Forest ecologist's work highlights role `mother trees' play in ecosystem health
Forest ecologist Suzanne Simard has devoted her career to groundbreaking research into understanding the rich communities of biodiversity formed in healthy forests beneath the canopy of what she has dubbed mother trees.
Simard weaves the story of that journey through her bestselling book Finding the Mother Tree: Discovering the Wisdom of the Forest, so she has an understanding of how forestry has contributed to B.C.'S serial crises of catastrophic wildfires and devastating floods.
And that research about the importance of “mother trees” offers ideas for how forestry can also be used to rehabilitate forests in ways that can mitigate future climate impacts.
“Definitely, forestry has played a big role in what's happened,” said Simard, a professor of ecology in the University of B.C.'S faculty of forestry.
With the public's attention focused on climate change and forestry though, Simard also senses “we're at that moment” for change.
“This is the opportunity for change, because we're in crisis ... with the floods and the fires,” she added. “And it is during crisis that you have the opportunity to shape change.”
The province is in the middle of some changes. This fall, Forest Minister Katrine Conroy introduced changes to the Forest and Range Practices Act to give factors such as biodiversity, forest health and Indigenous involvement in decision-making higher priority. Then in November, she unveiled a plan to defer more old-growth logging on a path to protect critical old-growth habitat.
“The first thing is, clear-cutting should be off the books going forward,” is Simard's advice. “(Logging) should be partial cutting, where we do cut, and no more than 25 per cent of a watershed in view of these floods.”
And Simard's own long-term research initiative, The Mother Tree Project, supported by the Natural Sciences and Engineering Research Council and Forest Enhancement Society of B.C., explores which combinations of logging and forest retention lead to more resilient forests.
That research has shown that trees co-operate to share resources more than they compete for them, which was long assumed to be the case. And mother trees, the oldest and biggest in a forest, are the most important contributors to that process.
When it comes to clear-cuts, forestry companies have long been obligated to replant what they log, and Simard said forest ecologists have learned a lot about matching the right tree species to specific sites. “That's another excellent thing that B.C. has become very good at,” Simard said.
But she argues that B.C. still prioritizes timber production in reforestation through so-called freeto-grow regulations, which require firms to weed out non-conifer species such as aspen and birch with the use of herbicides.
“That mindset has to go,” Simard said. “When you reduce the biodiversity of an ecosystem, which you do when you're spraying or cutting out deciduous trees, you're actually reducing the resilience of that ecosystem.”
Whether conifer trees, such as lodgepole pine or Douglas fir, are freely growing isn't the best measure, she added, “because what you really need is just a healthy group of species.”
Simard said healthy soils play a bigger role in storing carbon than most people realize.
Simard pointed to a World Wildlife Fund and Canadian Forest Service study that estimated 95 per cent of Canada's sequestered carbon is sunk in soils and peatland, just five per cent is above ground in the trees.
“And we're disturbing that soil pool in a huge way,” she said. “We lose about 60 per cent of forest-floor carbon, according to our measurements, from mechanized (logging) and that loss will take hundreds of years to recover,” Simard said.
The research Simard is leading through the Mother Tree Project is also demonstrating the role that retaining older trees during logging plays in regenerating forests.
Over decades, her experiments have shown how trees share resources — carbon, nutrients, water — through their roots along intertwined strands of mycelium in a symbiotic relationship with forest fungi.
And mother trees, the oldest, are the most important, Simard said.
“So they have big crowns and high photosynthetic capacity, because they've got lots of leaf area,” Simard said. “They are the (trees) that are like fountains into the soil ... just shovelling energy below ground.”