The Nature of Oaks: The Rich Ecology of Our Most Essential Native Trees

 In Book Reviews

A Review of Current Publications for the Naturopathic Industry 


Today is Earth Day, so it felt appropriate to take the morning off and volunteer for the local roadside litter clean-up efforts. It was a sunny morning, and the blustery wind that had kept us homebound for the last few days had let up. So we spent several hours outdoors, collecting the flotsam and jetsam of American throw-away culture from the public road that we use to go to the post office. Up until recently, everything was snow-covered, and even now that the snow is melted, we drive past so fast that one doesn’t see how much litter there is. It was an interesting exercise, as I know little about the inner thought processes of the sort of people who think it’s permissible to litter the roadside. They appear to smoke a great many cigarettes with non-degradable plastic filters, drink a great deal of beer (with a decided preference in this part of the woods for Bud Lite), and like a variety of alcoholic beverages that come packaged in single-serving plastic bottles (with a trend toward Canadian Club). They may add these to large soft drinks purchased from a fast-food franchise in the next town, as there were a number of large single-use plastic cups with lids and straws. 

The Mighty Oak: A Keystone Plant 

The highlight of the day was seeing the many acorns starting to sprout along the roadside, sending their taproots out on a search for the earth’s center. The road is pretty much lined with oak trees down where it crosses the creek by the lake head, and the thought of thousands of sprouting acorns brought enough joy to outweigh the despair of sharing our world with people who are happy to fill it with trash. I’m all about acorns and oak trees these days, having recently read Douglas Tallamy’s new book, The Nature of Oaks. Dr Tallamy is an entomology professor at the University of Delaware and has written what I think is a marvelous book, the sort of “nature book” that one reads slowly in order to savor it. The book is, as the title suggests, about oak trees and how in most North American forests they are the keystone tree that supports the majority of insect, animal, and bird life, keeps the water clean and the soil moist, and fosters a diversity of life more so than any other species of tree. These are all things I had never had reason to appreciate before. 

Entomology is the study of insects, not trees. Years back, Dr Tallamy became fascinated by the role oak trees play in a forest because of the many insects that depend on them, caterpillars, in particular. Caterpillars are the fuel that powers the food web that feeds most inhabitants in a forest. Most of us don’t tend to think about things like this; we have other worries. We worry about big things, like climate change or systemic racism and how it relates to people. 

Tallamy seems to worry about the little things, the tiny things, the things that make the world what it is. He reminds us that insects and the birds that feed on them are at a crucial juncture in our world. “…We have removed more than half of the forests on earth and, not surprisingly, insect populations have declined globally by at least 45% since 1979. And again, it should be no surprise that with insect declines come bird declines. There are now 3 billion fewer birds in North America than there were just 50 years ago…” As a result, 430 bird species are now considered at risk of extinction. Diversity is important, not just in our human populations and cultures or in our gut microbiome, but also in the species that populate our planet. 

We have made it incredibly hard for some species to continue to exist. There are large differences between plants in their capacity to support insects, both in variety and quantity. The biggest difference is between native and non-native plants. “We” have introduced a great many non-native plants without thinking about the consequences. Plants make chemicals to dissuade insects from eating them (these are phytotoxins to insects, phytonutrients for people). Insects have evolved tolerance to these chemicals, such that they can feed on 1 or 2 specific native plant species. Tallamy writes, “Most insects have become very good at eating a few plants but are completely unable to eat most plants.” The food web depends on insects that feed on native plants. However, often there are no local insects capable of feeding on non-native plants, so those plants bring nothing into the food web. A few native plants are referred to as keystone plants because they supply the majority of the food that enters the web. A few plant genera supply 75% of the food eaten by insects that are, in turn, eaten by birds. In most areas, the keystone plants, in order of the variety of insects fed by them, are oaks, cherries, willows, birches, hickory pines, and maples.  

In the United States there are 897 caterpillar species that depend solely on oak trees. Maples support 295 species and land in second place in the caterpillar competition. It’s not just caterpillars and birds. An oak tree produces acorns – an estimated 3 million acorns over an oak tree’s lifespan – which in turn feed other animals. Oak leaves win the contest when it comes to feeding the microorganisms of the forest floor. Oak leaves are slow to decay and thus provide a lasting mulch long after other leaves have disintegrated, supporting a greater abundance of life underfoot. Oak trees enhance the biodiversity of a locale more than any other plant.   

I used to think that if you want to help birds survive the winter, you fed them birdseed. This is because my 4th-grade teacher, Mrs Warner, imposed a “bird tax” on each of us students, which went toward purchasing bird seed. We “volunteers” tramped out in coats and galoshes every day during the winter to replenish her bird feeder with our seed. Tallamy writes that only a rare few bird species can survive on seeds. Most songbirds in North America depend primarily on insects for food; seeds and berries only occasionally supplement their diets. Many species cannot digest seeds at all.  

If we value having birds in our world, we want oak trees growing near us to supply the insects for birds to eat. Similar arguments can be made for clean water, clean air, and all the rest of the things we value in our natural environment. 

Repairing the World  

Tallamy’s book is fascinating reading and a pleasant departure for me from reading about cancer and other diseases. His general approach to life is to take careful note of the things he doesn’t understand – mysteries, as he calls them – and then to observe carefully until he can explain them. It is his ability to see the world so closely that comes across in reading his writing and which left me envious, wishing I could mimic his way of seeing the world. I suppose this is what one should expect from a professor of entomology, but it’s an uncommon trait to marvel at the world these days, one we would all do well to emulate. Each chapter of Tallamy’s book tells of some interaction between oak trees in the world that left me marveling. A marvelous book filled with marvelous stories. 

Even before finishing Tallamy’s book, I started collecting and planting acorns in our woods. Reading the book convinced me that doing so can alter a forest for the better. That’s about the best one can ask for from any pursuit – changing the world for the better. Thinking that we can give Nature a helping hand isn’t how we generally approach it. We tend to have a faith that left totally to its own accord, Nature will make the best choices. We prize wilderness, places where Nature is left to its own to restore and maintain the balance of her biosystems. That belief isn’t held everywhere. Years ago, Michael Pollan, in his first book, Second Nature, examined our American hands-off-approach and compared it to the European-style approach, which involves active stewardship. Pollan challenged the way I see the world. 

Tallamy’s oak book has done more than change the way I see things. He has me actively trudging through the forest and taking pleasure in doing so. If a good book changes the way we see the world, a really good book changes what we do in the world. 

For me, planting acorns is deeply pleasing. The world needs more trees for a thousand and one reasons. Tallamy will leave you certain that for all the reasons trees are good, oaks are better. Planting acorns touches on the idea of a “purpose-driven life” that Viktor Frankl wrote about in Man’s Search for Meaning. Being actively engaged in doing something one views as beneficial fosters the sensation of purpose and meaning. Feeding the forest ecosystem, helping the forest mature into long-living hardwoods, creating greater diversity and complexity of animal life, believing that something one has done will endure into the future and leave the world even a smidgeon better, what more can one ask for after this last year we’ve endured? This entire acorn business is giving me such satisfaction that I’m pondering the logistics of how to give away acorns to patients with instructions to “make the world a better place.” What is good for the world may also be good for the person. 

Like any new convert to a cause, I’ve been sharing my oak tree enthusiasm with friends and colleagues. One dear friend, with whom I’ve kept in touch since high school and who ended up a horticulturist of some note, wrote back that she too has been planting sprouted acorns and, much to my relief, has gotten good results. “… So you should have made great progress of repairing the world – tikkun olam, one tree at a time.” 

That phrase, tikkun olam, is Hebrew for “World Repair.” The term originated in the 16th century with the Kabbalist, Isaac Luria. It encapsulates a complex conception of Jewish mysticism, which I will forego detailing here. Suffice it to say that what Luria’s followers mean by repair is the restoration of the light of the divine to its proper place. In modern usage, tikkun olam usually describes working to improve conditions in this world, usually with a focus on social justice or environmental action. Planting acorns may be as close to tikkun olam as I’m going to get.  

This same friend also pointed out, “There is great genetic variation in oaks, even within a species. So, pick a tree you like especially well. A venerable tree…” This concept that distinct genetic variation exists between individual oak trees is probably what we’re alluding to when we say that “an acorn doesn’t fall far from the tree.” Venerable Trees is actually the title of a book by Tom Kimmerer about his efforts to save American chestnut trees from extinction – a book that I’ve added to my reading list.  

Up until now, I’ve been planting acorns from our neighbors’ trees; convenience has determined which acorns I plant. This idea of searching out specific “venerable trees,” and selecting their acorns purposefully, adds another layer to my activity. The idea has me looking at each oak tree as a distinct individual and noting what sets it apart.   

Tallamy’s book is a pleasant read, one that may change the way you walk through the world and even put you on the lookout for venerable trees. Like me, you may find yourself carrying acorns in your pocket. 


Title: The Nature of Oaks: The Rich Ecology of Our Most Essential Native Trees 

Author: Douglas W. Tallamy 

Publisher: Timber Press 

Available from: Amazon; various booksellers 

Pages: 200 

Style: Hardcover, eBook, Audio CD 

Copyright: 2021 

MSRP: $23.16 Hardcover; $9.44 eBook; $16.89 Audio book 

Jacob Schor,ND, FABNO graduated from NCNM in 1991 and has practiced in Denver, CO, ever since. He has been active in state association politics, taking his turn as president of the Colorado Association of Naturopathic Doctors and Legislative Chair. Dr Schor has also held leadership positions in the Oncology Association of Naturopathic Physicians, served on the AANP Board of Directors, and chaired the AANP’s speaker selection committee. For the past decade he has been the Associate Editor of the Natural Medicine Journal, and is a regular contributor to the Townsend Letter.  

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