An extraordinary book about trees (and people)

Trees: From root to leaf, Paul Smith, 2022. University of Chicago Press.

By any measure trees are big – some can very tall,* others have enormous volume,** and some possess great weight.*** Therefore, to do them any sort of justice in print, a big book is needed. And that’s just what Paul Smith has provided with Trees [which title is here appraised].

Largely objective…

Trees is divided into nine chapters. Although they take their names from an aspect of tree biology or ecology, each goes far beyond the science to look at various aspects of trees-and-people relationships. Accordingly, we have: Seeds [including Coconuts, Dispersal Adaptations, and Seed Banks and the Seed Cathedral]; Leaves [with Biomimicry, Tom Thomson and the Group of Seven, and Defences]; Form [also looking at Architecture, Tree Crown Mapping, and Sentience and Mythology]; Bark [with good mention of Medicines and Uses, Cork, and Tree Damage]; Wood [also considering Wayfarer’s Chapel, Use of Timber through the Ages, and Deforestation and Afforestation]; Flowers [show-casing such topics as Figs, Pollination Methods, and Flower-viewing in Japan]; Fruits [featuring Mutiny on the Bounty, Fruit-based Fashion, and Art]; and Symbiosis [that considers Screw Pine of Madagascar, Species Network, and Trees in Children’s Literature]. The book’s final chapter – Trees and Us [which covers such topics as Urban Planning, Sacred Timber Buildings and Objects, and Ecosystem Services]– is written by Yvette Harvey–Brown. Each chapter begins with a fairly solid narrative Introduction – which is often a short essay on the section’s topic that is complete in itself and where much of the biology resides. The other items in a chapter are generally short sections of text with abundant illustrations that consider more of the tree-people interactions.

The book concludes with sections on Further Reading, a listing of Arboreta and Botanic Gardens, a Glossary, and an Index. The two pages of Further Reading list several books (with accompanying notes from Smith), four scientific research papers, and five website resources (including an Encyclical from Pope Francis) that may – or may not [we are not told explicitly if that is the case for any of the items listed] – have provided sources for some of the statements made in-text. One very relevant trees-and-people book not listed by Smith, but which readers should be aware of, is The Story of Trees by Kevin Hobbs & David West.

Two pages of Arboreta and Botanic Gardens – listed by country – are useful for the book’s world-wide readership who’d like to see trees ‘in the flesh’. However, although Smith states that the list is not exhaustive, it does seem odd that neither RBG Kew nor its satellite site at Wakehurst Place are listed under United Kingdom tree collections, the more so since author Smith was head of Kew’s Millennium Seed Bank (Gregory Katz; Ruari Barratt) which is housed at Wakehurst Place. Both of those sites have great collections of trees and deserve mention; a book devoted to trees is no place for modesty. Three pages of 3-columned Glossary provide entries and definitions for words and phrases from alkaloid to xylem. The five pages of 3-columned Index entries for trees extend from Acacia to Zelkova [and, using Index entries of scientific names as a guide, a total of 139 trees are mentioned by name in the book****].

Trees is abundantly-illustrated; its approx. 300 pages of main text are probably half narrative and half pictures/graphics, which makes for a reasonably undemanding read. And, because some of the illustrations occupy whole pages, Trees is both informative and beautiful to look at; it’s where coffee table book (Tyler Chin) meets scholarly text.

Primarily subjective…

Trees is a big book with plenty of big – sometimes full-page – pictures of trees and tree-related objects, as befits the great size of many of its subjects. In appearing to ‘big-up’ trees and tree products, it is an unapologetic celebration of trees and treeness, with a blend of biology and tree-people interactions. In respect of the latter, I can do no better than echo Smith’s words: “Trees are a source of inspiration, of deep affection, spirituality and creativity. In the pages of this book, we celebrate the art and architecture that has been inspired by trees across nearly every human culture throughout history. From ancient Chinese artworks to children’s fairy tales to ultra-modern architecture, trees have been our muses, our protectors and our silent companions” (p. 130). Trees is both a well-written and a not overly-demanding read; the largest sections of text are the introductions to each chapter, but they cover such a wide range of topics that reader engagement is maintained.

There is much to commend about this book, and a lot one can learn – even those of us who have researched aspects of tree biology for many years. For example, and dramatically underlining the commercial importance of trees, Harvey-Brown reminds us that global timber exports in 2019 were US$244 billion(!). And she also tells us that humans’ use of wooden furniture goes back at least as far as 30,000 years ago. For me, one of the stand-out items that illustrates how far mankind has come in its relationship to trees and tree products is the graphic timeline of Use of timber through the ages – from firewood 1-2 millions of years ago to 3-D printed homeware in the 21^st century. And the book is pleasingly up-to-date. As evidence for this there is the revelation that leaves of the mazari palm (Nannorrhops ritchieana)**** have been used as face masks to protect against Covid-19 [see Fig. 5 in Maroof Ali et al., Ethnobotany Research and Applications 19(35); doi:10.32859/era.19.35.1-10 – which item is not listed amongst Further Reading].

All those good points notwithstanding, I have two main criticisms of the book: Minor is the illustrations/graphics, more major is the issue of evidence for facts in-text [yes, that old chestnut].

Trees contains lots of stand-alone photographs of trees and tree-relevant items. They’re great, add a lot to an appreciation of the subject matter, and I have no problem with them. Where I do have an issue is with the multi-illustration assemblages of images which quite often use artistic interpretations rather than photographs. For example, the collections of: tree seeds, dispersal adaptations, seed colours, fruits, leaf shapes, and apple varieties. As charming as the pictures used are, I believe that photographs of the actual items would have been much more informative for, and useful to, the reader. Using ‘representations’ seems a curious choice for the book’s subject matter that is eminently photographable, and is an issue that’s compounded by there being no explanation of why that particular presentation style was chosen. Additionally, it would be helpful to have scale bars to assist the interpretation of the photomicrographs on pp. 72/3.

Knowing how concerned author Smith is to ensure that what he writes is factually accurate – which we learn from an interview he gave with Christine Macaulay-Turner – we can expect that he will have sources for all of the statements of fact that he states (and hopefully that also applies to Harvey-Brown’s contribution). Therefore, having taken the considerable time and effort to verify his facts it would have been really useful to the reader – whom one likes to think would have a sufficiently healthy dose of scepticism and be keen not just to accept things on trust – if those sources were stated, and their connection to facts in-text made explicit. Whilst it’s useful to have an indication of Further Reading for interested readers to pursue matters of interest to them, such a listing is no substitute for specific sources that are tied-in to specific facts in the book. Furthermore, although one assumes that the stated Further Reading provides sources for at least some of the facts Smith states, I saw no statement to that effect. So, although Trees is a great book for ideas and inspiration, you’d need to do your own research to secure appropriate citation(s) to support any of the book’s facts you’d want to share with others.

Finally, with its intimate mix of plants and people, Trees is somewhat reminiscent of a very large version of a tree title from Reaktion Book’s Botanical series (e.g. palm, ash, and mulberry) – albeit with much more biology, and covering a greater number of species and plant families in a single publication.

Considering how important trees – and tree products – have been to humankind for millennia (and continue to be), it came as a shock to learn that it wasn’t until 2017 that we had the first complete listing of tree species. Which is compounded by the news that one-fifth of those trees that are threatened with extinction are of value to humans. Trees by Paul Smith is therefore a timely publication and an important reminder of the debt owed by humans to these magnificent natural wonders.

Book’s best intentions…

Does the book deliver what it claims? We can only answer that if we know what its intended purposes were. For that we need look no further than the book’s Introduction. There we are told that: “It is the extraordinary diversity of trees – vital to our human lives, to our planet and as a source of inspiration to the people and the cultures they build – that this book celebrates” (p. 11). Which sentiment is reinforced on p. 13: “It is the value of trees to humans that this book celebrates”. And, if you still need some assurance of the book’s mission, “The book goes far beyond the utility of trees: it is a true celebration of their existence” (p. 13). Within the constraints of what is included within its few-hundred pages, Trees certainly does deliver what is claimed. But, in providing a good deal of biology as well, it actually gives more than it appears to promise in those three quotes, which is a nice bonus.

What is – and isn’t – a tree?

Smith acknowledges that there is no universally-accepted definition of a tree (on p. 11) (although he does actually provide the IUCN definition on p. 83), which means that almost any suitably-sized woody perennial comes within the book’s domain. However, even Smith’s broad tree definition excludes plants such as the lotus (Sarah Regan) and Welwitschia (Alice Notten). It is therefore slightly puzzling that those two non-trees should be so prominently featured in the book, as 2-page items, the former in terms of its leaves’ legendary water-repellency (Jeremy Jordan), and the latter for possession of the longest-lived leaf. However, the inclusion of items about flowering plants, lichens, mosses, and ferns is legitimate – when closely associated with trees as epiphytes. And fungi will always be relevant to trees as intimate companions via their underground mycelial networks. Talking of which…

What, no mention of the wood-wide web?

Trees is full of surprises. But, one of the biggest – for me – was the absence of mention of the wood-wide web, “a term used to describe the underground network of fungi that connect the roots of trees and other plants in a forest ecosystem” (Hugh Asher). Widely-popularised by the work of such forest biologists as Suzanne Simard (Sarah Kaplan), it’s a concept – or, rather the way it’s used to imply capabilities of trees that are rather subjective and go beyond the scientifically-defensible – that’s increasingly being questioned by scientists (e.g. Justine Karst et al. in their analysis entitled “The decay of the wood-wide web?”). Despite competing claims for how one should interpret research regarding the tree-tree mycorrhizal connectedness (Gabriel Popkin; Henry), the notion of the wood-wide web has captured the public’s imagination and is one that’s very much in the media (e.g. Ed Yong; Josh Gabbatis; Tyasning Kroemer; Henry; Shiella Olimpios), and will probably be known to the book’s audience.

The existence of the wood-wide web is strongly hinted at in Trees. For example, Smith states that: “The ability of trees to ‘communicate’ with each other via electrochemical signals is comparable to neural networks and a sort of collective brain” (p. 104). On p. 254 he tells us that: “There is good scientific evidence now about how species are connected in ecosystems, not just through their reliance on each other, but also through physical connections – for example via mycorrhizal fungi, which enables chemical communication”. And on p. 88 he mentions ‘mother’ trees (which would have been the perfect opportunity to cite work of Simard, especially her book Finding the Mother Tree (Tiffany Francis-Baker). Furthermore, the book’s foreword is written by Robert Macfarlane – who has previously written at length about the wood-wide web. For those reasons I was surprised not to see it given a mention in Trees.

Some famous trees that aren’t there…

For all of the dozens of trees that the book show-cases, and given its important message of the deep connection between people and trees, Trees makes no mention of the bridges constructed from living fig trees in northern India (Zinara Rathnayake; Paul Salopek), However, the book does devote two pages – including two photographs – to a seat made of living weeping willow branches, by designer Gerardo Osio.

And other ‘famous trees’ are not featured; for example, there’s nothing about: Christmas trees (Rachael Mitchell; Penny Travers); Yddragsil, the ‘world-tree’ of Norse mythology (Daniel McCoy); the Celtic tree of life (Ciaran Vipond), the biblical tree of life (Randy Alcorn) and/or tree of the knowledge of good and evil (Harry Sanders; Justin Taylor); and the ‘survivor trees’ [https://en.wikipedia.org/wiki/Hibakujumoku] that withstood the atomic blasts that devastated the living and non-living in the Japanese cities of Hiroshima and Nagasaki during the Second World War [more here, and here].

But, the above comments shouldn’t be seen so much as a criticism of the book [it’s rarely that relevant or helpful to dwell upon what’s not there, the choice of content is up to the author]. Rather, it’s more an acknowledgement that there is such a lot to the ancient and intimate connections between people and trees that there’s still plenty more to discover (and write about). Now that the reader’s appetite for such information has been whetted by Smith’s wonderful book, one hopes they will continue that journey of tree discovery amongst the extensive tree-based literature that already exists [some of which is listed as Further Reading in Smith’s book].

Summary

Trees by Paul Smith is a beautiful book that will enthral any plant-lover, and should help to encourage the ‘plant-averse’ to appreciate trees specifically, and plants more generally. If it also creates greater concern for the plight of trees, then so much the better. Overall, Trees is a triumph of plant and people writing and information: Smith has set the bar high for all other books about trees and people.

* Shorea faguetiana (Mary Gagen; Alexander Shenkin et al. (2019) Front. For. Glob. Change 2:32. doi: 10.3389/ffgc.2019.00032), “the tallest tropical tree, up to 100.8 m (331 ft) tall” (p. 83 in Trees by Paul Smith).

** By trunk volume, the giant sequoia (Sequoiadendron giganteum) known as General Sherman is the largest “at 1,487 cubic metres (52,500 cubic feet)” (p. 85 in Trees by Paul Smith).

*** “Trees … can weigh more than 1,000 metric tonnes (985 imperial tons) – that’s more than six times the weight of a blue whale” (p. 11 in Trees by Paul Smith).

**** Interestingly, in searching for more information about this plant on the interweb, the most common spelling for the specific epithet of its scientific name is ritchiana (e.g. Palmpedia, Plants for a Future, PALMweb, Pl@ntNet, Wikipedia, and All About Palm Trees). However, the version provided in Smith’s Trees – ritchieana – appears to be correct as confirmed by the Plants of the World Online database of plant names hosted by Kew, and World Flora Online. Oddly, Nannorrhops ritchieana is not included in the Index for Trees, so there are at least 140 tree species name-checked in that book…