MONTREAL—Marc Garneau lifted off from Cape Canaveral on the Challenger shuttle in October 1984, becoming the first Canadian astronaut in space. Because the orbital inclination of the 13th shuttle mission repeatedly placed him over Canada during his eight days aloft, again and again he found himself looking down on his native country—and most of what he saw was trees, trees, trees.      

“Whenever I wasn’t busy, I pressed my nose against the window, looking at Canada and seeing that huge arboreal forest that is our country,” Garneau, now a member of Parliament from the Montreal area, said in an interview. “You grow up in Canada learning that our country is a vast, mostly empty place, full of lakes, ice and snow—and trees. And so from space I only reinforced the idea that this is a country of trees.”

Now that country of trees—the nation whose symbol is the maple leaf and whose maple syrup is prized around the globe—is engaged in an ambitious project: a commitment to plant 2 billion more trees this decade as part of its effort to fight climate change.

This summer, Prime Minister Justin Trudeau, who made the challenge part of his Liberal Party’s election platform, traveled 300 miles northwest of the capital city of Ottawa to get down on his knees and plant the 10 millionth new tree in Sudbury, Ontario, a one-time nickel-mining center. “Planting trees is not about planting seedlings,” he said that day. “It’s about planting hope, it’s about planting a future.”

If the country meets its 2 billion tree goal, projections suggest, it could reduce greenhouse gas emissions by the equivalent of 12 megatons of carbon dioxide. The government says that would amount to taking more than 2 million gasoline-powered automobiles off the road each year. What is more, it might help counter the die-off of trees in some North American regions as a result of climate change, insect infestations and diseases.

But the effort is lagging. Two years in, Canada has planted 40 million trees, an impressive figure on the surface. But that means it still has 1,999,960,000 tree plantings to go, or 99.9 percent of the distance. And scientists and environmentalists are asking whether tree-planting in the Americas should be a major policy focus, given the potential threat to water supplies in some locales, the possibility of more wildfires and the effects on food security and on biodiversity.

Critics also worry that a supply-chain problem of an entirely different sort—whether the flow of money will coincide with various elements of the planting and growing season—could stymie the effort. Some say that the government’s financial support is insufficient, and planters report that funds are not being released at the proper time in the growing season. 

Naturalists argue that to assure longevity, seed harvesters will need to target a wider variety of species than those customarily provided to the forestry companies doing the planting. Executives of those companies worry about how quickly seedlings can be produced. 

Heads of nonprofits committed to the tree offensive warn meanwhile that seedlings won’t do the trick in absorbing carbon dioxide: It is mature trees, some more than 10 years old, that are needed, especially in urban areas, they note.

Then there is the fact that at $15.3 billion, Canada’s forest-products industry—which, after all, also depends on cutting down trees—accounts for more than 1 percent of the country’s real gross national product. The industry is so active a lobby in Washington that its pleas, particularly about the import duties imposed on softwood lumber, are often the leitmotif of diplomatic laments about Canadian-American trade relationships. 

In all, for as long as reliable trade statistics have been compiled, no nation has derived more net benefit from trade in forest products than Canada: It has the world’s largest forest-product trade balance, $14.9 billion. Sweden and Finland come next but are falling behind swiftly.

Reverberations of a Pipeline Project

Canada’s tree offensive grew out of an unusual mixture of controversy and coincidence. Trudeau’s decision in 2019 to support the Trans Mountain pipeline stirred both deep support and deep opposition in his country. Just as he was working to keep his Liberal Party in power in the 2019 federal election campaign, the climate activist Greta Thunburg visited Canada and was a prominent figure in climate rallies in Vancouver, Edmonton and Montreal, where she accused Trudeau, “like all politicians,” of “not doing enough.” That day his Liberal Party announced the trees initiative, saying that the costs would be subsidized by revenue from the pipeline.

Despite the disappointing start—growing seedlings takes time, Ottawa argues, and it’s not easy to mobilize seed collectors and nurseries—Canada is rallying to the challenge of increasing its annual tree planting by 40 percent, putting land that would jointly amount to about twice the size of Prince Edward Island under a carbon-trapping canopy.

Although Nature4Climate, an international coalition of conservation groups, argues that trees planted in the tropics “grow quicker and therefore can capture more carbon,” 

Canada—1,400 miles from the Tropic of Cancer—is pressing ahead. The nonprofit group Forests Ontario is three-quarters of the way toward reaching the goal of its 50 Million Tree Program. ReLeaf-Nova Scotia is working to replace the trees devastated by Hurricane Dorian in 2019. And Trees Winnipeg is involved in an effort to plant a million trees in Manitoba’s capital city over the next 20 years: the group distributes 14 different tree species, including pin cherry, Swedish aspen, dwarf Goodland apple, paper birch and silky white willow. 

“People here are very attuned to everything involving trees,” said Christopher Adams, a political scientist who is rector of St. Paul’s College at the University of Manitoba, “and for the first time it has become an issue in a Winnipeg mayoral contest.” Five of the 13 mayoral candidates in the Oct. 26 municipal election have taken a trees pledge, vowing that for every public tree lost, the city will replant at least two new ones, water them adequately and maintain a seven-year pruning cycle.

Canada is not alone in this effort. When global governmental officials, bankers, public intellectuals and journalists gathered in 2020 at the World Economic Forum in Davos, Switzerland, they adopted an initiative to plant 1 trillion trees by 2030 that was even embraced by President Donald J. Trump, an avowed climate-change skeptic. The same year, Ethiopians planted more than 353 million trees in a half-day. Australia and New Zealand each pledged to plant a billion trees. 

China has vowed to fill 87 million acres, amounting roughly to the size of Germany, with newly planted trees to create a “Great Green Wall” by 2050. Ireland has pledged to cover almost a fifth of the country with forests by the middle of the century. And countries such as Colombia, Pakistan and Fiji have undertaken tree-planting offensives. 

Despite the enduring obstacles to mounting a concerted global offensive against climate change, a bandwagon effect has evidently materialized on the tree-planting front. Within months of the World Economic Forum’s Davos declaration, the first national chapter of 1t.org, dedicated to reaching the 1 trillion trees goal, was launched in the United States. And the U.S.-based Eden Reforestation Projects has planted 977 million trees at 280 sites in 10 countries. 

New York City has planted 13,000 trees in the last year alone and expects to plant 20,000 annually in years to come. The Arbor Day Foundation is marking the 150th anniversary of that annual April observance by pledging to plant one tree for every Instagram, Twitter or Facebook post with the hashtag #ArborDay, up to 75,000 trees, and the paper-product industry powerhouse Kimberly-Clark is matching the effort. A #TeamTrees campaign supported by the YouTube personality MrBeast had planted 20.7 million trees around the world by the end of August. The Nature Conservancy’s Plant a Billion Trees campaign hopes to plant a billion trees across the planet.

All this at a time when, according to Stuart L. Pimm, a professor of conservation ecology at Duke University’s Nicholas School of the Environment, “human actions are driving plant species to extinction at rates a hundred to a thousand times faster than normal.” Overall, about one in six trees native to the United States is in peril, threatened by tree diseases, insect infestation and climate change.

As with every other target in the battle to arrest climate change, time is a factor. “It takes a while for trees to grow—and it takes a while for them to absorb carbon dioxide,” former Secretary of State John F. Kerry, who has been President Biden’s special envoy for climate change since early 2021, said in an interview. “But it’s something we have to do.”

Scientifically, a Handy Bank for Carbon 

The science behind the tree-planting frenzy is simple. Think of trees as banks. You make a deposit into the ground, and the tree pays dividends in the atmosphere by absorbing carbon dioxide. “You can plant a tree as a child, and by the time you’re an adult, it has stored an unbelievable amount of carbon,” said Colin Laroque, director of the Mistik Askiwin Dendrochronology Laboratory. 

When a tree grows, about half of its structure consists of carbon. Over time, it adds biomass, creating a highly efficient way to store carbon quickly. Laroque explains the phenomenon by invoking a popular Canadian venue for coffee and doughnuts. “If you go through the drive-through at a Tim Horton’s to get your morning coffee, the carbon you inject into the air will take 75 years to disperse,” he said. “You can put away far more that much carbon easily in a year with a tree. And that’s just one tree.”

Katharine Hayhoe, a Canadian atmospheric scientist who holds an endowed chair in public policy and law at Texas Tech University and is the chief scientist for the Nature Conservancy, calls trees “a phenomenal technology that is exactly what we need to pull down the carbon from the atmosphere and put it into the soil where we want it.” She supports a three-step plan endorsed by Nature United, the Canadian branch of the Nature Conservancy: “We need to protect what we have, then manage our forest and, finally, then restore by planting more trees,” she said. “There’s so much we can do with nature.”

Beyond the physical, planting trees affects the emotional environment in which people live, especially in cities. Hayhoe notes that planting trees in cities in Canada and the United States would provide 1 degree Celsius of relief on summer days and filter the air, but also improve mental health. “Trees cool the local environment by providing shade canopies, especially important as our summers get hotter,” she said.

In Montreal, the city government has appropriated more than $3.9 million to ameliorate the effects of heat waves; the city recorded two days of temperatures exceeding 89 degrees Fahrenheit in August. In Phoenix, where temperatures soar far higher, the city has enlisted a landscape architect to manage the planting of trees in the city’s “heat islands,” which disproportionately affect Black and Hispanic neighborhoods.

Yet there are unanswered questions about whether the introduction of more trees will affect local water supplies, a challenge in water-thirsty Phoenix. Esteban Jobbágy, an ecologist at Argentina’s National University of San Luis, conducted a two-year study and concluded that this could be a problem.

Reforestation is in too early a stage to yield reliable examples of depleted water supplies. But a recent study in the journal Nature by a group of Dutch scholars at Wageningen University & Research suggested that a tree offensive could have wildly divergent effects, especially on water availability, which could increase by as much as 6 percent in some regions but fall by as much as 38 percent in others. Moreover, the scholars found, increased evaporation from the growth of trees could cause some rivers to lose as much one-sixth of their stream flow. 

Planting could have broader repercussions. Robin Chazden of the University of Connecticut and Pedro Brancalion of the Universidade de São Paulo warned in a 2019 article in the journal Science that reforestation programs might “threaten food and land security, and exacerbate social inequities.”

Moreover, there are worries that planting trees in areas where none existed before might decrease biodiversity “without increasing total carbon stored in above-ground biomass,” according to a study published in the journal Nature Sustainability that examined such an effort in Chile. 

The effects are a matter of continued controversy, with some scientists predicting that reforestation will diminish plant and animal diversity while increasing poverty and jeopardizing pastoral livelihoods. 

Then there is the possibility that increased tree coverage could mean increased forest fires. A 2021 study in the journal Global Change Biology suggests there are “climate-smarter options, such as wetlands restoration or recovery of grassland, that provide similar benefits for climate but also develop less flammable landscape.”

Nature4Climate, an international conservation coalition, goes so far as to say that “blanketing the Earth with trees” can be counterproductive, especially if the plantings are of nonnative or exotic species. “Planting the wrong trees in the wrong places can undermine climate, biodiversity or sustainable development goals,” the group warns. “In other instances, there are competing uses for land that are better options. And in yet others, the best and cheapest option is to let forests naturally regenerate.”  

At the same time, it is important to manage people’s expectations. Growing trees is not a one-afternoon affair, and success is not guaranteed. 

“You have to nurture trees,” said Kevin Evans, director of woodlands operations at Dartmouth College, which owns considerable forestland in New Hampshire’s North Country and uses a pine tree as its logo to cultivate its image as an institution carved out of, or into, the state’s forests. “You can’t just plant a tree and expect that right away you will draw a bunch of carbon out of the atmosphere. You’ve got to make sure these trees have space over time, and in years of drought, you need to assure there is water.”

The Dartmouth forestry team planted 6,500 trees in 2017 in the Second College Grant, a remote township of vast near-wilderness that it acquired in 1807 near the Canadian border. The effort was hampered by drought in the first years. About three-fifths of the trees survived, a success rate that Dartmouth considered a victory. “It was not an easy effort, and the goal of planting 2 billion trees is not going to be easy to pull off,” Evans said. “Getting nursery stock is difficult. There are all sorts of supply chain problems. A billion trees is a lot of trees. Two billion is really a lot.”

Deforestation, Viewed From Outer Space

“Our Canadian goal of 2 billion trees sounds like an enormous amount, but it is a small number compared to the number of trees we have in Canada,” said Garneau, the former Canadian astronaut who later became the country’s foreign minister. “Planting trees is a very good thing, but the benefit of being a carbon sink may not be as big as some people think.”

He added: ”We also have to keep those trees there—and not lose a huge amount of them due to fires, because it not only decreases the number of trees but it adds carbon to the air. All that carbon the tree was able to absorb suddenly can be released in a fire.”

That’s a danger he viewed from space while flying over Brazil in the 1980s. “I saw massive fires, deliberately set to create agricultural land in the Amazon rainforest in the state of Rondônia,” he said. “There was so much smoke, it was sometimes impossible to see large areas of Brazil below.”

It’s a worry that haunts Kerry, the 2004 Democratic presidential nominee, former secretary of state and now Biden’s climate envoy. “Having trees is important, but preventing deforestation is more important,” he said. “You just can’t have a tree strategy. You have to have so much more. The more trees you can plant the better— something people can do, kids can do it at school—but it has to be part of a much larger strategy to reduce emissions.”

Trees serve as barometers of changes in the earth. A team of four scientists reported in the journal Nature in August that the northward march of spruce trees—a migration caused by Arctic warming and decreasing sea ice—is “altering carbon cycling and further changing climate.” 

“This increasing Arctic tree cover is accelerating as a consequence of and feedback to climate changes that will shift subsistence resources available to Arctic peoples, decrease habitat for migratory species, reduce land-surface albedo and redistribute carbon stocks, all with global implications,” the scientists wrote.

A Biblical and Folkloric Resonance

Still, planting trees has a primordial appeal. After all, trees were a vital element of the Earth’s story long before climate change was an issue. The Book of Genesis recounts that on the third day of creation, God commanded that the Earth “bring forth grass, and herb yielding seed after his kind, and the tree yielding fruit.” Soon, humans were exposed to “every tree that is pleasant to the sight, and good for food; the tree of life also in the midst of the garden, and the tree of knowledge of good and evil.”

Trees have also played a major role in fables and parables across the ages, instilling an instinctive longing for their embrace. Decades before scientists sounded a warning about rising global temperatures, there was Arbor Day. It began in 1872 in Nebraska, a windswept plain devoid of trees yet a fertile area where pioneer farmers yearned for the forests they remembered from their Eastern childhoods. There as elsewhere, prairie farmers also needed windbreaks to fight soil erosion. 

By 1883, the Arbor Day notion had spread to Canada, first to Quebec and then to Charlottetown, Prince Edward Island, where people marked the occasion by planting trees on five town squares. By 1885, Ontario schoolchildren had the day off to plant trees and spruce up school grounds.

“Trees are the loudest silent figures in North American history,” said the historian Eric Rutkow, the author of the 2013 book “American Canopy: Trees, Forests, and the Making of a Nation.” “In many ways the continent has been defined by its relationship to trees. And in Canada, trees are even more important culturally than they are in the United States.”

North America was once far more forested than it is today. “When the first white man set his foot upon Canadian soil,” John L. Stoddord, a popular lecturer in American history, wrote more than a century ago, “a dense and shadowy forest, sublime in its unbroken continuity, and haunted by the solitude of unnumbered ages, rolled its billowy treetops, like a dark green ocean, from the Atlantic half across the continent.” 

Trees were an indispensable element of both the American and Canadian transcontinental railroads, which bound the countries together in roughly parallel belts of steel. 

The American railroad’s construction required the laying of 26,000 wood rail ties a day and several wood trestles and bridges; the Central Pacific engine that pulled into Promontory Point, Utah, in 1869 to complete the railway was powered by wood. 

As early as 1827, stones quarried in Hog’s Back, Ontario, for the construction of the Rideau Canal traveled to the work site on wooden rails, and when Canada embarked on its transcontinental railway in 1880, it depended on wood for bridges and ties. The Stoney Creek bridge in southeastern British Columbia was the highest timber trestle ever built.

On either side of the border, there remains something spiritual about planting a tree.

The Nova Scotia-based climate writer Marq de Villiers captured the folk memories and cultural power of trees in the recently published book “The Longbow, the Schooner and the Violin: Wood and Human Achievement.” 

“In almost every culture where forests exist,” he wrote, “they have been places of hidden ritual, home to totemic creatures, impenetrable gloves holding bottomless waterholes, sacred stones, cave labyrinths, keys to the mysteries.” 

And as so many know, Robert Frost’s woods were lovely, dark and deep. Perhaps the current tree-planting campaigns are one of humankind’s promises to keep.