Saturday, January 26, 2019

The Hidden Life of Trees -- A Review

A surprise bestseller this past year in the U.S. was "The Hidden Life of Trees," a book that gained popularity in Germany before being translated into english. In a progression of 36 short chapters, the author, forester Peter Wohlleben, draws big conclusions from his experience in a forest he cares for in Germany. Using heavy doses of anthropocentric language, he portrays trees as feeling, communicating and interrelating in surprisingly human ways. It's an appealing notion, and he claims to back it up with a list of sources in the back of the book.

As a naturalist trained in botany and water quality, with decades of involvement in nature preserve management and other environmental issues, I've read and reviewed a number of books that claim to give you the inside scoop on what nature is really like, and have noticed some similar themes. A book will garner more interest if it has an applecart to spill and an "Other" to dislike. In this case, the applecart is antiquated views of trees, and the "Others" to look down upon are narrow-minded scientists and commercial foresters. Another common ingredient is to let the reader off the hook by suggesting we as individuals need expend no energy to compensate for all the ways human activity has thrown nature out of balance.

Nearly all of these books are written by non-scientists and reviewed by non-scientists, leaving the public unprotected from any misinformation the books may carry. Though I share the author's sense of appreciation and wonder for all that trees do, the Hidden Life of Trees comes across as a mixed bag of laudable sentiments and cringeworthy anthropomorphism, truth and appealing fiction, nice descriptions and gross generalization. Readers will come away informed and misinformed. Two German scientists who started a petition objecting to the book's claims characterized it as a "conglomerate of half-truths, biased judgments, and wishful thinking derived from very selective and unrepresentative sources of information.”

Where, one wonders with books like this, are those who might check a manuscript for accuracy? Reviews in the mainstream news media, however, tended to minimize the book's problematic aspects. Perhaps impressed by the book's popularity, believing the book's overall message to be medicinal in our age, they cast the scientists who found flaws as mere flies in the ointment.

Wohlleben's advocacy for old growth forest taps into our wish for some oasis of stability and peace in a radically changing world. There's an appealing call to let trees grow slower and live longer. His dream is "ancient forests free from any human interference." But if you read the book, note how little he demands of us in terms of intentional effort to restore nature. The index doesn't even include a reference to restoration. It seems it happens on its own, over hundreds of years, and that "no real sacrifices need to be made." For example, conspicuously missing from several references to fire-dependent forests in the U.S. is any mention of the need to conduct prescribed burns in order to maintain them. He squashes a few exotic insects he accidentally brought home after a trip, knowing that introduced species can do harm, but doesn't grapple with the larger issue of how to reduce the import of potentially invasive species, or how to reduce the harm done by those already established.

A deep love of trees needs to be mixed with an understanding that, for many smaller species that cannot tolerate shade, trees are the enemy. Though the author acknowledges this, that in "deep shade, wildflowers and shrubs don't have a chance..., " and that pollinating insects find little food in forests dominated by species with wind-pollinated flowers, he often speaks of deep, unbroken forest as the all and end all. Any discussion of biodiversity must mention not only forest, but grasslands, savannas, and shrub habitat as well. Though it's important to save old growth forest, preserved open space in central New Jersey and elsewhere in the east is too uniformly dominated by trees to the exclusion of other needed habitats.

Below are some examples of the mix of information and misinformation to be found in the book.

Chapter 1 Friendships
Here, Wohlleben makes broad pronouncements about forests. Since trees in a forest benefit from the "consistent local climate" they create, they have reason to work together, even to the point of nourishing their competitors through interconnected roots. He describes forests as "superorganisms with interconnections much like ant colonies." Being someone who believes in the importance of cooperation and collective action generally, I certainly sympathize with such a portrayal of the forest. But the author offers as evidence a very misleading story about encountering an old stump in the forest being kept alive by the trees around it. Are the younger trees showing reverence for their elders? Remarkable, you might think, unless you happen to know that the stump and trees he is talking about are beeches. Since beeches create clones, the older and younger trees he describes are not separate trees, not "friends" as he later calls them. They are in fact one tree with many trunks, connected underground by a root system that sends up new stems as it spreads. That he doesn't point this out is a considerable sin of omission.

Wohlleben then overreaches by declaring, "Every tree, therefore, is valuable to the community and worth keeping around for as long as possible." There may be some forest somewhere on earth where this is true, but none that I know. Certainly not in the fire-dependent pine forests of the southeast where pines would be rapidly shaded out if hardwood trees weren't kept at bay by periodic fire, or the Ponderosa pine forests of the northwest, which require adequate spacing between trees to reduce the risk of wildfire leaping up into the crowns. Certainly not in the many second growth hardwood forests of central New Jersey that are clogged with stunted trees. The author believes openings in the canopy to be the enemy. The sunlight, he says, will heat the soil and cause loss of humus. Wind will get in and blow down the surrounding trees. There may be some truth to the increased vulnerability to wind, but if sunlight never reaches the ground of our forests, only the tree species that can survive in shade will regenerate. There are many kinds of forests, some of which thrive on periodic disturbances like fire. Though he gives a useful description of such forests on page 208, he often presents his forest of oak and beech as somehow universal.

Chapter 4 Love
One thing that baffles people wanting to know nature better is its mind-boggling diversity. They've heard that diversity is a good thing, but the long learning curve can be intimidating. Wohlleben gets around this by making broad pronouncements based on the apparently paltry number of tree species in his forest. He seems to have only two main types of deciduous trees--oaks and beech--but then often writes of them as if they are representative of all the deciduous trees in the world. With this approach, and by speaking of trees as if they were like people who "plan" and "agree" and "go for it," he can simplify nature, make it seem easily knowable, familiar.

Sometimes he begins a paragraph with a misleading statement, like "When beeches and oaks put blooming on hold for a number of years, this has grave consequences for insects as well--especially for bees." Now, anyone familiar with tree pollination will know that beeches and oaks are wind pollinated, and are therefore not much used by bees. He eventually explains this, but not until after he's had the reader imagining starving bees dropping out of the air for lack of pollen.

It's also a bit comic to note that he describes girdling trees in the previous chapter as "brutal," then in the Love chapter describes beeches and oaks as colluding to starve pregnant boar and deer in order to limit their numbers. That's some tough love.

One tidbit I was glad the author included was the tendency of genetically isolated populations to die out over time. "Completely isolated stands of rare species of trees, where only a few trees grow, can lose their genetic diversity. When they do, they weaken and, after a few centuries, they disappear altogether." Some of my more satisfying work involves taking seed from isolated populations of a species and planting them in other conducive locations around town, essentially creating a pollen corridor of sorts, bridging the gap between otherwise isolated populations.

Chapter 16, Carbon Dioxide Vacuums
Here, Wohlleben attempts to debunk the notion that the carbon that trees absorb while living is simply rereleased to the atmosphere after death. It can be discouraging to realize that trees are not some magic fix for climate change. Figuring out how best to sequester carbon in plants and the soil is a vital subject, given its potential to lessen the damage we're doing to the climate, but unfortunately this chapter offers up appealing fictions. For one, he claims that most of the CO2 absorbed by a tree "remains locked up in the ecosystem forever." A dead tree trunk, he writes, is "gnawed and munched" and "worked, by fractions of inches, more deeply into the soil."
"The farther underground, the cooler it is. And as the temperature falls, life slows down, until it comes almost to a standstill. And so it is that carbon dioxide finds its final resting place in the form of humus, which continues to become more concentrated as it ages. In the far distant future, it might even become bituminous or anthracite coal." 
It's a lovely image, and largely fictional. For one, half of the atmospheric carbon fixed by a tree is rereleased as part of the living tree's ongoing respiration. The author acknowledges the tree's need to respire later in the book, in Chapter 33, Healthy Forest Air, where he directly contradicts his earlier description.
"It's not only the trees that are exhaling large amounts of carbon dioxide in the dark. In leaves, in dead wood, and in other rotting plant material, microscopic creatures, fungi, and bacteria are busy in a round-the clock feeding frenzy, digesting everything edible and then excreting it as humus."
That "feeding frenzy" means those organisms are respiring, turning lots of the dead wood's carbon back into CO2. There's also sloppy use of terms. Carbon dioxide doesn't "find its final resting place" or "sink into the muck," because carbon dioxide is a gas. Rather than getting cooler and cooler as one goes down, the deeper soil layers are a fairly uniform 55 degrees, plenty warm for biological activity.

He actually blames commercial logging for preventing coal from being formed, after having explained that the coal we now use was formed under primeval conditions completely different from the upland forests where most trees are harvested, and over a time span that is useless for our predicament. I'd be glad to blame commercial logging for all sorts of things, but preventing coal creation is not one of them.

Another deception quickly follows when the author claims that old trees grow faster than young ones. Ongoing growth among the well-aged is an appealing concept, whether for people or trees. He's got our sympathies as he sets out to upset the applecart of "scientific assumptions," by saying that "Trees with trunks 3 feet in diameter generated three times as much biomass as trees that were only half as wide." But a tree with a trunk twice as thick is not twice as large. It's more like four times as large, given that a trunk twice as thick has four times the area in cross section. It's the younger tree, then, that grows faster for any given amount of space taken up in the forest.

Chapter 30 Tough Customers
This chapter asks a useful question: How do long-lived trees in a forest adapt to rapidly changing climate? His answer is that genetic diversity within a species will allow the trees in his forest to survive even sudden changes in climate. He points to a sudden, dramatic cooling that occurred 14,000 years ago, and to the long north-south range of beeches, extending from the Mediterranean to Sweden. At least concerning the latter, I find some common ground with the author, having myself pointed out the long north-south ranges of species in the eastern U.S. when people claim we need to move southern plant species northward in order to adapt to a rapidly warming planet.

Chapter 32 Immigrants
Anthropomorphism, that is, attributing human characteristics to non-human things, can be charming and comforting. It can help us empathize with other living things. But when it comes to invasive species, that tendency to anthropomorphize has gotten a lot of authors into trouble. Introduced species are not like immigrants. Human immigrants are of the same species as the other humans they join. Introduced species are, by contrast, more analogous to martians--a different species that if they showed up might just mingle among us and look cute, or they might start taking over our homes, in which case we'd think them less cute.

Giving this chapter on introduced species the title of "Immigrants" therefore misleads readers from the get-go. The author then proceeds with some of the stock arguments used by invasive species deniers, whom I know well from having reviewed multiple books, opeds, and articles in the genre. There's the claim that "nature is constantly changing," and the pessimistic view of "attempts to conserve particular landscapes." And there's the seeming reassurance that "most introduced species pose no threat to native trees." He claims, falsely, that the human spread of species is not much different in degree from what has occurred naturally, and that "there is always a sufficient number of individuals that can rise to a new challenge."

But along with these familiar denialist tropes are descriptions of the problems that introduced species have caused. The solution he offers for some invading plant species--plant more trees to shade them out--is less than convincing, but at least he doesn't deny the distinction between introduced and native species, and the potential for introduced species to cause major problems.


The NY Times noted the author's "humble narrative style and the book’s ability to awaken in readers an intense, childlike curiosity about the workings of the world." The author indeed has a gift, but that gift is misused, compromising truth in favor of eliciting the desired response from his readers.

He claims to be on the forefront, pushing against entrenched views of nature, as in this call for plant rights on p. 244:
"Although this point of view has elicited a lot of head shaking in the international community, I, for one, welcome breaking down the moral barriers between animals and plants. When the capabilities of vegetative beings become known, and their emotional lives and needs are recognized, then the way we treat plants will gradually change, as well. Forests are not first and foremost lumber factories and warehouses for raw material, and only secondarily complex habitats for thousands of species."
I have seen, though, how this activism for the rights of individual animals and plants can lead to a dismissive attitude towards the larger ecological workings of nature. Though seemingly progressive in his thinking, Wohlleben also steers us backwards, towards a passive, hand's off relationship to nature--witnesses rather than informed participants.

Skepticism and Self: Science's Role in Sustaining Democracry

This is a repost from another blog of mine.
"It's a readiness to be wrong that motivates the study needed to be right."
- Yures Trooley

Andrew Zwicker, one of Princeton's two representatives in the state house, spoke this week to a full room at Mercer County Community College. It was part of a monthly series of talks hosted by the NJ Sierra Club. Assemblyman Zwicker is one of our few, perhaps the only, representative in government who is trained as a scientist. I attended not only because Zwicker is a gifted speaker, but also because of the subject.

The title of the talk, "Scientific Literacy and Democracy," struck a chord with me particularly because the plight of nature has increasingly found a parallel in growing threats to democracy. Both are at risk in a time when truth is being attacked, denied, ignored, downgraded, and generally dismissed. There is the national reality of a leader who cannot see beyond his own skin, and a broad-based, corrosive and paralyzing polarization that thrives on a dismissive attitude towards evidence.

Andrew Zwicker is a rare breed, a scientist who is also comfortable in front of an audience, and he has taken that extra step of bringing his scientific abilities into the political realm. An evidence-based perspective could be a unifying influence if it caught on among his colleagues at the statehouse.

Having a couple science degrees, I have found myself increasingly aware that my mind works differently from many who lack science training. Most significantly, that training can help direct skepticism not only outward but inward as well, at one's own views.

Most of the world's polarization and radicalism would disappear if people directed as much skepticism inward as outward. Science, and its pursuit of truth, is like a lifeline being extended to a world fractured by unfounded opinion. The political polarization we suffer through is artificially created by people who refuse to adjust their views in the face of evidence.

My views are built on varying degrees of knowledge, experience, and observation. Some of those views are better supported than others, and all are subject to revision in the face of new evidence. Scientific training is liberating, in that it allows facts to exist independent of what we might wish were true. Unentangled from our emotions and sense of self, facts need not be feared or clung to, but can be built into an evidence-based view of the world.

My older daughter went through a phase in which she'd periodically declare, with a mixture of surprise and pride, "I changed my mind!" There's pleasure in that flexibility, that openness to new evidence, and my sense is that many people have lost that openness. Recently I was on an advisory committee, developing a list of proposals for action on climate change. The subject had everything to do with science, but only a few of us appointed to the committee had scientific training. A couple of us with a scientific background made suggestions, with some supporting evidence, expecting that if others disagreed, they would provide counter evidence. Being open to new evidence, I might have changed my mind if someone had a more convincing argument. Instead, people simply didn't respond, and continued to stick to their own views without feeling compelled to defend them. They'd mention something they'd read in a book that they liked the sound of, and it would turn out that even the book, though about science, was written by someone who lacked training in science.

During Q and A with Assemblyman Zwicker, I mentioned this curious phenomenon, that science-related advisory committees and science writing can be dominated by people lacking science training. A science editor for the NY Times once wrote a deeply flawed oped denying the threat of invasive species. Turned out he was a Princeton grad with a PhD in english. There are no doubt science writers who know much more than I do about many aspects of science, and yet there's something about science training that cultivates a healthy two-way skepticism, inward as well as outward. It's a readiness to be wrong that motivates the study needed to be right.

After the Q and A, a woman came up to me and said that data is the issue. Most people don't know what to do with data. Maybe she was referring to an analytical ability that develops over time. Science presents you with data, and you have to figure out what the data is suggesting, if anything, and whether it's strong enough to be conclusive. The process requires a great deal of patience, but it also requires an acceptance that there is a reality outside of oneself that really doesn't care about us and our emotional needs at all.

It's possible to experience that reality out in nature, when one gets far from the ever-expanding footprint of lights and noise, far enough that the only human presence is within one's own skin. For me, it's happened a few times, most strikingly while on an ocean shore late at night. The ocean waves crashed against the sand with a symphony of sound, and the stars shone bright in unfathomable numbers overhead. It was glorious, and yet I was aware that this rich nature cared not a wit about me. The same might be said of truth.

Assemblyman Zwicker, whose first slide included a quote from an astronomer, ended his talk with a quote from Carl Sagan, an astronomer who studied at the observatory I grew up next to: