How many trees does it take to save the planet?
It depends on who you ask. In 2019, a team of researchers led by Francois-Jean Bastin at Thomas Crowther’s lab at ETH Zurich published a paper in Science with a dramatic prospectus for solving the climate crisis. Their model of Earth’s tree carrying capacity found that the earth could support an additional billion hectares of forest land — land for trees that could, in turn, store 205 gigatons of carbon. This was equivalent, they claimed, to two-thirds of all of industrial civilization’s emissions impact. The paper framed this possibility as a fragile, time-sensitive balance: If we let emissions continue under a “business as usual” regime, we could lose hundreds of millions of hectares of potential forest lands, and therefore their carbon storage potential as well. The trees could save us — but we had to act to save them now, or at very least help them replenish their numbers.
The conclusion was clear: In order to reduce the carbon dioxide concentration in the atmosphere to safe, pre-industrial levels and forestall catastrophic global warming, we as a species needed to plant a trillion trees and harness their natural capacity for carbon sequestration. It was, in the words of the paper’s abstract, “our most effective climate change solution to date.”
Of course, the idea of planting trees to solve the overlapping ecological crises of the modern era dates further back than 2018. In 2011, the International Union for Conservation of Nature (IUCN) launched the Bonn Challenge, an effort to restore 350 million hectares of the world’s deforested lands by 2050. Even before this, organizations like the Green Belt Movement, founded by Kenyan Nobel Laureate Wangari Maathai in 1977, have planted tens of millions of trees in the name of climate mitigation, soil preservation, and ecosystem restoration.
Also in 1977, theoretical physicist and professional ideas-haver Freeman Dyson even sketched out a proposal for mass tree planting with findings eerily similar to Bastin et al. In his paper, Dyson sketched out a series of estimates on how carbon dioxide emissions could “theoretically be controlled by growing trees,” naming specifically that planting 7 million square kilometers of fast-growing American sycamore could do the job of offsetting all of our emissions. While Dyson’s intellectual attentions wandered over the next few decades, to topics like space colonies and escaping the heat death of the universe, he kept to his faith in the potency of trees (and especially genetically engineered super-trees) as climate sinks, proposing in a 2007 piece in the New York Review of Books that “If one-quarter of the world’s forests were replanted with carbon-eating varieties of the same species, the forests would be preserved as ecological resources and as habitats for wildlife, and the carbon dioxide in the atmosphere would be reduced by half in about fifty years.”
Yet none of these prior attempts to galvanize mass tree planting had quite the impact that the 2019 Science paper had. The story quickly became a cause celebre for the environmental world, cited by more than 500 news articles and untold thousands more social media posts in the first year after its publication. The next year, the World Economic Forum issued a challenge to the broader global community to meet the paper’s lofty goal, and pledges rolled in from two groups not always known for their environmental prudence: leading polluting states like China and the United States, and multinational corporations like Amazon, Shell, and Nestle.
In the wake of these grand commitments, smaller players announced that they, too, would plant as many trees as they could stand. YouTuber MrBeast, who rose to fame on the platform through a series of increasingly baroque feats of individual charity, launched a pledge to plant 20 million trees commemorating his 20 million YouTube subscribers after a meme-driven push by his fans (example post: “Petition for MrBeast to plant 20 million trees for 20 million subscribers special and single handedly save earth.”) Over the course of the last quarter of 2019, he raised more than 20 million dollars, with figures like Elon Musk, Shopify CEO Tobias Lütke, and YouTube CEO Susan Wojcicki all contributing hundreds of thousands of dollars to the cause. A score of tree planting enterprises — hastily set up businesses that claimed to convert the proceeds from your necklace purchase, in-app click, or pet photo share — arrived in 2019 and early 2020, ready to take up the charge of afforestation. These amateur, social media driven efforts were at best unprepared for the sheer magnitude of interest in afforestation, and at worst outright scams, playing on the heartstrings of young environmentalists in order to run shady e-commerce operations.
The environmental mood in the closing years of the 2010s was otherwise one of near overwhelming doom and gloom. Grim texts like science journalist David Wallace-Wells’ The Uninhabitable Earth (opening line: “It’s worse, much worse, than you think”) and climate fiction novelist Nathaniel Rich’s Losing Earth dominated the discourse, and a seemingly never ending wave of natural disasters — hurricanes, forest fires, droughts, all one after another everywhere you looked — made the weight of climate catastrophe feel all that more immediate. The climate models used to inform the Intergovernmental Panel on Climate Change (IPCC)’s reports told a story of a swiftly closing window before our planetary fate was sealed. In times like those, why not search for a silver bullet solution for the climate crisis?
Tree planting was that silver bullet. On its face, it’s the perfect solution. In scope, it finds the balance between the grand and imperial scale of global climate models and the immediate and visceral human stakes of the climate crisis. As an individual act, planting a tree is more accessible and agreeable than such stark deeds as lighting yourself on fire or blowing up a pipeline, but seemingly less ineffectual than the personal consumer responsibility mantras of yesteryear: swapping out your lightbulbs, toting your canvas bags to the grocery store, cutting your shower times in half.
Tree planting also has a cleaner reputation than other schemes to alter the climate for the better. Unlike the solar geoengineering schemes advocated by figures like Nobel Laureate Paul Crutzen and failed presidential-mayoral candidate Andrew Yang, they don’t rely on untried or novel technologies with unclear long-term ramifications. Planting spruce trees seems much more predictable — or at least less dramatic — than launching sulfurous aerosols into the atmosphere.
These mass tree planting schemes are a way to mend the various schisms that have torn through the environmental movement since climate change became the issue that swallowed all others. It’s mitigation, adaptation, and restoration all at once, a move that the bright green growth eco-modernists at the Breakthrough Institute and the old school hardliners at Friends of the Earth can nod at approvingly when presented in its vaguest form. It’s a tree planting strategy that even Donald Trump can love; as Marc Benioff, one of afforestation’s biggest boosters said, “Trees are the ultimate bipartisan issue. Everyone is pro-tree.”
This universality is at the core of the mass tree planting movement. In an interview with Reuters in promotion of his lab’s paper, Thomas Crowther boasted that, unlike all the other paths to solving climate change, with their needs for systemic political change or futuristic technology, tree planting was simple and effective. It was, Crowther said, “not only our most powerful solution — it’s one that every single one of us can get involved with.”
The difficulties arise when tree planting moves from an abstract idea to a live practice, as earnest pledges and shiny infographics transform into real groves of Sitka spruce and sycamore.
Mass tree-planting schemes often reduce the rich interwoven lives of ecological communities into columns on a spreadsheet — trees planted as undifferentiated aggregates, tons of carbon removed from the atmosphere taken as foregone conclusions. Afforestation projects are embarked upon with a logic of raw optimization. As ex-Reddit CEO Yishan Wong noted when asked why he was planning to reforest 3 billion acres of forest through his company Terraformation, tree planting is “the most cost-effective per unit way” to decarbonize. When organisms as complex as trees are reduced to a sheer numbers game, as tree planting campaigns are wont to do, neither trees nor their planters benefit.
Consider dirt. The soil, and the decompositional respiration processes at constant work within it, contribute nearly as much carbon dioxide — if not more — to atmospheric concentrations as photosynthesis takes away, according to decades’ worth of emissions studies. Yet the processes of soil respiration are chaotic and hard to track accurately. If the mechanisms of photosynthesis bring to mind industrial metaphors, orderly processions of carbon dioxide and water cycled into saccharides like cogs on an assembly line, decomposition is instead a free-for-all at a junkyard, a dizzying mass of different processes and organisms taking apart the remnants of life with no semblance of order. Decomposition is the flip side of the coin to afforestation. Every tree planting project is a futile, chaotic battle against the entropic counterbalance of decomposition. One recent study focused on soil carbon dynamics in northern China found that initial soil carbon levels played an important role in determining whether a tree plantation project actually stored carbon on net. Areas with high initial soil carbon levels actually lost soil carbon as trees were planted in them, possibly due to the disturbance of soil required to plant trees industrially.
Yet even the best-planned tree planting projects run into inevitable problems with soil respiration. As climate scientist Zeke Hausfather explained in a recent New York Times editorial, a carbon removal and storage strategy based solely on tree planting is inherently temporary, “kicking the can to future generations who will have to deal with those emissions.”
The precise manner in which many mass tree planting operations function exacerbates the temporary storage problem. For a century or more, the typical way to plant trees en masse has been to do so in monospecies stands, orderly rows and columns of trees all planted at once in phalanx-like formation. It’s a mode that can be traced back to the German states in the second half of the eighteenth century, as described in the work of historian and archivist Henry Lowood in “The Calculating Forester: Quantification, Cameral Science, and the Emergence of Scientific Forestry Management in Germany” (and later used as metaphor by James C. Scott in Seeing Like a State).
In Prussia and Saxony, a model of scientific forestry developed in two steps. First, foresters and cameralists (the big data analysts of their day) developed a methodology that quantified a forest’s constant yield based on its physical and ecological characteristics. Yet even the best-studied forests still were too unpredictable for the needs of the modernizing state, and so the same forces that once merely described forests began shaping them prescriptively into the once-theoretical Normalbaum, a model of regimented forest growth that maximized both countability and constancy of timber yields.
The structure of the Normalbaum is perfect for the needs of industrial forestry, from Germany in the eighteenth and nineteenth century to British Columbia in the present day. A forest defined by human order and devoid of the distractions and complications of non-timber-producing varieties is one that is primed for extraction. Yet this very property is what makes it so flawed for use in carbon storage.
In forest ecologist Suzanne Simard’s Finding the Mother Tree, she recounts an episode from her time as a seasonal worker at a logging company in British Columbia in the 1980s. Tasked with inspecting a plantation of spruce placed over a clear-cut patch of old fir, she quickly notes that the seedlings, arranged “in garden-like rows,” were in “pathetic” shape — sickly in appearance, limited in growth, and, most importantly, disconnected from the broader ecological networks of the forest.
It is these networks precisely that help determine the success of a stand of trees. Connections between trees of different ages, as well as the mycorrhizal linkages between tree roots and fungal networks, provide nutrients and even some forms of information sharing, allowing for the development of greater resilience and longevity within forest systems.
The catch, of course, is that it is quite difficult to plant a century-old forest on the timescale of a tree planting pledge. The complex system dynamics of an old-growth forest cannot be replicated by new trees, untethered to the networks that help sustain them. At many sites, the more effective way to increase forest cover is natural regeneration — to do nothing at all except for allowing forests to regrow naturally. In contrast, as some studies have shown, tree plantations can be more harmful to carbon sequestration efforts than they are helpful. Of course, it’s harder to claim that you personally planted N million trees if you let the forest do the work for you.
To a Bezos, a Benioff, or even a MrBeast, tree starts have become yet another number to coax upwards divorced from context.
To their most prominent advocates in government and industry, though, the reductionism of mass tree planting campaigns is a key advantage rather than an unfortunate flaw. If you’re a titan of industry or a political leader with a devoted cult of personality — or something in between the two — it’s far easier to simply declare a tree planting target or a fundraising pledge than it is to get deep into the rich details of forest restoration and protection.
It’s no surprise that so many of the most prominent backers of mass afforestation are arch-capitalists — masters of the optimization games of capital and self-image that pervade the modern economy. To a Bezos, a Benioff, or even a MrBeast, tree starts have become yet another number to coax upwards divorced from context, no different from orders shipped, monthly users, or subscribers.
This logic of trees as fundamentally fungible carbon stores even extends to the decision-making choices of states. In some cases, this manifests as simple incompetence — 10 million dead saplings in the Turkish countryside, for instance. As Z Fang writes in Lausan, China’s massive afforestation efforts, though laudable in their scale, stand in stark contrast to the state’s simultaneous support of massive deforestation projects in the Amazon and Cerrado in Brazil. But not every person or entity that felt inspired to plant a tree after reading about how they can save the planet is a relentless optimizer.
The hope and capital invested in tree planting campaigns makes sense, or at least made sense at first. The topline findings of the Crowther Lab’s paper were genuinely transformative, or at least seemed as such before the arrival of a wave of corrections, responses, and further studies that cast significant doubt on the exact magnitude and feasibility of the paper’s planting recommendations.
If the science and practice of afforestation increasingly complicates the idea that tree planting is a silver bullet for the climate crisis, then why do so many of us still want to believe?
The problem with tree planting campaigns is not that people run scams off of their promise. Barring a complete move towards an extremely ethical form of eco-socialist production, it’s hard to imagine a solution to the climate crisis that does not involve ample opportunity for some varieties of profiteering. The striking thing about the wave of mass tree planting initiatives is not that there are scams run off it but that the core of its appeal is that it feels almost scam-like, one weird trick to solve climate change that bypasses all of the messy trade-offs and fiddly pieces of emissions math that every other possible way out holds.
Prior critiques of mass tree planting programs have largely focused on their efficacy — pointing out instances in which saplings planted amidst great fanfare have wilted ignominiously months later, or poking holes in the faulty assumptions of a given carbon storage projection. These are noble endeavors, but they do not strike at the heart of what makes tree planting crazes so frustrating. MrBeast and Donald Trump (and their fans) did not endorse mass afforestation on the strength of exquisitely error-tested scientific models; a rigorous fisking of those models will not dislodge them from their beliefs.
Understanding the roots (sorry) of the appeal of mass tree planting must go beyond mere explanations of the science of afforestation. We must instead understand the more sentimental appeal of trees — the thing that makes us want to protect them and make them our saviors all at once.
Just as a few large and majestic animal species dominate headlines around ecological issues like habitat protection, poaching bans, and de-extinction — the so-called “charismatic megafauna” like lions, wooly mammoths, and whales — so do trees receive activist attention in ways that smaller plants fail to. Call them charismatic megaflora. Trees overawe us with their scope both physically and temporally — recall the concern paid toward the General Sherman sequoia, 275 feet tall and 2500 years old, as wildfires burned through central California in 2021.
The emotional appeal of trees is not just a simple matter of scale, though. Our mental landscape is shot through with arboreal metaphors, from simple family trees to grandiose trees of life. Trees crop up in folklore from Tanzania to China to Mesoamerica. Some of these mythological trees were said to support the heavens; others granted humanity wisdom or protection in our legendary past. In more modern times, the work of pioneering conservationists like John Muir further built the cultural aura that surrounds trees — he describes the giant sequoias of California as “the greatest light in the woods, in the world”: more deities than natural peers. The smaller shrubs and soil decomposers of the forest get no such shine.
These romantic notions of the forest may seem harmless, or even salutary — how many good deeds in the name of the environment can be traced back to the fond memory of a particular tree? Yet that very same romanticism can cloud our judgments, doing inadvertent harm to ecosystems and the people who live among them.
It is in the deserts of the world that this harm is most obviously felt. While the term “desert” may bring to mind desolation, deserts in practice are rich ecosystems, as full of life as any other. As geographer Diana K. Davis notes in her book The Arid Lands, our modern conception of desertification as a threat to ecosystems is a faulty notion, devised by Western imperial powers in the twentieth century to attempt to understand ecosystems beyond Europe. In deserts from the Sahara to the Gobi, states have attempted to plant forests as bulwarks against the specter of desertification. In many cases, they have done nothing but cause the problem they promised to protect against, turning biodiverse arid regions into so-called “green deserts,” areas with plenty of (monospecies) tree stands but little in the way of biodiversity or ecosystem services.
These negative ecosystem impacts can spill over into affecting the people who live in them as well. In Israel, a 70-year campaign of afforestation largely conducted by the Jewish National Fund (JNF) has succeeded in “making the desert bloom” — a dream based on the notion that “nations, like trees, must be ‘organically’ rooted in the soil and that anti-Semitism was a result of the ‘unnatural" occupational structure of Jews in Eastern Europe.’ Yet the dream of Israeli settlers in turning the dusty hills of the southeast shore of the Mediterranean green was not simply brought about by the charming blue JNF donation boxes at my local synagogue — they came with human and ecological consequences. The JNF’s tree plantation method was for decades predominantly composed of monospecies stands of Aleppo pine, a non-native species that has been found to decrease local biodiversity and increase pest outbreaks. The lands that the JNF has chosen to plant included those claimed by Bedouin people in the Negev Desert. Their mission, as stated in Israel, is not merely afforestation but “redeeming the land,” both from its desertified status and from Palestinian landholders who had otherwise lived on it for centuries. What good are the JNF’s tree planting efforts if they are in service to a state that has destroyed, as some have estimated, one million olive trees in Palestine over the course of four decades?
All of this is not to dismiss tree planting efforts on the whole as inherently flawed or in service of more nefarious goals. Efforts to plant trees, and especially efforts to help forests restore themselves, cannot be left out of any serious solution to the wicked problems of ecological degradation and climate change. Yet the status quo of tree planting efforts, haunted by the demons of relentless quantification and hopeless romanticism, cannot stand.
Accepting that trees cannot save us from climate doom does not mean abandoning the hope of ecological restoration or giving in to despair. It simply means rejecting the prospect of any one trick getting us out of the problems that centuries of greed and mismanagement have wrought. The logics of rote profit optimization and manifest destiny that helped usher in the climate crisis cannot free us from it. Neither can idealized notions of trees, divorced from both science and the particular context of land and people that each tree is planted into.
Accepting that trees cannot save us from climate doom does not mean abandoning the hope of ecological restoration or giving in to despair.
Instead of a silver bullet, trees must be just one part of a broader vision of ecological response to climate change, a vision that begins growing from the ground up rather than the god’s-eye view of mass tree planting initiatives. The trees alone may not be able to save us, but we can learn from the ways that forests grow strong when allowed to develop under their own control. Our climate futures must not be seen as straight-line paths or single-minded agendas, just as our forests should not be planted as rigid grids or monospecies stands. Instead, let our futures thrive as the messy interconnected webs of life that have proven so resilient among both humans and trees.
Jacob Sujin Kuppermann (they/them) is a writer, editor, and environmental scientist based on the Pacific coast of the North American continent. Their interests as a writer include climate change, evolutionary & ecological biology, and pop music.