The ‘Mother Tree’ idea is everywhere — but how much of it is real? And Variable Tree Retention as a Current Practice, But Maybe Not in BC

It’s always fun to look at another scientific controversy around trees and forests.  TSW had posts on various facets of this issue, here, here and here. Thanks to Nature for making this article open source!

A brief recap:

Their concerns lay predominantly with a depiction of the forest put forward by Suzanne Simard, a forest ecologist at the University of British Columbia in Vancouver, in her popular work. Her book Finding the Mother Tree, for example, was published in 2021 and swiftly became a bestseller. In it she drew on decades of her own and others’ research to portray forests as cooperating communities. She said that trees help each other out by dispatching resources and warning signals through fungal networks in the soil — and that more mature individuals, which she calls mother trees, sometimes prioritize related trees over others.

The idea has enchanted the public, appearing in bestselling books, films and television series. It has inspired environmental campaigners, ecology students and researchers in fields including philosophy, urban planning and electronic music. Simard’s ideas have also led to recommendations on forest management in North America.

What’s the role of scientists in presenting their and others’ work?

Then, a third academic, mycorrhizal ecologist Justine Karst, took the lead. She thought speaking out about the lack of evidence for the wood wide web had become an ethical obligation: “Our job as scientists is to present the truth, as close as we can get to it”.

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Simard says of her critics.. “They’re reductionist scientists,” she says when asked about criticism of her work. “They’ve missed the forest for the trees.” She is concerned that the debate over the details of the theory diminishes her larger goal of forest protection and renewal. “The criticisms are a distraction, to be honest, from what’s happening in our ecosystems.”

It seems to me that there are robust and fun scientific discussions to be had.  As depicted by this journalist (Simard might not have been quoted accurately), Simard thinks having discussions about science distracts us from what seems like advocacy. 

Roger Pielke Jr. has written (much, here’s one example) about what he calls “stealth issue advocacy” in the scientific community.  This doesn’t seem stealthy at all. It seems like sometimes you have to pick a lane between science and advocacy; and I’d prefer if scientists picked science.
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There’s a description of the differing scientific views. There are technical differences, and even apparently emphasis or focus differences.

Johnson’s view is that it “makes complete sense” that there are CMNs linking multiple forest trees and that substances might travel from one to another through them. Crucially, he says, this is not due to the trees supporting one another. A simple explanation, compatible with evolutionary theory, is that the fungi are acting to protect the trees that are their source of energy. It is beneficial for fungi to activate a tree’s defence signals, or to top up food for temporarily ailing trees. Pickles, who spent six years working with Simard before moving to the University of Reading, UK, says Simard’s ideas are not incompatible with competition, but give more weight to well-known phenomena in ecology, such as mutualism, in which organisms cooperate for mutual benefit. “It’s not altruism. It’s not some outrageous idea,” he says. “She certainly focuses more on facilitation and mutualism than is traditional in these fields, and that’s probably why there’s a lot of pushback.”

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Simard maintains that her critics attack her in the academic literature for imagery she has used only in public communication: “I talked about the mother tree as a way of communicating the science and then these other people say it’s a scientific hypothesis. They misuse my words.”

She argues that changing our understanding of how forests work from ‘winner takes all’ to ‘collaborative, integrated network system’ is essential for fixing the rampant destruction of old-growth forest, especially in British Columbia, where her research has focused. Indigenous cultures that have a more sustainable relationship with forests have mother and father trees, she says — “but the European male society hates the mother tree … somebody needs to write a paper on that”. “I’m putting forward a paradigm shift. And the critics are saying ‘we don’t want a paradigm shift, we’re fine, just the way we are’. We’re not fine.”

But does a “network system” “Indigenous culture-based” worldview lead us anywhere different in practice than the “ecological forestry” of the lower 48? Can the same kinds of practices be invoked, or even carried out, without a what we might call a “myco-centric” worldview? And if everyone used VRH, what would the scientific controversy be about.. would it be more theoretical (how important is mutualism vs. competition generally?) or more specific (more mycological experiments in the field?).

But what about variable retention harvesting as espoused by Jerry Franklin? In this open-source paper by Franklin and Donato (2020) (from the abstract):

Variable retention harvesting evolved in the Douglas-fir region of the Pacific Northwest gradually in response to increasing dissatisfaction with the ecological consequences of clear-cutting, from the standpoint of wildlife habitat and other important forest functions. It is a harvesting technique that can provide for retention (continuity) of such structures as large and old live trees, snags, and logs. Variable retention is based on the natural model of the biological legacies that are typically left behind following natural disturbances, such as wildfire, wind, and flood

This approach actually sounds more holistic (plants, animals, viruses) than one solely focused on CMNs, while providing opportunities for CMNs. Franklin seems to be in the camp of aggregated variable retention rather than dispersed. Conceivably the Mother Tree approach would be dispersed, which might be good for CMNs and possibly not so good for other ecosystem values.

According to Franklin and Donato’s historical narrative, aggregated retention was seen to be effective at conserving a broad array of biota around 1987 with experiments by the Plum Creek Timber Company. Perhaps these ideas did not migrate north to BC? But later in the history there is mention of the Clayoquot Sound Science Panel.

. This was part of a governmental response to major social disorders over the logging of old-growth forests in this region led by Native Americans (known in Canada as First Nations) and participated in by other Canadian citizens. The science panel conducted its activities and completed its report over the next year (Scientific Panel for Sustainable Forest Practices in Clayoquot Sound 1994). The Clayoquot Sound Science Panel recommended adoption of the “variable-retention silvicultural system” for all timber harvesting on Crown Lands in the region. The panel actually created the term “variable retention” to reflect the reality that the amount and other details of retention should vary depending upon management objectives and the nature of the stand being harvested. The panel recommended that harvests should “retain a minimum of 15% of the original stand on all cutting units … [excepting] very small cutting units” and that the retention should “retain a representative cross-section of species and structures of the original stand.” In areas with very high values for resources other than timber (such as wildlife habitat, slope stability), the panel recommended retention levels of at least 70%. Hence, the Clayoquot Sound Science Panel contributed significantly to the concept as well as the name “variable retention.” The panel’s recommendations also helped set the stage for MacMillan-Bloedel Corporation’s decision to replace clear-cutting with variable retention a few years later (Beese et al. 2019).

Anyway, this post started out by being about mycological networks and the scientific controversies therein, and that article is certainly interesting. But I also thought the Franklin/Donato paper, being historical in perspective, also deserves a look by those among us involved during those time periods. And am I the only person who remembers “big messy clearcuts”? Was that the same as “variable retention” or different?