Beware of “Mommie Dearest” Trees?

This article by Jenn Bernstein and Justine Karst is worth a read.  You can sign up for Damage magazine for free.

After I was taught at a church gathering that Mother Tree was absolutely true stuff (and the gates of my own knowledge did not prevail against it), I decided to look further.

First.. extraordinary claims require extraordinary evidence.  There’s a genetic component to be a mother.  If not, if they are adopted children, then perhaps the less emotionally compelling term “nurse tree” is more accurate.   But if there is a genetic component, how does the Mother Tree know which ones are her seedlings?

Don’t you have to propose,  and test a mechanism before you make this claim?

This seems to be a feature of current scientific norms. In old science, we did experiments to understand mechanisms, and we used to say “correlation is not causation”.  In today’s science, we leave the mechanisms to be explored by someone else, if there’s funding, but long after major findings are trumpeted by the university communications office and then the popular press.

Second (and I think that this step is often skipped), imagine an experiment that would test this idea.  How many species? How many different ecosystems?  How would you design it?  How would you handle the mycological aspect?  Would you do it in pots (not real) or on a forest site (way too many variables)?  Would you transplant seedlings or seed directly? How long would you wait before making conclusions? If your mind boggles. then it’s time for:

Third, if someone is making extraordinary claims based on not exactly impressive evidence (say, the genetic aspects of this work, which I have reviewed), then the right thing to do, in my view, is to jointly design experiments to further test the claims , with all the key disciplines and with skeptics. The sense would be joint curiosity, not defense.  There is no place for, as we have seen with this research, university administrators dissing the intentions of skeptical scientists (which now includes me. Hint: I am a supporter of all scientists working in good faith, and obviously don’t have a COI).  It’s about mutually learning about the world.. or is it about institutional hegemony or ideology or a kind of scientific popularity contest? And as we have seen and described in this post, leaving large trees is not a new concept and seems to be BAU in many quarters, known as variable retention and originally thought to be good for wildlife.

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“Mother Trees” are described as the biggest, oldest trees in a forest. The metaphor was introduced in 2016 by forest ecologist Dr. Suzanne Simard. Despite having both male and female organs, these trees were dubbed “mothers” due to what Simard perceived to be their mothering behavior. Through common mycorrhizal networks, formed when fungi physically connect roots of the same or different plant species, Mother Trees are said to share resources with their seedlings, directly assisting in the survival of their kin. The story goes as far as to say that when “Mother Trees—the majestic hubs at the center of forest communication, protection, and sentience—die, they pass their wisdom to their kin, generation after generation, sharing their knowledge of what helps and what harms, who is friend or foe, and how to adapt and survive in an ever-changing landscape.” In her book, Simard argues that this kind of nurturing and caring dynamic has been obscured by the historic dominance of forestry by men, who see competition instead of cooperation.

Simard’s promotion of Mother Trees in forest conservation has been recognized as “revolutionary” and “pioneering.” Her TED Talk “How Trees Talk to Each Other” has been viewed over 5 million times.

Despite the clear popularity of Simard’s portrayal of forest dynamics, there are three crucial problems with metaphors that naturalize the relationship between women and the environment. First, metaphors that relate to nature and gender have highly problematic implications for gender equality and cultural progress. Second, the Mother Tree metaphor provides little guidance in addressing today’s most pressing forest management challenges. And finally, fusing normative goals with scientific practice risks the distortion of science in deference to a self-proclaimed sense of moral authority.

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Challenging Mother Trees

Metaphors bridge the unknown with the known to clarify concepts and establish meaning. They’re a powerful literary device that emerges from uncertainty to connect with understandings when there is not yet more precise terminology. A tree’s relationship with common mycorrhizal networks has courted metaphors because of our limited understanding of how these tree-fungal networks function. Interactions among trees connected below ground have been likened to the Internet (“wood-wide web”), and given their potential ability to distribute resources within a forest community, they’ve even been cast in political terms (“socialism in soil”).

Despite the Mother Tree metaphor having cultural resonance, many of its claims are dubious, untested, inconclusive, and downright false. For example, core to the Mother Tree narrative is the idea that common mycorrhizal networks mediate belowground resource transfer, enabling the Mother Tree to help her seedlings survive. But whether common mycorrhizal networks actually function in this way has been disputed for 25 years. The narrative also implies that seedlings should be more abundant and grow better when closer to Mother Trees, but some researchers have concluded the opposite, at least for pine trees in boreal forests.

Recently, a number of critical commentaries have been published about the basic metaphor, calling into question the mechanisms purported to facilitate nurturing of seedlings by Mother Trees. In the most recent experiment to date, there was “no evidence of biologically significant carbon transfer” between neighboring tree seedlings that shared fungi in common. Many in the forest management community have simply ignored the idea altogether.

And with good reason. Like all organisms, trees vary in how they respond to other species. They can be in competition with each other for water, light, and nutrients, depending on the characteristics of each forest ecosystem. These relationships vary significantly between climatic zone, forest composition, successional stage, and management regime. Uncertainty, context-dependence, and inconclusive results from this difficult-to-study system are left behind when mycorrhizal trees in a forest are conceptually morphed into Mother Trees. Might there be just as many Mommie Dearest Trees as Giving Trees?

Despite such gaps, the popular media has been credulously fascinated with Mother Trees. A National Geographic video depicts trees in old growth forests signaling distress to each other through a common mycorrhizal network. This idea is based on a single experiment done on seedlings grown in pots in a greenhouse—a far cry from an intact forest. The idea that dying Mother Trees send their resources through mycorrhizal networks to nearby seedlings has never been tested in a forest.

Nevertheless, the Mother Tree story has been embraced by media organizations such as BBC and PBS, resulting in children’s books, documentaries, and pushes to change forest management. It appears irrelevant to these communities that significant parts of the story are based on little to no peer-reviewed research.

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