

Well, no, because usually people aren’t going to turn an oak from their yard into lumber, unless you’re someone like me who does weird stuff like that. 

Foerster: 

Generally, either aesthetic or just functional. Shade serves a purpose or serves that purpose better than another species. So species size, health. Healthy tree is more valuable than a half-dead one, right? And then location would be the last factor. That ash tree that is so pivotal to that site, is more valuable as a landscape tree than one sitting on the edge of the woods across the pond. You could lose that tree over on the edge of the pond, and you wouldn’t even know it’s gone. You pull that ash tree out of there, and it makes a very big difference to the park. 

Stump: 

So he’s really talking about what it’s worth for someone to have a tree in their yard or their park, and the idea is that different trees would be valued differently by people depending on where they are and what they look like. That’s all fair. We like shade; we like greenery. And there’s even some studies that show that people’s health is improved when they spend time in forests and near trees. But that all seems pretty subjective. 

Hoogerwerf: 

There’s another level to this that might even be more utilitarian and related to this idea of valuing a tree. There are some online tools I have been playing with where you can plug in some data about a specific tree, and it will spit out an economic value based on the services the tree provides and what it will provide in the future. 

Stump:

Interesting. So what are some of those things?

Hoogerwerf: 

So I plugged three of the trees in my yard into an online calculator called MyTree. (We’ll link to that in the shownotes.) So I added the sycamore that I already mentioned out front, and also a magnolia and ornamental cherry tree. And it spits out what looks like a nutritional label on a food package, with dollar amounts. It turns out these three trees in my yard over the next 20 years will provide about $300 dollars worth of storm water mitigation, $500 of energy savings—probably from the shade it provides to our house—$250 in air pollution removal, $240 in carbon dioxide uptake, and $140 in avoided energy emissions. Altogether that’s $1500 over the next 20 years. So it’s not replacing my lottery winnings or anything, but you can imagine that would go up pretty quick if I plugged in all the trees on my block, for instance. 

Stump: 

Ok, so beyond simply liking a tree for aesthetic reasons, we’re starting to build a bigger portfolio of services here. Trees pull pollution out of the air, help with our energy use, help with stormwater runoff, and pull carbon dioxide out of the air. 

Hoogerwerf: 

And that last one is pretty important in a world where atmospheric carbon dioxide is a main driver of global climate change. So let’s switch away from individual trees and back to forests. And this is something Jianhua Li is thinking a lot about. 

Li: 

If you think about that…we need to think about the climatic change and that we want to reduce the amount of CO2 in the air––which is the main reason, one of the main reasons for the rise of temperature––then you’ve got to do a few things. One is you just, you know, don’t use much fossil fuel, and so you don’t release much CO2. And then the other one is to increase the carbon sequestration by biological entities, and you know, mostly trees, right? Because we know trees and shrubs, and both of them are woody plants, they have a higher capacity of sequestering CO2.

Hoogerwerf: 

So the easy answer is to plant more trees. But we’ve already learned that a tree is not just a tree. 

Li: 

Now, when you compare, you know, beech trees and hemlock trees and then Hemlock trees, they sequester more carbon into their body, and, you know, forming lignins. And lignins are such a big molecule, they won’t be able to decompose that easily.

Hoogerwerf: 

So not only do some tree sequester carbon more quickly, but also hold on to that carbon for longer. And so this kind of knowledge is going to be helpful as we start to think about how to manage our forests over the next decades as the climate warms.

So there’s one more place I want to go with your question about what trees do. We’ve known for a long time about some of these services that trees offer to people. People have been using trees as a resource for millenia. Science has definitely helped us to understand that value better, especially in the context of climate change. That might change some forestry practices or planting practices, but I don’t think it’s going to change many people’s idea of what a tree really is. 

Stump: 

Now we’re talking ontology again. Do you have something that will change people’s idea of what a tree really is?

Hoogerwerf: 

Well, maybe. At least, there’s a growing body of scientific evidence that starts to show that trees have a lot more complex interior lives than we usually give credit for. 

Stump: 

Uh…the interior lives of trees?

Hoogerwerf: 

I think so. 

Li: 

In recent years, people start to realize, “Well, trees are not really just, you know, for example, in this woods, they’re not really just standing there, not doing much and just trying to compete.”

Hoogerwerf:

There’ve been several popular books in the last 10 years or so that have really captured the public imagination. Peter Wohlleben wrote The Hidden Life of Trees in 2015, which became a bestseller; and Susan Simard wrote Finding the Mother Tree in 2021. 

Stump: 

Don’t forget the popular Pulitzer prize winning novel The Overstory.

Hoogerwerf: 

Yeah, and all of those books, at least in part, deal with how trees communicate with each other. 

Foerster: 

The thinking forever is that trees don’t communicate underground unless—communicate is a risky word to use here. But if you bear with me for a moment, yeah. Like, for instance, red oaks: the roots will graft to one another underground, and they’ll share sap with one another. So in that sense, they’re literally moving fluid amongst each other. And that’s been known for a long time; it’s part of the problem why oak wilt and Dutch elm disease moves so quickly. The fungal organism will be transported underground via root grafts.

Stump: 

Vic makes the point here that communicate is probably a tricky word. Lots of things communicate; I’d say all living things communicate in some way, and even non-living things like computers communicate with each other. But that’s different than language—at least the kind of language humans use. So before I really change my ontology of trees and give them sentience, I’m going to need more details about what’s going on here. What do we know from the science? 

Hoogerwerf: 

Well, that’s a really good question. And for some reason these recent books got picked up by science communicators and others, and this story was told that forests are really just big super organisms that are sharing resources, and even that trees are altruistic and intelligent. But a lot of this science is pretty new, and a lot of it has not really been replicated widely, so it’s not widely accepted by a community of scientists who are studying trees and ecosystems. So to help answer this question, I’m bringing in one of our more frequent podcast guests. 

Lindroth: 

Yeah I could riff on trees for hours. I absolutely love trees.

Hoogerwerf: 

This is Rick Lindroth.

Lindroth: 

I’m a recently retired professor of ecology from the University of Wisconsin-Madison.

Hoogerwerf: 

And so I asked him what’s actually going on. 

Lindroth: 

There’s been a lot of interest in tree communication scientifically for a number of decades. And that communication is not done by talking, although we like to refer to talking trees; but their mode of communicating is via chemical signals, not sound waves.

Hoogerwerf: 

Rick did point out that some recent research might actually show that plants can respond to vibrations, but mostly the way trees communicate is through chemicals. 

Lindroth: 

So we well know now that when some plants are damaged by an herbivore––let’s say, think of a caterpillar sitting on a leaf munching away––the plant releases volatile organic carbons––VOCs, or sometimes people call them green leaf volatiles––into the air that attract natural enemies like predators and parasites of that insect that then come in and attack the insect. And so the plants are recruiting the enemy of their enemy.

Hoogerwerf: 

So that in itself is fascinating and reminds me of the liveliness of trees. But they don’t only send chemicals through the air. Vic mentioned the kind of underground connections that trees have, and it goes a long way beyond root grafts.

Lindroth: 

Historically people, even scientists, have thought of plants including trees as independent being: don’t move and have roots stuck in the ground and the purpose of those roots is to anchor that organism, as well as to absorb water and nutrients. But now we know that the soil is a vastly rich, biologically diverse community––ecosystem––and that trees don’t just suck up nutrients independently of those other organisms. Their roots are intimately associated. I think some like roughly 95% of all plant species are associated with these fungi that are called mycorrhizal.

Hoogerwerf: 

And what Susanne Simard in her book Finding the Mother Tree was seeing, is that at least in the trees in the systems she was studying, trees were sharing resources not only with kin and not only trees of their own species but trees of other species. There have been other studies that show that when a tree dies, it will send resources to other trees nearby. 

Stump: 

These are interesting results, to be sure, but I’m a little skeptical about how much we can really conclude from these particular studies.

Hoogerwerf: 

Rick would agree with your skepticism. Susanne has definitely opened the door into some really interesting questions, but there is a lot of work to do yet. 

Lindroth: 

Scientifically, there are hints that some of those components are true, but the stories and the impressions have gone way beyond what the sciences can support. 

Hoogerwerf: 

So last summer, we were down in North Carolina and took a walk with Dan Richter

Richter: 

Professor of soils at Duke University.

Hoogerwerf: 

Dan was a professor of mine in graduate school; and as a soil scientist, trees are a big part of what he studies. And you asked him this question about ontology. 

Stump: 

I think I was specifically referencing aspen trees because we saw these on another walk through woods several years ago in Colorado. 

Richter: 

Those aspen clones are just incredible. You know, it’s one species. And, you know, the rooting system is basically easily seen to be one organism––lots of trees, lots of area, acres and acres sometimes.

Hoogerwerf: 

These aspen clones, which look like different trees above ground are actually genetically identical to each other, all sharing a single root system underground. That’s why we can talk about a grove of aspens as a single individual. Most trees don’t grow in clonal colonies like aspens but you start to wonder when one tree ends and the other begins.  

Stump: 

So my question for Dan was, “What are the characteristics that we need to be able to say that this thing is a tree?”

Hoogerwerf: 

And all the talk about tree communication and sharing of resources makes you start to wonder if we’ve got the boundaries right. 

Stump: 

But Dan had some helpful limitations here. 

Richter: 

But here you’ve got trees that have evolved very different periods of time, conifers and hardwoods, and some of them associated with fungi that are completely different families from others. The way I interpret the communications and the intermingling of fungi below ground is that yeah, that occurs, but it’s not like an aspen clone. And that’s partly justified in my mind with experimentation, where you can label the CO2 and watch it be photosynthesized by one plant and maybe pass it to another of the same species in the greenhouse or in the field. But I don’t think it’s a mass transfer of shared resources. There’s some of that, and it’s beautiful. I mean, they are connected. Stumps: you can go to a pine forest, old field pine forests, cut all of the pines down except a few of the overstory trees; and those few overstory trees will keep the stumps alive. Amazing. [Jim Stump laughs] But they’re the same species, and it’s kind of keeping the cells of the other root systems that are now a stump alive. And they kind of just…It’s amazing, but I don’t know if it goes beyond that.

Stump: 

For the record, I’m all for keeping the stumps alive! So what’s the takeaway here? 

Hoogerwerf: 

Well, I think I’m convinced by the science that trees are doing some more interesting things than we have typically considered. And I think Rick said it better than me. 

Lindroth: 

I will say this: trees are way more responsive, way more sensitive to their environment, way more responsive to their environment––and in fact, turn around and affect their environment––way more than science and humanity has ever given them credit for. They are very dynamic; and they’re constantly testing, receiving input from their environment and releasing things into their environment to change and alter their environment. So they’re not just like you know pieces of wood stuck in the ground––not whatsoever.

Hoogerwerf: 

Does this do anything for your ontology?

Stump: 

It’s interesting, to be sure. I love learning about the details of how things work, and this certainly enlarges my understanding and appreciation of how trees have adapted and evolved to survive and thrive in their ecosystems. But being dynamic, receiving input from their environment, and responding to that…I’m afraid that just sounds like the basic characteristics of life. I can imagine (which, I guess, is what philosophers do instead of actually empirically testing things) that trees that release chemical signals to attract a predator of the thing eating their leaves is going to be more a successful tree in the long run; but that doesn’t persuade me that trees have intentions or are altruistic or  intelligent. If we say trees have complex inner lives or are intelligent, that doesn’t raise my estimation of trees so much as lower my estimation of what we mean by intelligence!

Hoogerwerf: 

That’s a little harsh! There are some people who are trying to include trees in the definition we have of intelligence. I don’t think I’m ready to do that. But the way I was trained to think about trees, even as someone who loved trees and learned the names of them, is that they barely were alive and definitely weren’t a dynamic part of the environment they were in. When I read and talk to people like Rick about what trees do, I’m always just blown away by how much I have underappreciated them.

Stump: 

I get that there has historically been a tendency for us to devalue other parts of creation, and it’s a very helpful corrective for us to see the amazing and really cool abilities of trees. And as with anything that’s alive, I’m even fine recognizing that there is some degree of agency in trees. So yes, we shouldn’t think of them as just a stick in the ground. But as my general tendency is in these conversations, I can’t bring myself to say that trees are people too! Just sticking with communication, I don’t see how what trees do is remotely in the same category as human language, which allows us to see trees as something. I don’t think humans are symbolic for trees in the way that trees are symbolic for us.

Hoogerwerf: 

Well, let’s talk about trees as symbols.

[musical interlude]

Hoogerwerf: 

Several times already, we’ve implied that most people have this notion of trees that they are just inert pieces of the scenery. And if that’s true in recent history, it has not always been true, not in the same way. The ancient Israelites and the culture of that time seemed to give trees a lot more agency than that. 

Stump: 

You mean like “the trees of the field clapping their hands”?

Hoogerwerf: 

Yeah, as someone who has loved trees for a long time, that verse from Isaiah 55 has always been one of my favorite verses. But there are a lot of places where trees play an important role in the Bible and act as a symbol. And I think it might be interesting now after learning about what trees are, where they come from, and what they do, to look at some of the symbolism of trees in the Bible. 

Stump: 

Sounds like we need a Bible scholar. 

Hoogerwerf: 

How about two? 

Boogaart: 

Yeah, Tom Boogaart and taught for 32 and a half years at Western Theological Seminary.

Davis: 

I’m Ellen F. Davis. I’m the Amos Regan Kearns Distinguished Professor of Bible and Practical Theology at Duke Divinity School.

Hoogerwerf: 

I went for a walk with Tom Boogaart in Holland, Michigan; and Kent Frens also came with us––a previous podcast guest and a friend and pastor here in Grand Rapids, Michigan. Kent probably deserves some credit actually for this episode since one of the first times I heard him preach was when he did a sermon series on trees. 

Stump: 

And you and I sat down with Ellen Davis in her office at Duke Seminary, which wasn’t in the woods, but Dr. Davis is a renowned Old Testament scholar and particularly looks at the Old Testament through an agrarian lens, which of course will give some priority to trees and other plants. 

Hoogerwerf: 

Let’s start with Tom.

Boogaart: 

Yeah there’s a couple things, if we’re going to talk about trees, we got to step back a little bit and say a few things before you know what’s the Israelite worldview in which trees emerged as significant.

Hoogerwerf: 

One of the things that Tom pointed out was that the people in ancient Israel had a very different idea of the connection between the spiritual and the physical world. 

Boogaart: 

So if you indwell the biblical world, one of the things that you sense immediately is that the line between the spiritual and material world is very thin. And in modern culture, it’s almost absolute. So most people––and most Christians, I’d say, and not just including scholars––really have an assumed worldview in which the spiritual world is distinct from the material world. 

Stump: 

Today you hear people talk about “thin spaces” at certain places that seem to point us more particularly to the divine. This was taken from ancient Celtic spiritual practices, but is probably much more common among ancient religions of all kinds.

Boogaart: 

The people of Israel thought that the particular structures of the created order would suggest to you how the world was structured. And so they saw a kind of correspondence between the life of nature and the human life, for instance. And so the tree then becomes a symbol. And so they start thinking, “Well, wait a minute. You know, God’s a gardener”; that’s a big image in Scripture. God’s a gardener. God plants trees, you know, not just the Garden of Eden, that thing gets writ large. Every nation is a planting of God; the whole world is the Garden of Eden. God is the gardener. Jesus says, “I’m the vine, and my Father is the gardener.” And then Jesus says, “I’m the vine; you are the branches.” “You are branches in my tree,” let’s say. And so the human community is seen as a tree. Jesus is seen as a tree. God is seen as a gardener. And then they’re off and running. 

Hoogerwerf: 

So now with our best attempt at viewing the world through the context of these ancient people we asked Tom and Ellen to talk about one example of a place where trees play an important role in scripture. Here’s Tom with an example from the New Testament.

Boogaart:

So Jesus picks up the theme and says, you know, in Matthew 13, “The kingdom of heaven is as a grain of mustard seed, though it is small, smallest of all seeds, though it is small, it grows and becomes a great tree.” And then it says, “and the birds of the heavens nest in its branches.” Well, what he’s offering is kind of a mission statement for the church. But if you think about it, the work of God begins small; there’s a seed. And then it grows and expands if it’s a lifegiving system. And then as the tree expands, it creates space. And in that space, the rest of creation can find room to move. And not only that, it bears fruit; it also the fruit that’s there. So the space that’s created, you get the theme of the shade. You can “live in its shade”––one of the images in the Old Testament is, you know, you can sit in the shade of the vine and under the fig tree, type of thing. 

Stump: 

The Kingdom of God is like a tree. How does our new found scientific understanding of what trees are contribute to understanding this metaphor or symbol any better?

Hoogerwerf: 

Well, if we’re previously thinking of trees as these inert sticks in the ground, and now we’re thinking of them as alive and dynamic and responsive, that should probably make us think of the Kingdom of God that way too. Like a tree, the Kingdom of God is deeply intertwined with the world around it. And the structure of a tree is itself something that grows from this tiny thing; and so too the Kingdom of God is not just poofed into existence in all its maturity, but is also a growing and dynamic thing that perhaps starts as something almost invisible. 

Stump: 

It makes me think of the way Dallas Willard described the Kingdom of God as this sphere of activity and influence that goes the way the King wants it to go. And that begins in our own tiny spheres of influence but should grow and expand. And there is also the interconnectedness and responsiveness of trees that we’ve come to understand. That should also point us to something more complex about the Kingdom of God.

Hoogerwerf: 

Let’s hear the next example. Ellen Davis started in a place you might not expect. This is from Deuteronomy 20.

Davis: 

“When in your war against a city, you have to besiege it for a long time in order to capture it, you must not destroy its trees, wielding the ax against them. You may eat of them, but you must not cut them down. Are the trees of the field human to withdraw before you enter the besieged city? Only trees that you know do not yield food may be destroyed.” This passage, which we kind of tend to look right past, this is a really central passage for the core environmental principle of Judaism, which is about Bal tashchit. It’s the Aramaic rendering of this “do not destroy.” Okay, and so it then becomes through centuries up until the present a whole series of teaching on this principle extending it. 

Stump: 

From this come all kinds of rules about breaking vessels and wasting food or burying people in expensive garments. 

Hoogerwerf: 

But all of this comes out of a verse of not destroying trees. Dr Davis cited one of her doctoral students, Mari Joerstad, who wrote a book called The Hebrew Bible and Environmental Ethics. 

Davis: 

And she makes a really good argument that––and I’m convinced she’s right––that what she calls personalistic but non-human nature in the Bible exercises that non-human, non-animal creatures in the Bible are nonetheless what we would consider to be persons. You know, they have voice; they have agency; they give praise. The land vomits out Israel. The things that we associate with personhood ascribed to non-animal, non-human nature, including trees. And she said, it’s not just metaphor; it’s a different perception of capacity. And I think she’s absolutely right. And all of that, I think, underlies this notion of “do not destroy.”

Stump: 

Hmm…trees are people too? I’m going to have to think about that some more. 

Hoogerwerf: 

How about my favorite verse in Isaiah about trees clapping their hands? Isaiah 55, verse 12: “You will go out in joy and be led forth in peace. The mountains and hills will burst into song before you, and all the trees of the field will clap their hands.”

Stump: 

Isn’t that just a metaphor?

Hoogerwerf: 

I’m not as sure about mountains singing songs, though there is a particular sound to being in the mountains for sure. But trees clapping their hands always seemed like maybe it was more than a metaphor. If a tree’s hands are its leaves, then they do clap. The quaking aspen even has flattened leaf stems that make the leaves “quake” in the wind. But I think this verse and others are more than just a fancier way of saying that trees make sound when the wind blows. It’s kind of like how you and I went and tried to worship alongside the ocean back in episode 143 and even listen to the ocean and learn how the ocean praises God.

Stump: 

Yes…I was really impressed with that experience at the ocean, not just thinking it was this inert thing that could only prompt a sense of wonder and worship in us, but that it itself was also worshiping in its own way. Maybe I need to open myself up a bit more here to the “non-human personhood” of trees, as Davis called it. Maybe these are more than metaphors but point to some deeper ontology that we should recognize in trees and other created things. The trees are not simply being blown; they are actually praising God.

Hoogerwerf: 

And they praise God in their own way. 

Lindroth: 

I think things doing what they were intended to do brings God pleasure and brings God a sense of joy and maybe even a sense of wonder himself, you know? And so yes, plants, including trees, doing what trees do…I think that’s giving praise to God. 

Hoogerwerf:

So a verse like this can be a metaphor. The trees clapping their hands as a metaphor for all of creation rejoicing, but it’s also literal. The trees are rejoicing by being trees.

Davis: 

And seeing how creatures express their being in response to the one who gave them being. That’s not metaphor. It’s not verbal. And you may not have to have a brain to do it, but that doesn’t make it metaphor.

[musical interlude]

Hoogerwerf: 

Well, our walk through the woods here is coming to an end. Has this changed anything for you? You hinted at some softening earlier to the whole “trees as persons” thing.

Stump: 

I’m not thrilled about using “personhood” or “intelligence” to refer to trees. But maybe there are a couple of things I think I might defend now that I wasn’t quite articulating at the beginning of the episode: Trees were praising God for a long time before any humans were around. In fact, it seems pretty likely that God takes a lot of delight in this kind of thing. For a couple hundred million years, the trees just did their thing. 

Hoogerwerf: 

And when humans came along, they may even have started to hinder the ability for trees and other creatures to praise God well. This brings up another tricky question for me. I like to work with wood. I’m sitting at my desk right now, made out of a honey locust tree that used to shade my backyard. It’s not praising God anymore with its leaves or bark or roots or chemical signals being sent through the air and soil. But just like the fact that we can be thankful for the food we eat and understand it as a gift given, maybe the desk is a testament to the praise the tree once gave. I can see in all its grain the many years it put on growth and even the places where branches probably began growing. 

Stump: 

So that’s really interesting and, of course, brings up the tricky relationship we have with the rest of creation. And all living things transform the earth’s resources into other things, and the best I can say now is that we ought to be thoughtful and careful about how we do that. My intuition is that it wouldn’t be good for all trees to be turned into desks, I suppose.

Hoogerwerf: 

I don’t know that we need that many desks. Probably some trees need to die and rot to create new soil for future forests too. You said you would defend a couple things. One is that trees praise God and have for a long time. What’s the other? 

Stump: 

Well I guess that there are a lot of things we don’t know yet about the capacities of trees. The science and biblical symbolism has made me more curious, and it has at least disrupted some of my categories. Maybe I’ve been too quick to limit what kind of things trees are. 

Hoogerwerf: 

I think science has a lot of really interesting things still to tell us about trees and plants and probably all other creatures. My hope is that anytime we learn something new, it helps to remind us about how alive trees are, and that each reminder about their aliveness will enrich our view of God’s creation. 

Stump: 

And let’s not limit ourselves to theoretical or abstract knowledge of them. One of the things that impressed me most about creating this episode was how much our guests just loved being in the trees. It makes me want to spend more time among the trees, getting to know them even more, and even learning from them? That might be one more thing I’ve come to accept about the kind of thing trees are: they can teach us.

Hoogerwerf: 

That reminds me of a poem by Mary Oliver called “When I Am Among the Trees.” Let’s let her poem have the last word. 

When I am among the trees,
especially the willows and the honey locust,
equally the beech, the oaks and the pines,
they give off such hints of gladness.
I would almost say that they save me, and daily.

I am so distant from the hope of myself,
in which I have goodness, and discernment,
and never hurry through the world
but walk slowly, and bow often.

Around me the trees stir in their leaves
and call out, “Stay awhile.”
The light flows from their branches.

And they call again, “It’s simple,” they say,
“and you too have come
into the world to do this, to go easy, to be filled
with light, and to shine.”

Stump: 

Amen.

Hoogerwerf: 

Thanks to everyone who went out into the woods with us or otherwise took the time to talk about trees. Dan, Rick, Ellen, Tom, Kent, Vic.

Stump: 

And thanks to the trees themselves.

Hoogerwerf:

Language of God is produced by BioLogos. It has been funded in part by the Fetzer Institute, the John Templeton Foundation, and by individual donors like you, who contribute to BioLogos. Language of God is produced and mixed by Colin Hoogerwerf. That’s me. Nate Mulder is our assistant producer. Our theme song is by Breakmaster Cylinder. 

BioLogos offices are located in Grand Rapids, Michigan in the Grand River watershed. If you have questions or want to join in a conversation about this episode find a link in the show notes for the BioLogos forum or visit our website, biologos.org, where you will find articles, videos and other resources on faith and science. Thanks for listening.