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The Social Life of ForestsTrees appear to communicate and cooperate through subterranean
networks of fungi. What are they sharing with one another?
By Ferris JabrPhotographs by Brendan George Ko
The Social Life of Forests – The New York Times https://www.nytimes.com/interactive/2020/12/02/magazine/tree-…
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As a child, Suzanne Simard often roamed Canada’sold-growth forests with her siblings, building fortsfrom fallen branches, foraging mushrooms andhuckleberries and occasionally eating handfuls of dirt(she liked the taste). Her grandfather and uncles,meanwhile, worked nearby as horse loggers, usinglow-impact methods to selectively harvest cedar,Douglas fir and white pine. They took so few treesthat Simard never noticed much of a difference. Theforest seemed ageless and infinite, pillared withconifers, jeweled with raindrops and brimming withferns and fairy bells. She experienced it as “nature inthe raw” — a mythic realm, perfect as it was. Whenshe began attending the University of BritishColumbia, she was elated to discover forestry: anentire field of science devoted to her beloveddomain. It seemed like the natural choice.
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By the time she was in grad school at Oregon StateUniversity, however, Simard understood thatcommercial clearcutting had largely superseded thesustainable logging practices of the past. Loggerswere replacing diverse forests with homogeneous
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plantations, evenly spaced in upturned soil strippedof most underbrush. Without any competitors, thethinking went, the newly planted trees would thrive.Instead, they were frequently more vulnerable todisease and climatic stress than trees in old-growthforests. In particular, Simard noticed that up to 10percent of newly planted Douglas fir were likely toget sick and die whenever nearby aspen, paper birchand cottonwood were removed. The reasons wereunclear. The planted saplings had plenty of space,and they received more light and water than trees inold, dense forests. So why were they so frail?
Simard suspected that the answer was buried in thesoil. Underground, trees and fungi form partnershipsknown as mycorrhizas: Threadlike fungi envelop andfuse with tree roots, helping them extract water andnutrients like phosphorus and nitrogen in exchangefor some of the carbon-rich sugars the trees makethrough photosynthesis. Research had demonstratedthat mycorrhizas also connected plants to oneanother and that these associations might beecologically important, but most scientists hadstudied them in greenhouses and laboratories, not inthe wild. For her doctoral thesis, Simard decided toinvestigate fungal links between Douglas fir andpaper birch in the forests of British Columbia. Apartfrom her supervisor, she didn’t receive muchencouragement from her mostly male peers. “Theold foresters were like, Why don’t you just study
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growth and yield?” Simard told me. “I was moreinterested in how these plants interact. They thoughtit was all very girlie.”
Now a professor of forest ecology at the University ofBritish Columbia, Simard, who is 60, has studiedwebs of root and fungi in the Arctic, temperate andcoastal forests of North America for nearly threedecades. Her initial inklings about the importance of
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mycorrhizal networks were prescient, inspiring wholenew lines of research that ultimately overturnedlongstanding misconceptions about forestecosystems. By analyzing the DNA in root tips andtracing the movement of molecules throughunderground conduits, Simard has discovered thatfungal threads link nearly every tree in a forest —even trees of different species. Carbon, water,nutrients, alarm signals and hormones can pass fromtree to tree through these subterranean circuits.Resources tend to flow from the oldest and biggesttrees to the youngest and smallest. Chemical alarmsignals generated by one tree prepare nearby treesfor danger. Seedlings severed from the forest’sunderground lifelines are much more likely to diethan their networked counterparts. And if a tree is onthe brink of death, it sometimes bequeaths asubstantial share of its carbon to its neighbors.
Although Simard’s peers were skeptical andsometimes even disparaging of her early work, theynow generally regard her as one of the most rigorousand innovative scientists studying plantcommunication and behavior. David Janos, co-editorof the scientific journal Mycorrhiza, characterized herpublished research as “sophisticated, imaginative,
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cutting-edge.” Jason Hoeksema, a University ofMississippi biology professor who has studiedmycorrhizal networks, agreed: “I think she has reallypushed the field forward.” Some of Simard’s studiesnow feature in textbooks and are widely taught ingraduate-level classes on forestry and ecology. Shewas also a key inspiration for a central character inRichard Powers’s 2019 Pulitzer Prize-winning novel,“The Overstory”: the visionary botanist PatriciaWesterford. In May, Knopf will publish Simard’s ownbook, “Finding the Mother Tree,” a vivid andcompelling memoir of her lifelong quest to prove that“the forest was more than just a collection of trees.”
Since Darwin, biologists have emphasized theperspective of the individual. They have stressed theperpetual contest among discrete species, thestruggle of each organism to survive and reproducewithin a given population and, underlying it all, thesingle-minded ambitions of selfish genes. Now andthen, however, some scientists have advocated,sometimes controversially, for a greater focus oncooperation over self-interest and on the emergentproperties of living systems rather than their units.
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Suzanne Simard in Nelson, British Columbia,holding a Douglas fir seedling, right. Shestudies the way trees exchange carbon, waterand nutrients through underground networks offungus.
Before Simard and other ecologists revealed theextent and significance of mycorrhizal networks,foresters typically regarded trees as solitaryindividuals that competed for space and resourcesand were otherwise indifferent to one another.Simard and her peers have demonstrated that thisframework is far too simplistic. An old-growth forestis neither an assemblage of stoic organismstolerating one another’s presence nor a mercilessbattle royale: It’s a vast, ancient and intricate society.There is conflict in a forest, but there is alsonegotiation, reciprocity and perhaps evenselflessness. The trees, understory plants, fungi andmicrobes in a forest are so thoroughly connected,communicative and codependent that somescientists have described them as superorganisms.Recent research suggests that mycorrhizal networksalso perfuse prairies, grasslands, chaparral and Arctictundra — essentially everywhere there is life on land.
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Together, these symbiotic partners knit Earth’s soilsinto nearly contiguous living networks ofunfathomable scale and complexity. “I was taughtthat you have a tree, and it’s out there to find its ownway,” Simard told me. “It’s not how a forest works,though.”
In the summer of 2019, I met Simard in Nelson, asmall mountain town not far from where she grew upin southern British Columbia. One morning we droveup a winding road to an old-growth forest and beganto hike. The first thing I noticed was the aroma. Theair was piquant and subtly sweet, like orange peeland cloves. Above our heads, great green plumesfiltered the sunlight, which splashed generously ontothe forest floor in some places and merely speckled itin others. Gnarled roots laced the trail beneath ourfeet, diving in and out of the soil like sea serpents. Iwas so preoccupied with my own experience of theforest that it did not even occur to me to considerhow the forest might be experiencing us — untilSimard brought it up.
“I think these trees are very perceptive,” she said.“Very perceptive of who’s growing around them. I’mreally interested in whether they perceive us.” I askedher to clarify what she meant. Simard explained thattrees sense nearby plants and animals and alter theirbehavior accordingly: The gnashing mandibles of aninsect might prompt the production of chemical
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defenses, for example. Some studies have evensuggested that plant roots grow toward the sound ofrunning water and that certain flowering plantssweeten their nectar when they detect a bee’s wingbeats. “Trees perceive lots of things,” Simard said.“So why not us, too?”
I considered the possibility. We’d been walkingthrough this forest for more than an hour. Our sweatglands had been wafting pungent chemicalcompounds. Our voices and footsteps were sendingpressure waves through the air and soil. Our bodiesbrushed against trunks and displaced branches.Suddenly it seemed entirely plausible that the treeshad noticed our presence.
A little farther along the trail, we found a sunny alcovewhere we stopped to rest and chat, laying ourbackpacks against a log plush with moss and lichen.A multitude of tiny plants sprouted from the log’sgreen fleece. I asked Simard what they were. Shebent her head for a closer look, tucking her frizzyblond hair behind her ears, and called out what shesaw: queen’s cup, a kind of lily; five-leaved bramble,a type of wild raspberry; and both cedar and hemlockseedlings. As she examined the log, part of itcollapsed, revealing the decaying interior. Simard
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dug deeper with her thumbs, exposing a web ofrubbery, mustard-yellow filaments embedded in thewood.
“That’s a fungus!” she said. “That is Piloderma. It’s avery common mycorrhizal fungus” — one she hadencountered and studied many times before incircumstances exactly like these. “This mycorrhizalnetwork is actually linked up to that tree.” Shegestured toward a nearby hemlock that stood at leasta hundred feet tall. “That tree is feeding theseseedlings.”
The trees, plants, fungi and microbes in forestsare so thoroughly connected some scientistsdescribe them as superorganisms.Mycorrhizas in the soil, right, provide thenetwork.
In some of her earliest and most famous
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experiments, Simard planted mixed groups of youngDouglas fir and paper birch trees in forest plots andcovered the trees with individual plastic bags. In eachplot, she injected the bags surrounding one treespecies with radioactive carbon dioxide and the bagscovering the other species with a stable carbonisotope — a variant of carbon with an unusualnumber of neutrons. The trees absorbed the uniqueforms of carbon through their leaves. Later, shepulverized the trees and analyzed their chemistry tosee if any carbon had passed from species to speciesunderground. It had. In the summer, when the smallerDouglas fir trees were generally shaded, carbonmostly flowed from birch to fir. In the fall, whenevergreen Douglas fir was still growing anddeciduous birch was losing its leaves, the net flowreversed. As her earlier observations of failingDouglas fir had suggested, the two species appearedto depend on each other. No one had ever tracedsuch a dynamic exchange of resources throughmycorrhizal networks in the wild. In 1997, part ofSimard’s thesis was published in the prestigiousscientific journal Nature — a rare feat for someone sogreen. Nature featured her research on its cover withthe title “The Wood-Wide Web,” a moniker thateventually proliferated through the pages ofpublished studies and popular science writing alike.
In 2002, Simard secured her current professorship atthe University of British Columbia, where she
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continued to study interactions among trees,understory plants and fungi. In collaboration withstudents and colleagues around the world, she madea series of remarkable discoveries. Mycorrhizalnetworks were abundant in North America’s forests.Most trees were generalists, forming symbioses withdozens to hundreds of fungal species. In one study ofsix Douglas fir stands measuring about 10,000 squarefeet each, almost all the trees were connectedunderground by no more than three degrees ofseparation; one especially large and old tree waslinked to 47 other trees and projected to beconnected to at least 250 more; and seedlings thathad full access to the fungal network were 26percent more likely to survive than those that did not.
Depending on the species involved, mycorrhizassupplied trees and other plants with up to 40 percentof the nitrogen they received from the environmentand as much as 50 percent of the water they neededto survive. Below ground, trees traded between 10and 40 percent of the carbon stored in their roots.When Douglas fir seedlings were stripped of theirleaves and thus likely to die, they transferred stresssignals and a substantial sum of carbon to nearbyponderosa pine, which subsequently acceleratedtheir production of defensive enzymes. Simard alsofound that denuding a harvested forest of all trees,ferns, herbs and shrubs — a common forestrypractice — did not always improve the survival and
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growth of newly planted trees. In some cases, it washarmful.
When Simard started publishing her provocativestudies, some of her peers loudly disapproved. Theyquestioned her novel methodology and disputed herconclusions. Many were perplexed as to why trees ofdifferent species would help one another at their ownexpense — an extraordinary level of altruism thatseemed to contradict the core tenets of Darwinianevolution. Soon, most references to her studies wereimmediately followed by citations of publishedrebuttals. “A shadow was growing over my work,”Simard writes in her book. By searching for hints ofinterdependence in the forest floor, she hadinadvertently provoked one of the oldest and mostintense debates in biology: Is cooperation as centralto evolution as competition?
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Simard is studying whether preserving some older trees in plots that are logged will improve the healthof future saplings. Here, 60 percent of veteran trees in the foreground have been retained, whilebehind them a vast majority have been cut.
The question of whether plants possess some form ofsentience or agency has a long and fraught history.
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Although plants are obviously alive, they are rootedto the earth and mute, and they rarely move on arelatable time scale; they seem more like passiveaspects of the environment than agents within it.Western culture, in particular, often consigns plantsto a liminal space between object and organism. It isprecisely this ambiguity that makes the possibility ofplant intelligence and society so intriguing — and socontentious.
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In a 1973 book titled “The Secret Life of Plants,” thejournalists Peter Tompkins and Christopher Birdclaimed that plants had souls, emotions and musicalpreferences, that they felt pain and psychicallyabsorbed the thoughts of other creatures and thatthey could track the movement of the planets andpredict earthquakes. To make their case, the authorsindiscriminately mixed genuine scientific findingswith the observations and supposed studies ofquacks and mystics. Many scientists lambasted thebook as nonsense. Nevertheless, it became a NewYork Times best seller and inspired cartoons in TheNew Yorker and Doonesbury. Ever since, botanistshave been especially wary of anyone whose claimsabout plant behavior and communication verge tooclose to the pseudoscientific.
In most of her published studies, Simard, whoconsidered becoming a writer before she discoveredforestry, is careful to use conservative language, butwhen addressing the public, she embraces metaphorand reverie in a way that makes some scientistsuncomfortable. In a TED Talk Simard gave in 2016,she describes “a world of infinite biologicalpathways,” species that are “interdependent like yinand yang” and veteran trees that “send messages ofwisdom on to the next generation of seedlings.” Shecalls the oldest, largest and most interconnectedtrees in a forest “mother trees” — a phrase meant toevoke their capacity to nurture those around them,
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even when they aren’t literally their parents. In herbook, she compares mycorrhizal networks to thehuman brain. And she has spoken openly of herspiritual connection to forests.
Some of the scientists I interviewed worry thatSimard’s studies do not fully substantiate her boldestclaims and that the popular writing related to herwork sometimes misrepresents the true nature ofplants and forests. For example, in his internationalbest seller, “The Hidden Life of Trees,” the foresterPeter Wohlleben writes that trees optimally dividenutrients and water among themselves, that theyprobably enjoy the feeling of fungi merging with theirroots and that they even possess “maternal instincts.”
“There is value in getting the public excited about allof the amazing mechanisms by which forestecosystems might be functioning, but sometimes thespeculation goes too far,” Hoeksema said. “I think itwill be really interesting to see how muchexperimental evidence emerges to support some ofthe big ideas we have been getting excited about.”At this point other researchers have replicated mostof Simard’s major findings. It’s now well acceptedthat resources travel among trees and other plantsconnected by mycorrhizal networks. Most ecologists
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also agree that the amount of carbon exchangedamong trees is sufficient to benefit seedlings, as wellas older trees that are injured, entirely shaded orseverely stressed, but researchers still debatewhether shuttled carbon makes a meaningfuldifference to healthy adult trees. On a morefundamental level, it remains unclear exactly whyresources are exchanged among trees in the firstplace, especially when those trees are not closelyrelated.
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In their autobiographies, Charles Darwin and AlfredRussel Wallace each credited Thomas Malthus as akey inspiration for their independent formulations ofevolution by natural selection. Malthus’s 1798 essayon population helped the naturalists understand thatall living creatures were locked into a ceaselesscontest for limited natural resources. Darwin was alsoinfluenced by Adam Smith, who believed thatsocietal order and efficiency could emerge fromcompetition among inherently selfish individuals in afree market. Similarly, the planet’s dazzling diversityof species and their intricate relationships, Darwinwould show, emerged from inevitable processes ofcompetition and selection, rather than divinecraftsmanship. “Darwin’s theory of evolution bynatural selection is obviously 19th-century capitalismwrit large,” wrote the evolutionary biologist RichardLewontin.
As Darwin well knew, however, ruthless competitionwas not the only way that organisms interacted. Antsand bees died to protect their colonies. Vampire batsregurgitated blood to prevent one another fromstarving. Vervet monkeys and prairie dogs cried outto warn their peers of predators, even when doing soput them at risk. At one point Darwin worried thatsuch selflessness would be “fatal” to his theory. In
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subsequent centuries, as evolutionary biology andgenetics matured, scientists converged on aresolution to this paradox: Behavior that appeared tobe altruistic was often just another manifestation ofselfish genes — a phenomenon known as kinselection. Members of tight-knit social groupstypically share large portions of their DNA, so whenone individual sacrifices for another, it is stillindirectly spreading its own genes.
Kin selection cannot account for the apparentinterspecies selflessness of trees, however — apractice that verges on socialism. Some scientistshave proposed a familiar alternative explanation:Perhaps what appears to be generosity among treesis actually selfish manipulation by fungi. Descriptionsof Simard’s work sometimes give the impression thatmycorrhizal networks are inert conduits that existprimarily for the mutual benefit of trees, but thethousands of species of fungi that link trees are livingcreatures with their own drives and needs. If a plantrelinquishes carbon to fungi on its roots, why wouldthose fungi passively transmit the carbon to anotherplant rather than using it for their own purposes?Maybe they don’t. Perhaps the fungi exert somecontrol: What looks like one tree donating food toanother may be a result of fungi redistributingaccumulated resources to promote themselves andtheir favorite partners.
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“Where some scientists see a big cooperativecollective, I see reciprocal exploitation,” said TobyKiers, a professor of evolutionary biology at VrijeUniversiteit Amsterdam. “Both parties may benefit,but they also constantly struggle to maximize theirindividual payoff.” Kiers is one of several scientistswhose recent studies have found that plants andsymbiotic fungi reward and punish each other withwhat are essentially trade deals and embargoes, andthat mycorrhizal networks can increase conflictamong plants. In some experiments, fungi havewithheld nutrients from stingy plants andstrategically diverted phosphorous to resource-poorareas where they can demand high fees fromdesperate plants.
Several of the ecologists I interviewed agreed thatregardless of why and how resources and chemicalsignals move among the various members of aforest’s symbiotic webs, the result is still the same:What one tree produces can feed, inform orrejuvenate another. Such reciprocity does notnecessitate universal harmony, but it does underminethe dogma of individualism and temper the view ofcompetition as the primary engine of evolution.
The most radical interpretation of Simard’s findings is
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that a forest behaves “as though it’s a singleorganism,” as she says in her TED Talk. Someresearchers have proposed that cooperation withinor among species can evolve if it helps onepopulation outcompete another — an altruistic forestcommunity outlasting a selfish one, for example. Thetheory remains unpopular with most biologists, whoregard natural selection above the level of theindividual to be evolutionarily unstable andexceedingly rare. Recently, however, inspired byresearch on microbiomes, some scientists haveargued that the traditional concept of an individualorganism needs rethinking and that multicellularcreatures and their symbiotic microbes should beregarded as cohesive units of natural selection. Evenif the same exact set of microbial associates is notpassed vertically from generation to generation, thefunctional relationships between an animal or plantspecies and its entourage of microorganisms persist— much like the mycorrhizal networks in an old-growth forest. Humans are not the only species thatinherits the infrastructure of past communities.
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Western larches being commercially grown in Procter, British Columbia.
The emerging understanding of trees as social creatures has
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urgent implications for how we manage forests.
Humans have relied on forests for food, medicineand building materials for many thousands of years.Forests have likewise provided sustenance andshelter for countless species over the eons. But theyare important for more profound reasons too. Forests
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function as some of the planet’s vital organs. Thecolonization of land by plants between 425 and 600million years ago, and the eventual spread of forests,helped create a breathable atmosphere with the highlevel of oxygen we continue to enjoy today. Forestssuffuse the air with water vapor, fungal spores andchemical compounds that seed clouds, cooling Earthby reflecting sunlight and providing much-neededprecipitation to inland areas that might otherwise dryout. Researchers estimate that, collectively, forestsstore somewhere between 400 and 1,200 gigatonsof carbon, potentially exceeding the atmosphericpool.
Crucially, a majority of this carbon resides in forestsoils, anchored by networks of symbiotic roots, fungiand microbes. Each year, the world’s forests capturemore than 24 percent of global carbon emissions,but deforestation — by destroying and removingtrees that would otherwise continue storing carbon— can substantially diminish that effect. When amature forest is burned or clear-cut, the planet losesan invaluable ecosystem and one of its most effectivesystems of climate regulation. The razing of an old-growth forest is not just the destruction ofmagnificent individual trees — it’s the collapse of anancient republic whose interspecies covenant ofreciprocation and compromise is essential for thesurvival of Earth as we’ve known it.
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One bright morning, Simard and I climbed into hertruck and drove up a forested mountain to a clearingthat had been repeatedly logged. A large tract ofbare soil surrounded us, punctuated by tree stumps,saplings and mounds of woody detritus. I askedSimard how old the trees that once stood here mighthave been. “We can actually figure that out,” shesaid, stooping beside a cleanly cut Douglas fir stump.She began to count growth rings, explaining how therelative thickness reflected changing environmentalconditions. A few minutes later, she reached theoutermost rings: “102, 103, 104!” She added a fewyears to account for very early growth. This particularDouglas fir was most likely alive in 1912, the sameyear that the Titanic sank, Oreos debuted and themayor of Tokyo gave Washington 3,020 ornamentalcherry trees.
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Mushrooms and conks are the fruiting bodies of fungi. Their underground filaments formnetworks among the root systems.
Looking at the mountains across the valley, we couldsee evidence of clearcutting throughout the pastcentury. Dirt roads snaked up and down the incline.Some parts of the slopes were thickly furred withconifers. Others were treeless meadows, sparseshrubland or naked soil strewn with the remnants ofsun-bleached trunks and branches. Viewed as awhole, the haphazardly sheared landscape called tomind a dog with mange.
When Europeans arrived on America’s shores in the1600s, forests covered one billion acres of the futureUnited States — close to half the total land area.Between 1850 and 1900, U.S. timber productionsurged to more than 35 billion board feet from five
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billion. By 1907, nearly a third of the original expanseof forest — more than 260 million acres — was gone.Exploitative practices likewise ravaged Canada’sforests throughout the 19th century. As growing citiesdrew people away from rural and agricultural areas,and lumber companies were forced to replantregions they had logged, trees began to reclaim theirformer habitats. As of 2012, the United States hadmore than 760 million forested acres. The age, healthand composition of America’s forests have changedsignificantly, however. Although forests now cover 80percent of the Northeast, for example, less than 1percent of its old-growth forest remains intact.
And though clearcutting is not as common as it oncewas, it is still practiced on about 40 percent oflogged acres in the United States and 80 percent ofthem in Canada. In a thriving forest, a lush understorycaptures huge amounts of rainwater, and dense rootnetworks enrich and stabilize the soil. Clearcuttingremoves these living sponges and disturbs the forestfloor, increasing the chances of landslides and floods,stripping the soil of nutrients and potentiallyreleasing stored carbon to the atmosphere. Whensediment falls into nearby rivers and streams, it cankill fish and other aquatic creatures and pollute
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sources of drinking water. The abrupt felling of somany trees also harms and evicts countless speciesof birds, mammals, reptiles and insects.
Simard’s research suggests there is an even morefundamental reason not to deprive a logging site ofevery single tree. The day after viewing the clear-cuts, we took a cable ferry across Kootenay Lake anddrove into the Harrop-Procter Community Forest:nearly 28,000 acres of mountainous terrainpopulated with Douglas fir, larch, cedar and hemlock.In the early 1900s, much of the forest near the lakewas burned to make way for settlements, roads andmining operations. Today the land is managed by alocal co-op that practices ecologically informedforestry.
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The road up the mountain was rough, dusty andlittered with obstacles. “Hold on to your nips andyour nuts!” Simard said as she maneuvered her truckout of a ditch and over a series of large branches thatjostled us in our seats. Eventually she parked beside asteep slope, climbed out of the driver’s seat andbegan to skitter her way across a seemingly endlessjumble of pine needles, stumps and splinteredtrunks. Simard was so quick and nimble that I hadtrouble keeping up until we traversed the bulk of thedebris and entered a clearing. Most of the groundwas barren and brown. Here and there, however, themast of a century-old Douglas fir rose 150 feet intothe air and unfurled its green banners. A line of bluepaint ringed the trunk of every tree still standing.Simard explained that at her behest, Erik Leslie, theHarrop-Procter Forest Manager, marked the oldest,largest and healthiest trees on this site forpreservation before it was logged.
When a seed germinates in an old-growth forest, it
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immediately taps into an extensive undergroundcommunity of interspecies partnerships. Uniformplantations of young trees planted after a clear-cutare bereft of ancient roots and their symbiotic fungi.The trees in these surrogate forests are much morevulnerable to disease and death because, despiteone another’s company, they have been orphaned.Simard thinks that retaining some mother trees,which have the most robust and diverse mycorrhizalnetworks, will substantially improve the health andsurvival of future seedlings — both those planted byforesters and those that germinate on their own.
For the last several years, Simard has been workingwith scientists, North American timber companiesand several of the First Nations to test this idea. Shecalls the ongoing experiment the Mother TreeProject. In 27 stands spread across nine differentclimatic regions in British Columbia, Simard and hercollaborators have been comparing traditional clear-cuts with harvested areas that preserve varying ratiosof veteran trees: 60 percent, 30 percent or as low as10 percent — only around eight trees per acre. Shedirected my attention across Kootenay Lake to theopposing mountains, where there were several moreexperimental plots. Although they were sparselyvegetated, there was an order to the depilation. Itlooked as though a giant had meticulously pluckedout particular trees one by one.
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Since at least the late 1800s, North Americanforesters have devised and tested dozens ofalternatives to standard clearcutting: strip cutting(removing only narrow bands of trees), shelterwoodcutting (a multistage process that allows desirableseedlings to establish before most overstory treesare harvested) and the seed-tree method (leavingbehind some adult trees to provide future seed), toname a few. These approaches are used throughoutCanada and the United States for a variety ofecological reasons, often for the sake of wildlife, butmycorrhizal networks have rarely if ever factored intothe reasoning.
Sm’hayetsk Teresa Ryan, a forest ecologist ofTsimshian heritage who completed her graduatestudies with Simard, explained that research onmycorrhizal networks, and the forestry practices thatfollow from it, mirror aboriginal insights andtraditions — knowledge that European settlers oftendismissed or ignored. “Everything is connected,absolutely everything,” she said. “There are manyaboriginal groups that will tell you stories about howall the species in the forests are connected, andmany will talk about below-ground networks.”
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Dusky fork moss, left. Powderhorn lichen nearKokanee Glacier Provincial Park in BritishColumbia, right.
Ryan told me about the 230,000-acre MenomineeForest in northeastern Wisconsin, which has beensustainably harvested for more than 150 years.Sustainability, the Menominee believe, means“thinking in terms of whole systems, with all theirinterconnections, consequences and feedbackloops.” They maintain a large, old and diversegrowing stock, prioritizing the removal of low-qualityand ailing trees over more vigorous ones andallowing trees to age 200 years or more — so theybecome what Simard might call grandmothers.Ecology, not economics, guides the management ofthe Menominee Forest, but it is still highly profitable.Since 1854, more than 2.3 billion board feet havebeen harvested — nearly twice the volume of theentire forest — yet there is now more standing
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timber than when logging began. “To many, ourforest may seem pristine and untouched,” theMenominee wrote in one report. “In reality, it is oneof the most intensively managed tracts of forest inthe Lake States.”
On a mid-June afternoon, Simard and I drove 20minutes outside Nelson to a bowl-shaped valleybeneath the Selkirk Mountains, which houses anactive ski resort in winter. We met one of herstudents and his friend, assembled some supplies —shovels, water bottles, bear spray — and startedhiking up the scrubby slope toward a population ofsubalpine conifers. The goal was to characterizemycorrhizas on the roots of whitebark pine, anendangered species that feeds and houses numerouscreatures, including grizzly bears, Clark’s nutcrackerand Douglas squirrels.
About an hour into our hike, we found one: small andbright-leaved with an ashen trunk. Simard and herassistants knelt by its base and began using shovelsand knives to expose its roots. The work was slow,tiring and messy. Mosquitoes and gnats relentlesslyswarmed our limbs and necks. I craned over theirshoulders, trying to get a better look, but for a longtime there was not much to see. As the workprogressed, however, the roots became darker, finerand more fragile. Suddenly Simard uncovered agossamer web of tiny white threads embedded in
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“Ho!” she cried out, grinning broadly. “It’s a[expletive] gold mine! Holy [expletive]!” It was themost excited I’d seen her the whole trip. “Sorry, Ishouldn’t swear,” she added in a whisper. “Professorsare not supposed to swear.”
“Is that a mycorrhiza?” I asked.
“It’s a mycorrhizal network!” she answered, laughingwith delight. “So cool, heh? Here’s a mycorrhizal tipfor sure.”
She handed me a thin strip of root the length of apencil from which sprouted numerous rootlets stillwoolly with dirt. The rootlets branched into eventhinner filaments. As I strained to see the fine details,I realized that the very tips of the smallest fiberslooked as though they’d been capped with bits ofwax. Those gummy white nodules, Simard explained,were mycorrhizal fungi that had colonized the pine’sroots. They were the hubs from which root andfungus cast their intertwined cables through the soil,opening channels for trade and communication,linking individual trees into federations. This was thevery fabric of the forest — the foundation of some ofthe most populous and complex societies on Earth.
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Trees have always been symbols of connection. InMesoamerican mythology, an immense tree grows atthe center of the universe, stretching its roots into theunderworld and cradling earth and heaven in its trunkand branches. Norse cosmology features a similartree called Yggdrasil. A popular Japanese Noh dramatells of wedded pines that are eternally bondeddespite being separated by a great distance. Evenbefore Darwin, naturalists used treelike diagrams torepresent the lineages of different species. Yet formost of recorded history, living trees kept anastonishing secret: Their celebrated connectivity wasmore than metaphor — it had a material reality. As Iknelt beneath that whitebark pine, staring at its roottips, it occurred to me that my whole life I had neverreally understood what a tree was. At best I’d beenaware of just one half of a creature that appeared tobe self-contained but was in fact legion — a chimeraof bewildering proportions.
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We, too, are composite creatures.
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Diverse microbial communities inhabit our bodies,modulating our immune systems and helping usdigest certain foods. The energy-producingorganelles in our cells known as mitochondria wereonce free-swimming bacteria that were subsumedearly in the evolution of multicellular life. Through aprocess called horizontal gene transfer, fungi, plantsand animals — including humans — have
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continuously exchanged DNA with bacteria andviruses. From its skin, fur or bark right down to itsgenome, any multicellular creature is an amalgam ofother life-forms. Wherever living things emerge, theyfind one another, mingle and meld.
Five hundred million years ago, as both plants andfungi continued oozing out of the sea and onto land,they encountered wide expanses of barren rock andimpoverished soil. Plants could spin sunlight intosugar for energy, but they had trouble extractingmineral nutrients from the earth. Fungi were in theopposite predicament. Had they remained separate,their early attempts at colonization might havefaltered or failed. Instead, these two castaways —members of entirely different kingdoms of life —formed an intimate partnership. Together theyspread across the continents, transformed rock intorich soil and filled the atmosphere with oxygen.
Eventually, different types of plants and fungievolved more specialized symbioses. Forestsexpanded and diversified, both above- and belowground. What one tree produced was no longerconfined to itself and its symbiotic partners. Shuttledthrough buried networks of root and fungus, thewater, food and information in a forest begantraveling greater distances and in more complexpatterns than ever before. Over the eons, throughthe compounded effects of symbiosis and
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coevolution, forests developed a kind of circulatorysystem. Trees and fungi were once small,unacquainted ocean expats, still slick with seawater,searching for new opportunities. Together, theybecame a collective life form of unprecedentedmight and magnanimity.
After a few hours of digging up roots and collectingsamples, we began to hike back down the valley. Inthe distance, the granite peaks of the Selkirksbristled with clusters of conifers. A breeze flung thescent of pine toward us. To our right, a furtive squirrelburied something in the dirt and dashed off. Like aseed waiting for the right conditions, a passage from“The Overstory” suddenly sprouted in myconsciousness: “There are no individuals. There aren’teven separate species. Everything in the forest is theforest.”
Ferris Jabr is a contributing writer for the magazine. His previous cover story on theevolution of beauty is featured in the latest edition of “The Best American Scienceand Nature Writing.” He is currently working on his first book, which explores howliving creatures have continually transformed Earth throughout its history.
Brendan George Ko is a visual storyteller based in Toronto and Maui who works inphotography, video and installation. His first art book, “Moemoea,” about traditionalvoyaging in the Pacific, will be published next year by Conveyor Editions.
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