Tame Trees and Wild Tigers

By Pamela Walker

Published in Take 5 Magazine, March 2022

Scientists used to believe that trees compete with each other for light, water, and other resources. All that has changed now, thanks to the work of Dr. Suzanne Simard, and other forest ecology scientists. It is now known that forests live cooperatively, caring for their own offspring, other trees of the same species, and even different species of tree in the same forest.

Like neighbours lending a cup of sugar when their larder is full, birch trees are known to give carbon to Douglas fir trees when their leaves fall off and they have food to spare. Alternately, when spring comes and their leaves burst out, a hungry deciduous tree will ask for food back from its neighbouring conifers. The trees in a forest are now known to move their roots to make way for siblings who are squished for space. And like in any good neighbourhood, they have a kind of Block Watch Program that they use to warn each other of predators in the ‘hood, such as carpenter ants, powder post beetles, or munching caterpillars. 

Trees do all this communicating with the help of the Wood Wide Web, a term coined to explain the mycorrhizal network and underground root system that facilitates interactions between the trees and plants. The fungus below the ground, along with the tangled mats of roots, acts much like a telephone operator in the good old days, when phones were wound up with a crank. Using fungus and wood instead of electrical wiring, this tree is connected with that tree, and that tree is connected with that bush.

At this point you may be asking “Is this really true?”, and if it is, how did Dr. Simard discover it? These are good questions. And the answer is simple, really. 

Dr. Simard put carbon isotopes into the ground beside one tree and used them like a tracking device on a tiger to see where it moved around. As any gardener knows, plants love carbon, and because this was a specific kind of carbon that did not appear in the earth samples she had taken, she was quite sure that wherever they found those isotopes again, they would be the same ones she had introduced to the soil herself.  Just as she had thought, the carbon isotope was found far away from where she had stuck it in the soil, at the roots of a smaller, struggling tree. Through more experimentation like this, Simard discovered that there were what she called ‘Mother trees’ that seemed to be responsible for ensuring that nutrients and water are delivered to the many different trees in the forest. Even more surprisingly, she discovered that the Mother trees know which seedlings in the forest come from her seeds, and these are the ones she cares for the most.

Simard’s findings have had a startling effect on the forest industry, and on the study of ecology itself. It turns out that we are wrong to believe that forests fight for limited resources. Instead, they cooperate with each other to ensure the survival of the forest as a whole. The takeaway from all this research is that instead of clearcutting—as we have done in the past—it is important to leave many larger trees that can nourish the new forest, just as wild tigers will care for their cubs. 

For more on all this, check out Simard’s memoir Finding the Mother Tree (2021), or stay tuned for the movie of the same name starring Amy Adams. We have asked Dr. Simard to join us for one of our YES Zoom meetings, at which she has agreed to speak, although a date has yet to be set.