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An ecologist’s memoir emphasizes the interdependencies of life

Finding the Mother Tree: Discovering the Wisdom of the Forest

Suzanne Simard
Knopf
2021
368 pp.
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The role of mutual aid in the history of life has been a persistent countertheme to the survival of the fittest—from the earliest studies of animal sociality to the discovery that key eukaryotic organelles descend from intracellular symbionts. In Finding the Mother Tree, forest ecologist Suzanne Simard recounts a career spent seeking out the practical implications of life’s interdependencies.

Plants’ symbioses with soil microbes are textbook examples of mutual aid. Plants may have first colonized land with the help of mycorrhizal fungi, which infiltrate roots to trade water or nutrients for the sugars produced by photosynthesis. Ectomycorrhizal fungi, a subset of mycorrhizae that establish commerce without penetrating root cells, are particularly important partners for a wide diversity of tree species. For a fragile seedling, linking into the web of fungal hyphae that lace through the richest layer of soil provides a sort of surrogate root system.

Over decades of research, Simard has built a body of evidence that mycorrhizae do not simply support trees but actually connect trees to one another. Using radioactive isotopes, she has tracked the movement of nutrients through fungal linkages, both between trees of different species and between older “mother trees” and nearby seedlings of the same species. Simard argues that fungus-mediated flows of mutual aid and information let forests respond to their environments—communication and intelligence, if not as we know them.

Simard’s interaction with fungal soil networks stretches back to a childhood spent exploring the woods of British Columbia as a fourth-generation descendent of homesteaders and loggers. She recalls having a nonmetaphorical taste for dirt—particularly rich humus, flavored with fallen leaves and shot through with industrious fungi. Some of the book’s best passages are loving descriptions of time in the woods, drinking in the vanilla scent of ponderosa pine, tromping through thick-growing wildflowers, or burrowing into the soil to find a fungal body and trace its hyphal links from one tree to another.

Simard gives similar attention to the design and execution of key experiments, from logistical setbacks to the thrill of early results. Readers should come away with a firm grasp of the evidence underlying Simard’s vision of the interconnected forest, and scientists will take inspiration from her wry descriptions of the hurdles of fieldwork.

An early job with a logging company paved the way for her to join what had become a family vocation, but Simard rapidly became disillusioned with industrial forestry. British Columbia licenses forests to loggers on the condition that they replant and ensure that replanted seedlings persist until big enough to be “free to grow” without serious competition from shrubs and trees that would otherwise spring up around them. Weeding and herbicide were prescribed to speed replanted tracts, but Simard recalls comparing sickly seedlings in a failing replanting to healthy young trees in nearby undisturbed forest: the former, barely any better rooted than when they were first put into the ground; the latter, deeply tied into the mycorrhizal web. Pushing for forestry that better parallels natural succession became her driving motivation.

That drive can sometimes give Finding the Mother Tree a feeling of tunnel vision. Simard’s family history spans fascinating transitions in Canadian society, from the arrival of European settlers to the development of industrial forestry to an economy in which the descendants of loggers work as university professors. Yet, apart from brief references to First Nations peoples displaced by white settlers, this history goes largely unexamined. Similarly, the book’s discussion of scientific responses to Simard’s early discoveries mentions in passing that some objections were raised in the context of a larger scientific debate about the relative roles of competition and mutual aid in living communities, but that debate is left largely unexamined.

Nevertheless, science is as much about burrowing into a topic to trace the ramifications of a single question as it is about positioning that question within a global context. If Simard could be accused of missing the forest for the trees, her response would likely be that a forest can only be understood as it grows, one tree joining another.

About the author

The reviewer is at the Department of Biology, California State University Northridge, Northridge, CA 91330, USA.