Book Review: Our Green Heart

By Patsy Cotterill

Our Green Heart: The Soul and Science of Forests, by Diana Beresford-Kroeger, 2024. Canada, Random House.

Diana Beresford-Kroeger’s stated purpose in writing this book is to advocate for forests, both the conservation and planting of trees, which are vital for the health of ecosystems, climate mitigation and we humans. Her particular mission is to conserve the genetics of plants, particularly trees, of global concern, which she puts into practice on her tree farm in Ontario. 

Both worthy aspirations, and, bottom line, the book is worth reading for the nuggets of information it contains that may not be readily accessible elsewhere. But does this collection of essays work as popular science? I recognize that there is a good deal of emotion involved in our relationships with the natural world, which often impels a desire for factual information, but I found the strange mix of philosophy/spirituality and science an off-putting novelty. Beresford-Kroeger seeks to use her extensive academic knowledge, especially as a medical biochemist, to add value to our appreciation of trees with an understanding of underlying biological and biochemical phenomena. As a reader with some biological background, however, I found myself constantly trying to translate her lyrical flowery language into familiar biological concepts. I wonder what readers with no biological knowledge at all, and professional biologists, respectively, will make of this book. 

I suspect a deliberate decision was made to keep it popular, with as wide an outreach to the public as possible. I’m guessing her editor does not have a biological background and her proofreader likewise (cryptogams not cryptograms!). Hence, in the interests of popularity, a further decision was made not to explain the biological phenomena in any kind of detail or straightforward way that would allow the reader to fully understand a phenomenon. 

Likely I gained most value from the book by going to Wikipedia for further enlightenment. For example, I Googled “endogenous fungi” and went down a fascinating rabbit hole about endophytes, the bacteria and fungi that live inside plant tissues and have a significant effect on their health. Apparently, a lot of research is going on in this field because of its importance in agriculture for crop health. 

Other ideas were not so easy to decipher. In the first essay, Beresford-Kruger describes the origin of life on earth as follows, referring to the newly created rocky planet: “At first, waves of infantile infrasound, generated by molecular movement, loped along, with a seed of knowledge riding their peaks and troughs. In time, these seeds of knowledge stretched into strings, and with the blessing of symmetry, those strings danced together and shaped themselves into a spiral form, the one we now know as DNA.” Infrasound? Molecular movement? Seeds of knowledge? Consider also this statement in a later chapter entitled “The Risks of Taking Nature’s Place”: “In the warm oceans where life was born, the simplest algaes (sic), managing photosynthesis with their primitive thylakoid instruction, needed time to grow and change…..But across the ages, the thylakoid membrane evolved into the welcomed spiral of the DNA helix.” Possibly it would need a whole book and a good brain to explain that evolution, but meanwhile there is nothing on the internet to explain the connection, and I am left frustrated by an incomplete narrative. As for DNA being “welcomed”, well, I suppose this type of transposed sentiment is a technique in poetry!

Trembling aspen (Populus tremuloides), Edmonton, 2009-08-03. Photo: P. Cotterill.

On a subject about which I do know a little, the trembling aspen, I find fault. She describes aspen leaves as transparent, thinner than the leaves of other deciduous trees and “silken.” In fact, mature aspen leaves are smooth, hard, opaque and I would say relatively thick, all characteristics that I suspect are designed to reduce water loss. She describes its “trembling” character as being due to its petiole being long and “delicately designed” in balance with the blade. But what is the significance of this ability to twist easily in the wind? And can she explain how and why so many aspen leaves turn bluish-green (glaucous) as the season advances? She does, however, explain why aspen makes good paper, and recommends growing it through cloning to spare other trees. 

To the author’s credit, I did learn some currently emerging biology. Her reference to glycosides in connection with transpiration had me skeptically reaching for the Internet, but sure enough this is an area of active research, not least because of the significance of glycosides in human therapeutics. Beresford-Kroeger speculates that glycosides help to create surface tension in the xylem, thereby assisting cohesion of the water column; the Internet suggests also that they help regulate the opening of the stomata, which affects carbon dioxide exchange as well as transpiration and may contribute to energy balance in the plant. 

The author devotes a considerable amount of space to tree-emitted aerosols in the chapters “The Boreal Spring” and “Forest Bathing,” which many readers will find interesting. The smell from the resin of balsam poplar buds, as they swell and open in the spring, is truly pleasurable and no doubt conducive to endorphin production, but I am doubtful that scientists can know that the drifting oleoresin aerosols on the breeze have the multiple beneficial effects on the human body that she describes. While the commonalities in biochemistry between plants and animals are becoming clearer with research, I am leery of the anthropocentric viewpoint, any suggestion that these chemical compounds were designed for human benefit rather than for their utility to the organism itself. 

Inadequate descriptions and incomplete narratives are perhaps inevitable in a book that seeks to have popular appeal while providing some insights into the complex technicalities behind observed biological phenomena. Biochemistry is a complicated subject. Nevertheless, I feel that some judicious editing could have avoided some of the pitfalls of loose or vague writing and aided reader comprehension, even if Our Green Heart does not aspire to the rigour of some other popular science works such as The Light Eaters, by Zoë Schlanger, and Entangled Web, by Merlin Sheldrake. These attempt to authenticate science content by interviews with researchers (done to a limited extent by Beresford-Kroeger), extensive footnotes, and citations of scientific papers (lacking in Our Green Heart).

Bottom line: For those inclined to do further reading on their own, I suggest that the book is a useful jumping-off ground for exploring some up-to-date biological ideas. Readers will probably enjoy her autobiographical chapters and insights, and those with a Celtic heritage especially, her flashbacks into her life in Ireland. But perhaps a better start to understanding what truly magnificent creatures trees are, is to read a biology textbook!