Daniel Lewis is the Dibner senior curator for the history of science and technology at the Huntington Library, Art Museum and Botanical Gardens in Los Angeles.
This essay is adapted from his forthcoming book, “Twelve Trees: The Deep Roots of Our Future.”
The big coast redwoods (Sequoia sempervirens) are magnificent, like news from another world. A few individuals grow to just shy of 400 feet, making them the tallest carbon-bearing organisms on Earth. We still don’t know why they get so high, nor why they’re not even taller. But their sheer bigness — their height, their circumference, their massive bulk, their huge payloads of tissue and carbon and ancient wood — relocates us. If we pay attention, they can lead us to our better selves. They can confront us with our frailties, our smallness and our puny life spans, while reassuring us that life can go on, and that if we are part of the living world, we too can go on. I find it reassuring that an entity this extraordinary can live while we live in a sliver of shared time.
There’s something congregational about the redwoods in their groves: a group of worshippers, petitioners standing solemnly, upright before an even higher power than themselves; the calculus of wind, rain, sun, oxygen, carbon dioxide and time. Standing among the coast redwoods creates a sense of wonderment, delight and, ultimately, the knowledge of the tree’s right to exist, to not have to serve as a means to human ends. Awe isn’t the exclusive property of tourists, monks and rubberneckers. Scientists are driven not only by intellectual pursuits but also by astonishment — and by its cousin, desire. To claim that science is impartial and bloodless is incorrect.
There are only three redwood species in the world, despite a fossil record littered with others from the dim past. One survivor is the dawn redwood, which is native to just one valley in south-central China, although it plants well around the world. The other is the coast redwood’s cousin, the giant sequoia, Sequoiadendron giganteum, another huge tree often mistaken for the coast redwood despite no overlap in their ranges and different biology. The coast redwood lives almost exclusively along the upper California coast in a maritime climate, though a few, wantonly ignoring state lines, have pushed up into Oregon and down to Southern California.
A mature redwood adds, on average, a ton of wood to its mass every year. It can be up to 25 feet in diameter near the ground. Explorers in the 1840s immediately logged the trees extensively; by most reliable accounts, there were about 2 million acres in existence when first “discovered.” More than 96% of the tree’s earlier acreage was lumbered down to about 90,000 old-growth individuals. Most of these giant conifers are now within areas protected by the state or the federal government, sheltering in place against the multifarious threats of the outside world.
The constrained boundaries of the redwood population and the trees’ proximity to roads mean that it’s easy to encounter whole groves in person. Our eyes are accustomed to being able to take in the extent of a tree, to make sense of its tree-ness. But when I saw a redwood for the first time, it struck me that the trees were more like massive, notched slabs of rock. They’re unmoving under your hands; they are striated and rough and stretch off to both sides, more akin to a wall than a tree. People climb them and speak of their heights with wide-eyed reverence. You crane your head up and can’t see the top. Mossy ledges higher up on the trees look for all the world like ledges on a rock face, with other species of trees growing on flattened protuberances.
The coast redwood holds up the sky. And what holds up the tree? Soil, and lots of it. The alluvium from which the trees grow — clay, sand and silt, the remainder of long-gone riverbeds — is some 20 feet deep in places. The root system of the tree spreads roots laterally for ridiculous distances — nearly 100 feet, although in a relatively shallow fashion. The redwood’s bigness means it takes up a lot of ecological real estate. There are soil, air, water and chemical dramas. There are pollinators, incubators, microbes, contributors, givers, takers. All are actors in a production that stretches from the tips of the coast redwood’s roots to the tops of its canopies and then radiates out from there to the bigger world: the forests the tree makes.
Every species of tree is unique, but with the coast redwood, oddities and contradictions proliferate. It’s what botanists call a late-successional species or a climax species: Having survived for a long time, it’s reached a state of equilibrium and is as ecologically stable as can be. But at the same time, it’s also adaptable to disturbance.
Those two aspects of trees are usually mutually exclusive. And then there are the oxymoronic white redwoods. There are about 400 known albino trees, white drops in a big lake of green. They’re usually small, often no more than shrubs, although they can rise to about 30 feet. Due to a mutation, their needles can’t produce the chlorophyll that gives trees their green raiment. But nature provides, and the tree can draw its energy from a photosynthesizing mother plant, or through higher stomatal conductance: the process of cycling CO2 and water vapor through the stomata, or tiny pores that plants require to undertake the tree equivalent of breathing. These albinos are found across the tree’s range, and their albinism is a useful trait that allows geneticists to study mutation rates and the trees’ relationships with water and light.
There are also 10 known individual trees in the wild that contain more than one genotype, and are thus both albino and not albino, with green and white foliage interspersed. These chimeras have a chlorophyll deficiency that gives their leaves a range of colors from white to yellow to silver. These genetic oddities are the subject of considerable research.
You would expect a tree this big to be old, and though size and age aren’t necessarily correlated with trees, they are with this one. Long lives are inscribed all over the coast redwood. Big is beautiful, as is living long, but it’s also hard work. Root systems are under constant stress from the trees’ weight, and from the leveraging effects of wind and other adjacent trees. Huge boluses of bark and wood bulge out from some of the trunks. Burn marks from lightning strikes and gaping cavities are abundant. Notches from the dawn of the 20th century — evidence of wood extracted for railroad ties without cutting down the whole tree — are frequent. Even with these stresses, the oldest-known coast redwoods clock in at 2,200 years, making them some of the planet’s most ancient trees.
Every species of tree offers lessons to the world, both humanistic and scientific, and they all fill the spaces between those two often arbitrary poles. The tallest redwoods continue to grow at a rate of about a quarter inch a year. But even with abundant rainfall, the upper leaves on the tallest trees are stressed from a relative lack of water. The answers to the “Why so tall?” and “Why not taller?” questions seem to involve water, as is the case for so much about trees. Ultimately, it’s most likely a matter of hydraulics: A tree’s height appears to be limited by the enormous effort needed to lift water through tiny tubes, or xylem — the transport tissue that constitutes most of its mass.
As a rule, less water at the top of a tree means it’s harder for leaves to photosynthesize and expand. Individual trees in the drier, southern parts of the redwood’s range are shorter. But climate change will also modify the height equation in the coming decades, as higher CO2 levels, the carbon balance and changes in temperature and moisture will probably mean shorter trees. It takes a redwood weeks to pull water up from its roots to the canopy. Sucking water up a straw from a drinking glass is a trivial task. But as a straw gets longer and longer, the pressure needed to raise the water gets greater. The tree pulls mightily against the negative pressure generated by passing liquid through wood. The tallest redwoods probably generate some two million pounds of negative pressure.
The tallest of these trees is so tall that if you were tethered at the top and swaying in the breeze (while praying for your life), you’d be able to look down and see the Statue of Liberty’s bald spot, if she had one. That is, of course, if the Statue of Liberty had been relocated to a spot adjacent to Hyperion, the tallest known redwood. And moving Lady Liberty would be easier than relocating the tree, simply from a weight perspective, not to mention all those roots. Loggers weighed, segment by segment, one huge fallen redwood, the Lindsey Creek tree in Fieldbrook, California. The tree weighed 3,630 tons, more than 16 times heavier than the Statue of Liberty.
People climb far up into the high embrace of these trees, including Jerry Beranek, a pioneer of coast redwood climbing who first ascended one in 1971. As Jerry described it: “The views from the vertical column have a stunning three-dimensional effect: distance, depth and space filled in with the trunks of giant amber columns stirring and swaying.” Few people have had an opportunity to get that high up into a tree. More humans have summited Mount Everest than have gotten higher than 300 feet up a coast redwood.
In the canopy, amazing worlds emerge. Different species of trees thrive in soil up to 3 feet deep within the inner folds of some of the redwoods. One tree climber once found an 8-foot-tall Sitka spruce growing in the upper heights of a giant redwood.
Beranek described the tree and its environment as a world unto itself. He told me: “Other than a few lichen and mosses that are adapted specifically to life in the canopy, everything else — and I do mean everything — that you see growing in the redwood forest can be found growing in the canopy of our old-growth redwoods.” He’s even seen grass growing on high.
Epiphytes (plants that grow on other plants, a common strategy for botanic life around the world) build up bulk and size, drawing their moisture and nutrients from the air, rain and nearby debris. As those rafts of plant matter accumulate, they create a carpet-like layer that collects falling organic material: leaves, twigs, bird poop and other debris shaken loose by the wind or birds. This organic material starts to decay, with help from omnipresent microbes, and soil is born. Not only does the soil host other forms of life — including small creatures ranging from crickets and beetles to mollusks, amphibians and earthworms — it also regulates the climate within the canopy, providing insulation against temperature fluctuations, sound and wind.
It’s not just plant material up in the canopy. The zoologist Michael Camann has found aquatic crustaceans called copepods living in the fern mats — lush, large epiphytes that grow atop branches or inside of tree cavities. Other surprise animals have been found, including a new species of earthworm and wandering salamanders (Aneides vagrans), which spend almost all of their lives up in the canopy.
As amphibian populations around the world decline, learning their survival strategies becomes more urgent. A 2022 study described the wandering salamander’s ability to glide and parachute out of the crowns of the redwoods when disturbed. This behavior had been observed before, but the new study focused on their specific aerial maneuvers and evolutionary adaptations.
Jumping out of a tree is a risky way to escape a threat, because the salamanders have no obvious aerodynamic control mechanisms to slow their fall: no flaps, membranes, wings or other obvious speed-slowing tools. Dropping the salamanders into a wind tunnel and using high-speed cameras, researchers showed that the reptiles assume a stable skydiving posture, allowing them to maintain a steady speed and control their direction. Falling at about a meter per second, the salamanders can take up to two minutes to fall from the tops of the tallest trees to the ground. It turns out that the salamanders’ shape helps them survive this aerial enterprise: a body that’s just flattened enough, and large feet with long toes, helping to create drag and balance.
Discoveries in and among the redwoods demonstrate other survival tools of the redwood’s residents, helping to counteract the narratives of decline. A 2018 survey of nine large redwood trees yielded a total of 137 species of lichen, several new to science. One of them was Xylopsora canopeorum, its specific name celebrating the canopy in which it was discovered. The lichen seems to be unique to the warmer and drier forests in Sonoma and Santa Cruz counties — an exciting finding. As climate change affects trees everywhere, that warmer climates have fostered lichen new to science is encouraging.
The tree also has its ghosts. One of the redwood’s most mysterious residents has been the marbled murrelet (Brachyramphus marmoratus), a small endangered seabird whose secretive ways meant that its nests went undiscovered for a very long time.
The bird has long seemed to have otherworldly powers. Flying close to the ground, a murrelet is one of the fastest birds in the world; it can reach up to a hundred miles an hour, a passing blur. Eskimos called them “fogbirds” and “foglarks” because of their preference for cloudy, misty habitats — but nobody could conclusively describe their nesting habits.
One hundred and eighty-five years would pass between the German naturalist Johann Friedrich Gmelin’s assiduous but imperfect description of the bird and the discovery of the location of its home. Theories among energetic professional and amateur bird people abounded, each crazier than the last. Some were convinced the bird was a ground dweller. Others, knowing the murrelet had been seen on lakes, proposed that, somehow, it lived under the water in some kind of wet subterranean home. It began to be an embarrassment to ornithologists. In 1970, the editors of Audubon Field Notes offered up a hundred-dollar reward for the first verified and documented discovery of a nest.
For four years, concerted efforts turned up nothing. And then a wiry, strong tree trimmer named Hoyt Foster, cleaning up debris from a big winter storm in a mixed grove of redwoods and Douglas firs, nearly stepped on a baby bird in a tree he was trimming. The little bird was nesting on what looked like a patch of moss, and “it looked like a squashed-up porcupine with a beak sticking out,” he recalled. “I’d never seen anything like it.”
He wasn’t sure what to do. It was a strange and pugnacious creature, pecking repeatedly at his saw. After trying to cut around the bird, he accidentally dislodged it, and it fell, landing completely unharmed after a drop of nearly 150 feet.
Foster had inadvertently solved what one ornithologist called “one of the last great ornithological mysteries in North America.” Neither he nor anyone else ever claimed the reward.
California’s coastal fogs have provided stable moisture for millions of years, but fire has helped the tree fit more effectively into its environment. The tree’s persistence story gains a new layer at the intersection of fire and Indigenous populations, some of which have had a 22,000-year tenancy on the land.
Unlike the later Euro-Americans, who considered fire to be destructive to the tree, the Indigenous residents embraced the benefits of burning and used fire to their benefit. Fire regimes have existed among the coast redwoods for centuries. The trees have thick bark, which makes them resistant to most fires, and other traits that allow them to rebound, and even thrive, after a blaze. Native Americans burned among the redwoods for a variety of purposes, including increasing the efficiency of food gathering (less undergrowth to travel through) and reducing acorn-eating insects that flitted among the understory. The Yurok, Tolowa and Wiyot tribes revered the redwood and used its wood for buildings and canoes. The tree had a deep spiritual significance for the earliest humans to see it: living and seemingly timeless, with its own creation stories and myths.
We think of these trees as immortal because they can outlive us by so much. But despite their presence in deep time and their age-less relations with other organisms, the redwood is not impervious to destruction. Modern humans with their steel instruments have harvested millions of board feet of redwood lumber, using the wood to build entire housing developments and business districts. Trees built our nation, and the biggest coast redwoods made a lot of lumber — more than a half million board feet. All told, one could yield 33 homes, a street’s worth of residences. People have constructed sheds, docks, bookshelves, tables, caskets, roadways, flumes, egg incubators, cesspools and the pipes used in municipal water systems from Hawai‘i to Florida, out of wood from Sequoia sempervirens.
Lumber-loving humans aren’t the only complications for the trees’ lives. The Earth on which the trees rest, their silent foundation, can also subvert them. A massive earthquake, a near certainty for the trees given how long they live, can end their lives like so many matchsticks falling out of a box. The Cascadia subduction zone, running from Vancouver Island in Canada down to northernmost coastal California, lies beneath the world’s highest concentration of old-growth redwoods. Subduction, a collision of two tectonic plates, can unleash a circular motion, a catastrophe trees probably never evolved to guard against. The tree rotates and whipsaws and then, like a cook snapping a length of celery, the ground movement shears off a huge part of the tree.
Coast redwoods can also lose the fight against gravity in many other ways. The heavy mass of roots that forms a flat carpet at the surface of the ground can sink, tilting the tree. Or the tree’s taproot — the long central leader running straight down under the trunk — can die back, leaving a shallow series of roots unable to sustain the tree under the regular stresses of the local climate. Bark can slip from the trunk like loose, heavy sheets of fabric, coming off in unpredictable sizes and shapes. The trees, as Beranek noted, are “chock-full of defects: old wounds, new wounds, fire scars, splits and large open breaks.” All of these injuries give openings to organisms that contribute to the trees’ decline, hastening rotting and large cavities. Just as humans stretch and wrinkle and sag, so too with these trees.
But a fallen tree can live on, often becoming part of the forest ecosystem by sprouting up new growth or serving as host to other plants, a garden of its own. To be born is to die is to be born, as the trees engage in a quiet but pitched battle. As the stem and roots break down into mulch and duff, enough organic material assembles to support other life. Vines, ferns and other trees rise straight up.
While the more recent treacherous and relentless changes to our environment pose even greater threats than the movement of earth and water, we can find surprising oases of hope in a landscape of climate dread. The survival and growth of more heat-adapted organisms within the redwoods’ ecosystems offers one example. Another is evidence that after recent fires of unprecedented severity, 95% of the coast redwoods survived and regenerated, a much higher percentage than for other species of large trees in the fire areas studied.
Humans have also helped the tree to survive in a hotter world. In one 2016 test, researchers studying the redwood’s genetic variation collected seeds from specimens on hot, dry ridges, presumably ones that had undergone some genetic adaptation to the warmer, drier climate by dint of their survival there. They then moved the 34 seedlings grown from those seeds to a pair of test sites at the eastern, inland limit of the tree’s range, an even warmer region where no other redwoods occurred, to see whether they could take root and thrive. Many of the clones performed well at each of the test sites.
To know a tree best, it’s important to move beyond biology and to the emotions and sensations it stirs. Beauty as a branch of biology is underrated. Some of the loveliest elements in the redwoods’ ecosystems are the tiniest. The range of small, close-to-the-wood species, and their visual presentations, are exquisite.
There are the Lepraria, crusty silver-green-gray lichens named because they resemble the skin of leper patients. Beauty from pain, or beauty because of pain. Bryophytes abound: moisture-loving plants, including sporophytes of Buxbaumia piperi, shaped like a green T-Rex tooth. And the lichens! The writer Richard Preston has described the Cladonia lichens growing high up on coast redwoods as “trumpets, javelins, stalks of pinto beans, blobs of foam, cups, bones, clouds and red-capped British soldiers.” Lichens are also biologically confounding and deeply complex — shapeshifters, microbiomes that are networks as much as they are individual organisms. They start to mess with our notions of where the physical boundaries of an organism begin and end.
I find the immensity of the trees deeply comforting. Redwood groves are quiet places; there is a distinct sense of the sacred. As the writer Anne Lamott noted, “The trees are so huge that they shut you up.” Their mass dampens sound, and people in and around them tend to speak in quiet, reverent tones, as often happens when walking among giants.
And the smells! The odors of a redwood forest vary depending on the season and on what is most biologically active at the time. On cold, dark, damp winter days, there are a lot of fungi and molds at work in the forest, and the air can become acrid, funky, moldy. The smells are signaling chemicals, communication between organisms, some attracting insects to pollinate and disperse seeds.
In 1971, the University of Southern California law professor Christopher Stone, trying to roust some bored students in one of his classes, put forth the radical notion that the natural world might have legal rights. He then published a seminal article in a law journal, “Should Trees Have Standing? Toward Legal Rights for Natural Objects.” (I use the word “seminal” in its etymological sense here, as in, “from seed.”)
Stone’s article would launch a rationale putting forth the rights of the natural world. In building a careful, stepwise argument through example and precedent, Stone noted: “Increasingly, the death that occupies each human’s imagination is not his own, but that of the entire life cycle of the planet earth, to which each of us is as but a cell to a body.”
Stone’s single radical, rhetorical match lit a fire that continues to burn brightly as a way to consider not just ethical imperatives for the survival of trees but also legal ones. “There will be resistance to giving the thing ‘rights’ until it can be seen and valued for itself,” he noted, “yet, it is hard to see it and value it for itself until we can bring ourselves to give it ‘rights’ — which is almost inevitably going to sound inconceivable to a large group of people.” However, the concept continues to gain traction.
Other writers have offered different valences for the ways we speak, and thus think, about nonhuman entities. Robin Wall Kimmerer, in her book “Braiding Sweetgrass,” writes movingly and convincingly about the grammar of animacy. “To name and describe you must first see, and science polishes the gift of seeing,” she notes. But when we tell someone a tree is an it and not a who, “we absolve ourselves of moral responsibility and open the door to exploitation.” It’s much harder, she points out, to turn a chainsaw onto a “she” than onto an “it.”
The writer Elizabeth Kolbert has pointed out that for most of history, people keenly understood how much they were at the mercy of their environment, dependent on the natural world for their very survival, and rivers and mountains had the last word. But the power of law, more than issues of moral suasion, may now be the tool that finally urges us, even coerces us, as a civilized world, to take action on the idea that nature deserves to live on its own terms, not ours. Ultimately, it’s a survival strategy for humans as much as for the trees.
Humans live and die by their justifications. We need reasons for things, damn it. The issue of intelligence among nonhuman species gets our attention because we instinctively think, perhaps, that we are the only entities that have what we construe as intelligence. But nature provides many counterexamples, such as the New Caledonian crow, with its ability to make and use tools to get at food and its skill in working out sequences of tasks to feed itself.
Talking about intelligence and trees is riskier, for we’ve come to consider intelligence as relevant only to other animals with brains. Human intelligence has been used for centuries as the benchmark by which all other intelligences are measured. These “vexed hierarchies” of intelligences, as the biochemist Merlin Sheldrake calls them, are now being tempered by new understandings of what trees, and other organisms, can do in terms of cognition, making decisions and other classic markers of intelligence. Cognition — the ability to detect environmental variables — is sometimes confused with consciousness, which leads to its rejection as being present in plants. But philosophers of biology have argued convincingly that plants have consciousness as well: In the simplest sense, consciousness is an awareness of the outside world.
The collective crucible of law, biology, beauty, awe, common sense and something we can recognize as intelligence can forge humans into creatures able and willing to give trees like the redwoods their own due. We move toward a kind of newfound affinity, or at least it snags our attention, when we find clues that we’re not alone in our ability to express intelligence.
For the natural world to survive, it needs long-term empathy. The future of the planet’s health is an abstraction to almost everyone, and the longer the arc of time beyond our lifetime, the greater the abstraction. We need to find ways to extend our compassion just a bit further into the future and make it less abstract. Some philosophers now propose ethical models of intergenerational heritage, building emotional connections across generational divides: a tall order. These models offer ways to stitch together current communities with the generations that will immediately follow, and then tie those to the generations that follow those, and so on — a reference chronology that ties past to future.
Update: A previous version of this essay featured an image of a giant sequoia (Sequoiadendron giganteum), a species closely related to but not the same as the coast redwood (Sequoia sempervirens).
