By Peter Wohllenben
Greystone Books; 2021
Do trees have heartbeats? That certainly sounds like the sort of question that would intrigue and inspire The Hidden Life of Trees author Peter Wholleben. And indeed he devotes a chapter of his latest book to the subject, in addition to taking his title from it.
Trees do not, of course, have hearts, and thus don't have literal heartbeats. But, Wholleben points out, what blood is to people, water is to trees, and thus they need something that performs a pumping function similar to the heart. How exactly they pump water throughout their huge bodies is, somewhat surprisingly, still a mystery,. But Wohllenben points, as he so often does, to new research, this bit from a team of international scientists who noticed that a particular tree hung its branches lower at night. Further investigation of more trees discovered that their branches similarly changed positions every three to four hours. Could they be doing this in order to pump water throughout their bodies? Did the scientists discover the heartbeat of trees?
If so, it would make a certain amount of sense that a tree's "heart" beats only once ever few hours, while human beings' hearts beat somewhere between 60 and100 times a minute; it would be one more illustration of the vast difference in the way trees and humans experience the passage of time. Trees are much, much slower in every respect from human beings, from how long it takes them to react to stimuli to how long their lifespans are.
Readers of Wohlleben's previous books will find that Heartbeat is very much more of the same, and will likely be pleased with the discovery, seeing how well-received his earlier books were. As with Secret Life of Trees and The Inner Life of Animals, each chapter is more or less standalone, a complete short, incredibly readable essay of its own, to the extent that a reader can easily pick it up and set it down at their own rate, and almost pick any chapter at random to read, and read the chapters of the book in any order, really.
Each of these generally begins with a question or observation—Why is the forest green, for example—and then Whollenben tackles it, in the process calling on personal anecdotes from his own life among trees as a forester and modern research about the nature of plants and trees. Some passages of the book build upon one another, as in the early chapters where he takes each of our six senses in turn and discusses how they relate to the forest, or later when he recounts various trips to endangered forests where activists are trying to preserve them.
As with his previous works, Heartbeat of Trees challenges the way we think about trees, offering many new insights that make it difficult to just walk by them on the street without thinking of them as rather dynamic and incredibly strange living things ever again.
As for the climate crisis, it haunts the background of many sections of the book, and comes to the fore on a chapter on climate change, in which he reiterates forests power to cool the climate and discusses the folly of thinking of wood as a carbon neutral fuel source. He also notes that we need to start thinking more seriously about the world as an ecosystem in which we are a part, rather than the traditional separation we do where we think of the environment as something apart from us.
"The realization that we are still a part of this wonderful system and that we function according to the same rules as all other species is, thank goodness, gradually making headway," he concludes his introduction. "And it's only when it comes to the fore that conversation can be effective—that is to say, when we realize that what we are conserving is not just other forms of life but, first and foremost, ourselves."
