Marsh insisted, “Trees are no longer what they were in our fathers’ time, an incumbrance.” They are, instead, a reservoir, the source of life, the regulators of the climate.

Marsh, a linguist and a diplomat, went on to write a groundbreaking book, “The Earth as Modified by Human Action,” first published in 1864 under the title “Man and Nature,” a nineteenth-century version of Frankopan’s “The Earth Transformed.” The Wisconsin legislature in 1867 commissioned an investigation that resulted in the publication of its “Report on the Disastrous Effects of the Destruction of Forest Trees, Now Going On So Rapidly in the State of Wisconsin.” The state then inaugurated a program of tax exemption for landowners who planted trees. In 1873, the Nebraska senator Phineas W. Hitchcock introduced the Timber Culture Act, declaring, “The object of this bill is to encourage the growth of timber, not merely for the benefit of the soil, not merely for the value of timber itself, but for its influence upon the climate.” The act, a failure, was repealed in 1891. Instead, the lasting consequence of Marsh’s “The Earth as Modified by Human Action” was Arbor Day, created by a Nebraskan named J. Sterling Morton and first celebrated on April 10, 1872.

Morton, the editor of the Nebraska City News, called for a day “set apart and consecrated for tree planting.” On that first Arbor Day, Nebraskans planted more than a million trees. The holiday soon spread, especially after Grover Cleveland appointed Morton as his Secretary of Agriculture, in 1892. The advocacy organization American Forests was founded in 1875, and, as Cohen writes, it also advanced the idea that planting a tree was an act of citizenship. This was a tradition that faltered at various times in the twentieth century but was renewed beginning in 1970 with the first Earth Day (also held in April) and with the establishment of the National Arbor Day Foundation two years later. Its many programs include Trees for America; pay a membership fee, and you get ten saplings in the mail. American Forests runs Global ReLeaf.

 

But Cohen and other critics have argued that there is little evidence that these programs do much more than greenwash bad actors. American Forests has been sponsored by both fossil fuel and timber companies. In 1996, the climate-change-denying G.O.P. encouraged Republican congressional candidates to have themselves photographed planting a tree. “10 Reasons to Plant Trees with American Forests,” printed in 2001, suggests that “planting 30 trees each year offsets the average American’s ‘carbon debt’—the amount of carbon dioxide you produce each year from your car and home.” The E.P.A., on a Web site that linked to American Forests, urged Americans to plant trees as penance: “Plant some trees and stop feeling guilty.” What with one thing and another, have you used ten thousand kilowatt-hours of electricity? The site offered indulgences: plant ten trees, one for every thousand kilowatt-hours. At the height of the corporate tree-atonement era, a New Yorker cartoon showed a queue of businessmen waiting to see a guru, with one saying to another, “It’s great! You just tell him how much pollution your company is responsible for and he tells you how many trees you have to plant to atone for it.”

The notion that clear-cutting can be counteracted by the planting of trees is a political product of the timber industry. As Cohen shows, the phrase “tree farm” was coined by a publicist at a timber company, as was the motto “Timber Is a Crop.” And the notion hasn’t died. In 2020, the World Economic Forum announced its sponsorship of an initiative called 1t, a corporate-funded plan to “conserve, restore, and grow” one trillion trees by the year 2030. At Davos in 2020, Donald Trump pledged American support. (At the time, the President mentioned that he was reading a book about the environmental movement; written by a former adviser of his, it was called “Donald J. Trump: An Environmental Hero.”)

It’s good to plant trees. No one’s arguing any different. “There’s no anti-tree lobby,” a Nature Conservancy ecologist told Science News recently. Trees are the new polar bears, the trending face of the environmental movement. But it’s not clear that planting a trillion trees is a solution. In terms of biodiversity, killing forests and planting tree farms isn’t much help; a forest is an ecosystem, and a tree farm is a monoculture. Forests absorb about sixteen billion metric tons of carbon dioxide every year, but they also emit about eight billion tons. The main study behind the 1t movement proposes that planting trees on land around the world roughly equivalent in area to the United States will trap more than two hundred billion tons of carbon. Yet a forum published in Science in 2019 expressed grave skepticism about both the science and the math behind this plan. The history is fishy, too. National tree-planting schemes have, historically, come up short. Studies across countries have found that as many as nine in ten saplings planted under these auspices die. They’re the wrong kind of tree. No one waters them. They’re planted at the wrong time of year. They have not improved forest cover. The 1t folks make a point of saying that they’re not planting trees; they’re growing them. But whether they really are remains to be seen.

In the meantime, you are asked to think differently about trees. They’re out there. They’re smart. They will outlast us. Brian Selznick’s graphic children’s novel “Big Tree” (Scholastic) tells the story of trees across tens of millions of years, through the trials of two sycamores: “Once upon a time, there were two little seeds in a very old forest. Their mama said she would give them roots and wings—roots so they’d always have a home, and wings so they would be brave enough to find it.” Selznick’s understanding of forestry, and maternal trees, borrows from the work of the Canadian ecologist Suzanne Simard. As a young scientist, Simard was the lead author of a study published in Nature, “Net Transfer of Carbon Between Ectomycorrhizal Tree Species in the Field,” in which she reported the findings of a years-long series of experiments that she conducted with seedlings. “Plants within communities can be interconnected and exchange resources through a common hyphal network, and form guilds based on their shared mycorrhizal associates,” she concluded. That is to say, plants can communicate with one another chemically, and across species, issuing warnings, for instance. Put in human terms, trees can care for one another. Simard came to call certain of these signallers “mother trees,” which both got her into hot water and made her beloved. Although subsequent research verified most of her major findings, she was for a long time chastised by scientists, an experience that was the inspiration for the trials of Patricia Westerford in Richard Powers’s intricate Pulitzer Prize-winning novel, “The Overstory,” from 2018. In the novel, Powers describes the moment of Westerford’s crucial finding, in a forest of sugar maples:

The trees under attack pump out insecticides to save their lives. That much is uncontroversial. But something else in the data makes her flesh pucker: trees a little way off, untouched by the invading swarms, ramp up their own defenses when their neighbor is attacked. Something alerts them. They get wind of the disaster, and they prepare. She controls for everything she can, and the results are always the same. Only one conclusion makes any sense: The wounded trees send out alarms that other trees smell. Her maples are signaling.

Amy Adams is slated to play Simard in an upcoming film adaptation of Simard’s memoir, “Finding the Mother Tree: Discovering the Wisdom of the Forest” (Knopf).

Simard is herself something of a maternal spirit in Katie Holten’s collection of essays, poems, and other snippets, “The Language of Trees” (Tin House), in which Holten, an Irish artist and activist, introduces a tree alphabet. Each letter is represented by the striking silhouette of a tree: Apple, Beech, Cedar, Dogwood, Elm, and so on. The book reproduces a piece of Simard’s writing: “When mother trees—the majestic hubs at the center of forest communication, protection, and sentience—die, they pass their wisdom to their kin, generation after generation, sharing the knowledge of what helps and what harms, who is friend or foe, and how to adapt and survive in an ever-changing landscape. It’s what all parents do.” That “mother,” in Holten’s abecedary, reads this way: Mulberry, Oak, Tree of heaven, Horse chestnut, Elm, Redwood.

Simard’s research has also been popularized by a German forester named Peter Wohlleben in his best-selling 2015 book (first translated into English in 2016), “The Hidden Life of Trees: What They Feel, How They Communicate.” Wohlleben’s earlier books were downers, like “The Forest: An Obituary.” “The Hidden Life of Trees” is not a downer. Forget imperialism, industrialism, and capitalism. Think feelings. A forest of trees, Wohlleben argues, is like a herd of elephants. “Like the herd, they, too, look after their own, and they help their sick and weak back up onto their feet.” Like elephants—like humans—trees have friends, and lovers, and parents and children. They have language, and they also have, he argues, a kind of sentience.

As science, the mothering, feeling tree is controversial. As literature for a political movement, it’s not bad, and, after all, nothing else has worked—not Arbor Day, not the “Report on the Disastrous Effects of the Destruction of Forest Trees, Now Going On So Rapidly,” not Global ReLeaf, not 1t. At this rate, unless humans think of something better fast, the forests, and then we who walk the Earth, two-legged, will be Dogwood, Elm, Apple, Dogwood. ♦