Thomas Crowther standing in a forest

Thomas Crowther’s work, especially on trees, has produced high-profile publications, but also criticism.


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Catchy findings have propelled this young ecologist to fame—and enraged his critics

It's been a remarkable year for ecologist Thomas Crowther—for better and worse. The 33-year-old researcher, an assistant professor at ETH Zurich in Switzerland, has co-authored six papers in Nature and Science. He's addressed members of Germany's parliament and is advising major companies and nonprofits on environmental issues. Journalists have produced hundreds of stories about his laboratory's innovative work with huge ecological data sets, including a headline-grabbing estimate, published in Science, that planting trees on hundreds of millions of hectares could dramatically slow climate change. Last month, Nature published a lengthy profile of Crowther, noting his rise "from struggling student to steward of a 30-strong team," supported by a hefty foundation grant "that should keep his lab going for 13 years."

But Crowther's rapid rise to prominence has also catalyzed a strong and sometimes personal backlash. Colleagues have called him out for what they view as preening for the press (his lab has its own public relations staff) and for publishing flashy but flawed science. Critics panned the tree-planting paper, with one calling it "shockingly bad," and last week, Science published six lengthy critiques signed by more than 50 scientists. And the Nature profile, in which Crowther appeared to belittle traditional ecological research, incited a Twitter pile-on. Some users accused Crowther of being a poster boy for white male privilege in science, with one deriding his lab as "a huge waste of money."

The attacks have left Crowther and members of his laboratory feeling bewildered, even depressed. But the attention has also reinforced their feeling that they are doing meaningful, precedent-setting, and world-changing work. "Even though this has been absolutely the worst 3 months of my career," Crowther says, "it's also been the 3 months when I've realized the dream of actually having our science be useful."

Few doubt that Crowther's efforts to generate global ecological numbers are having an impact. He's "very savvy in picking problems that are going to have answers that people are going to want to know," says ecologist Jonathan Levine of Princeton University. "There's sort of a buzz around Tom."

Crowther appears to be all limbs, tall and lanky. He sometimes dons a three-piece suit for talks but favors less formal garb in his lab: for example, a ball cap, faded T-shirt, flip-flops, and hoodie. He gesticulates energetically and often speaks in hyperbole, with a healthy dose of expletives. Everyone in his lab is the most brilliant scientist or most incredible programmer he's ever met. During one recent talk he presented "the graph that gave me the most joy in my entire career."

Crowther's accent hints at his multinational upbringing. He was born in Namibia and spent his early years in South Africa, before his family moved to the coastal town of Prestatyn, U.K. His parents are doctors and his childhood was comfortable, but dyslexia made academics hard. He became known as a troublemaker and poured his energy into sports, rising to the apex of youth tennis in the United Kingdom before, he says, a lack of focus cost him his funding. At the same time, he grew fascinated with nature, devouring documentaries narrated by naturalist David Attenborough and developing a passion for catching lizards and snakes.

Crowther enrolled at Cardiff University, but did poorly until a soil ecology professor, Hefin Jones, saw his potential and, over a beer, encouraged Crowther to try harder at science. As he had done with sports, Crowther threw himself into experiments: growing wood-decomposing fungi in petri dishes, then examining the consequences of adding fungus-eating insects to the mix.

Once, Jones recalls, Crowther insisted on submitting a paper to Ecology Letters, a prominent journal, even though Jones thought the result was trivial. The journal accepted it with few revisions. The episode proved Crowther's "willingness to actually disagree with his seniors and … argue his case," Jones says. By the time Crowther completed his Ph.D. at Cardiff in 2012, he had published in several top ecology journals.

In 2012, Crowther moved to Yale University to work with soil specialist Mark Bradford. Soon after he arrived, a German high school student, Felix Finkbeiner, emailed Crowther's roommate with a question: How many trees are on Earth? Finkbeiner was curious because he ran a nonprofit that was working with the United Nations to encourage people to plant 1 billion trees.

"Why would a scientist care?" ecologist Daniel Maynard, then a grad student at Yale, recalls thinking. But Crowther embraced the challenge of amassing the data. He began to ask tree researchers to share their numbers. Some did; others refused. Then, Crowther discovered that many governments had massive data sets of forest measurements. Soon he had 400,000 data points, enough to correlate tree density with variables such as rainfall and estimate tree numbers in places with sparse data, including much of Africa and Asia. In September 2015, Crowther and colleagues—including the once-dubious Maynard, who is now in Crowther's lab—reported in Nature that the planet is home to about 3 trillion trees.

Journalists began to call. Attenborough quoted the paper. ("The best moment of my career," Crowther says.) The Billion Tree Campaign became the Trillion Tree Campaign.

Scientists had mixed reactions. Some felt Crowther had neglected more meaningful metrics, such as species distribution and function. Robin Chazdon, a forest ecologist at the University of Connecticut in Storrs, recalls thinking: "The number of trees is just kind of a flashy way of getting attention."

People said: ‘How can you be confident enough to make claims about the whole world?’

Thomas Crowther, ETH Zurich

By the time the Nature paper appeared, Crowther had moved to the Netherlands Institute of Ecology (NIOO) in Wageningen. He says he learned two things from the experience. One was that he could pull off—and publish in a prestigious journal—a credible global analysis of a single ecological variable. "People said: ‘How can you be confident enough to make claims about the whole world?’" he recalls. “The globe is the petri dish. I understand the detail of my petri dish exactly the same as I understand the detail of the globe."

The other lesson was that relatively simple studies, when clearly communicated, could excite the media and the public. "There's loads of genius scientists way smarter than me who are not willing to communicate their science, so it doesn't get the attention it deserves," Crowther says. "Science isn't about finding absolute perfection; it's about moving the conversation forward."

Crowther applied those lessons to his next big project. This time, his spotlight was on soil, which is often overlooked yet is vital for growing food—and storing carbon. In particular, many researchers want to know how global warming might change the activity of soil microbes, which play a major role in determining how much carbon is stored or released by soil. Researchers have launched numerous experiments in which they artificially warm soil in different places and measure what happens.

As he did for tree numbers, Crowther drew on other researchers' data. He plotted the results of 49 experiments and found a trend: Warming soils lost carbon, and the more carbon a site held, the more it lost. "It's the simplest thing ever. It's just that I dared to apply the concept at a global scale," he says. "I would never have been bold enough to try, until the tree paper."

Some of Crowther's co-authors wanted to emphasize the uncertainty in the results. But Crowther prevailed with a simpler message: A 1°C rise in global temperature could cause microbes to release about 55 billion tons of soil carbon by 2050, accelerating global warming by up to 17%. The result would be, he said, like adding emissions from an additional United States to the atmosphere.

The work, published in Nature just 15 months after the 3 trillion trees paper, received extensive coverage. Crowther also received an invitation to apply for funding from DOB Ecology, a family foundation in Veessen, Netherlands. The foundation rejected Crowther's first proposal as not ambitious enough. But it liked his second pitch, which called for creating a team including programmers, remote sensing experts, modelers, and communications specialists to conduct and publicize 13 global-scale studies with practical applications. In October 2017, 1 month after Crowther joined ETH Zurich, he received a $2.7 million grant from DOB Ecology, with a promise of an additional $15 million if he meets certain targets.

Members of the Crowther lab take the stage at an event held this summer for corporate social responsibility officers, donors, and nonprofit officials in Zurich, Switzerland.


Overnight, Crowther had more money than most in his field. “I’ve never heard of an assistant professor having this degree of financial support, at least in ecology,” says Levine, who was at ETH at the time. “It’s divisive, it’s horrible. … I did freak out for a little bit,” Crowther says, adding that he was embarrassed by an ETH press release crowing about the “huge” grant. “Part of the reason I’ve had academic success is that I’ve never had stress. … Then I got into this, and I’m like: ‘Oh my God, I’m responsible for 20 people.’”

Now, 2 years later, Crowther's team of about 30 occupies a hallway of ETH's environmental sciences building. The space has the feel of a startup, with lounge furniture, espresso cups, and whiteboards strewn about. You will often find Crowther at a standing desk in an office shared with five others. He declined to occupy an office next door that was offered to him. "I get so sad and bored just sitting in a room by myself," he says. Instead, it's become a game room, equipped with a table that hosts frequent bouts of "smash," a chaotic form of table tennis that Crowther invented in which players bounce the ball off walls, the floor, their bodies, and even visiting journalists.

Crowther's penchant for games and camaraderie extends beyond the office. One Friday night, he led a lab pub crawl that lasted into the early morning. At a weekend picnic, a restless Crowther searched for the optimal angle for swinging on a rope from a tree while his labmates drank beer. "Zurich was a classy place until the Crowther lab showed up," a colleague joked.

Crowther has landed like a cannonball in Switzerland's traditionally calm academic pond. Some colleagues balked when Crowther sought to hire his own publicity team. He did it anyway. And ETH faculty have chastised him for some careless remarks to the press, says environmental scientist Nicolas Gruber, an ETH colleague. But he says Crowther's "ambition level and translating that ambition to action [has been] quite amazing."

This year alone, Crowther's lab has helped produce the first-ever global distribution maps of soil-dwelling fungal groups and of tiny worms called nematodes, both in Nature, and a global map of earthworm distribution, in this issue of Science. The results will help bolster climate and ecological models, Crowther says. His team has published other work on how climates in major cities could shift by 2050.

Some of the lab's work is more hands on. Graduate student Julia Maschler is examining how climate change might affect tree growth and wood decomposition. In another study, Crowther's playfulness comes through. He speculated that exposure to sound would make fungi grow faster. Maynard, now a lead scientist in his lab, bet it wouldn't. To settle the issue, they grew fungi in chambers rigged for sound. Crowther won.

It is the Crowther lab's tree maps, however, that keep stealing the show—and engulfing him in controversy. Ecologist Jean-François Bastin, a postdoc in the lab, led an effort to determine how much unforested land on Earth could support trees. It was prompted, in part, by a practical problem: Tropical nations have committed to establishing forests across an area larger than India by 2030, but many countries don't know how much land is actually suitable.

The researchers, including computing specialist Devin Routh, built models that drew on variables such as soil type to estimate how much land could be forested, and how much carbon dioxide those trees might suck from the atmosphere. In July, they reported in Science that new trees could grow across 900 million hectares of land, where they would absorb two-thirds of the carbon dioxide humans have added to the atmosphere in the industrial era. Tree planting, the authors wrote, is "our most effective climate change solution."

The media embraced that message. English-language outlets ran some 700 stories on the paper, according to a firm Crowther hired to promote it. Climate advocate Greta Thunberg and former Vice President Al Gore, among many others, cited the result.

But many scientists objected. One of the bluntest critics was Simon Lewis, a forest ecologist at the University of Leeds in the United Kingdom, who had previously collaborated with Crowther. "Science Magazine have lost their critical faculties," he tweeted, calling the paper "shockingly bad." In particular, Lewis faulted the carbon removal calculation, arguing that Crowther's team had overstated, by a factor of two, the proportion of human-emitted carbon that trees could absorb. "That's not how the global carbon cycle works," he wrote.

Crowther and Bastin were taken aback. The attacks "stopped all work in the lab for a week," Crowther recalls.

Last week, the conflict got a full airing in Science, which published six submissions from critics (including Lewis), together with one supportive comment and responses from Crowther's team. In addition to lambasting the July paper for miscalculating carbon storage, the critics argued it favored converting grasslands and wetlands to forests and ignored how trees might affect water supplies and temperatures. "The claim that global tree restoration is our most effective climate change solution is simply incorrect scientifically and dangerously misleading," one group wrote.

Crowther's team revised the paper abstract to recharacterize tree planting as just "one of the most effective carbon drawdown solutions" and emphasize that reducing carbon emissions is critical. But they vigorously challenged other objections. Disagreements about carbon storage calculations were not the result of errors, but different definitions of "forest" and confusion about their methods, they wrote. And they denied promoting conversion of grasslands and wetlands. "All we're showing is where trees can grow," Crowther says. "It's not got any agenda."

We cannot be that bold. We get bogged down in bureaucracy.

Julian Fox, Food and Agriculture Organization of the United Nations

Ecologist Jonathan Foley, executive director of Project Drawdown in San Francisco, California, which ranks climate solutions, says his group's analysis confirms Crowther's numbers. And Julian Fox, national forest monitoring team leader at the Food and Agriculture Organization of the United Nations in Rome, credits Crowther's team for showing that some countries have made unrealistic forestation promises, whereas others could be more ambitious. His team had launched a similar study, but it realized Crowther's team could deliver harder hitting results. "We cannot be that bold," he says. "We get bogged down in bureaucracy."

Amid the dueling, even scientists who have been critical of Crowther's work say his messaging has helped advance meaningful conversations. Chazdon says the Science paper "overinflated" the potential for carbon removal, but that Crowther is "really raising the profile of forests" in discussions of climate solutions. Although she had been wary of working with Crowther in the past, Chazdon has agreed to share some of her data with him. "He's matured," she says.

This summer, a stream of corporate social responsibility officers, wealthy donors, and nonprofit directors filed into a domed conference room on the ETH campus for a Crowther lab "launch" event. Standing before a curved backdrop depicting a forest, Crowther breezed through highlights of his work on how nature can help fight climate change. The feel was more TED Talk than data dump, and he ended his remarks with an upbeat message that drew applause. "Until recently, fighting against climate change has always been about things we've got to stop—things we shouldn't do," he said. "Now, we've got positive actions we can take."

It's a message that fits today's corporate zeitgeist. Firms are awakening to climate change threats and are eager to support solutions such as tree planting. They've embraced Crowther, recruiting him for advisory boards and consulting gigs. (Crowther says he gets no money from corporations.) But outside of conferences where scientists and corporate officers swap sustainability pledges and business cards, tree-planting projects face a tougher reality. Many planted trees don't live long enough to fight climate change, says Finkbeiner, who is now at Crowther's lab. Even when trees thrive, they are often cut too quickly to affect carbon levels.

Another problem is that forest restorers typically lack scientific expertise in augmenting soil microbial communities to sustain and optimize tree growth, says Louise Vet, a biologist at NIOO who chairs DOB Ecology's advisory council. Now that Crowther has made a splash with global papers, she and the foundation directors are pushing him to focus on site-specific research that will help DOB Ecology's 11 restoration projects succeed. "That's what I'm expecting from Tom—that he bring in some of the knowledge that can be used in practice by these partners."

Crowther is confident he can do that. He is hiring for a team, dubbed RESTOR, that will evaluate forest restoration projects throughout the tropics and help funnel donor money to well-designed efforts. "We need to go all the way there to making it happen," Crowther says. "We can't just rely on people taking our science and doing something with it."

Even as Crowther sought to put the tree paper controversy behind him, a new storm hit. Soon after the 20 September publication of the Nature profile, social media erupted. Some researchers were upset by quotes in which Crowther appeared to dismiss the value of observational and field studies. "I can say, ‘That bird is flying weirdly’—that's not science; that's what most of ecology is at the moment. It's natural history," he is quoted as saying. Collecting field data is "the simplest thing ever," he suggested. Others reacted to the story's illustrations, including a video of Crowther playing smash with three white male colleagues, which some saw as highlighting a white scientific patriarchy.

One of the harshest reactions came from Katherine Gould, a biologist at Pasadena City College and Moorpark College in California. Crowther was a "boy wonder who is funded by a rich family," Gould tweeted, referring to his lab with a profanity and calling it a waste of money. Gould's thread received some 500 retweets and 1500 likes, and sent Crowther and his lab into damage-control mode.

"It was horrendous, I was depressed," Crowther recalls. He even considered leaving academia. But he was buoyed by supportive tweets from several female lab members. "I'm a happy female PhD student supervised by an ever engaged and enthusiastic" Crowther, tweeted Iris Hordijk, who studies tree demography at ETH. "Coming from a mechanical engineering lab, I've never seen so many women scientists in one lab," tweeted Tanja Koch, who recently completed a master's degree with Crowther. "And believe me the girls love smashing game as well," she added.

Crowther himself tweeted, "Just to clarify, I truly love natural history. That's why I got into ecology. I would never intend to criticize the incredible ecologists who do amazing work …" Some of his comments had been taken out of context, he protested, but apologized for any miscommunication. The flap faded, and Gould apologized for her initial characterization of Crowther and his lab. But she continued to take Crowther to task for a "colonial and paternalistic" approach to research and his lab's lack of racial diversity.

Crowther has acknowledged that unearned privilege that comes from being a tall, charismatic, middle-class white man has likely played a role in his rapid ascent. "I've been really fortunate," he said this summer, before the Nature profile appeared. "I do believe that my privilege has made me more persuasive … whether it's writing papers or encouraging a really good postdoc to come."

Crowther also says he's "seriously worried about" the fact that his senior lab members are all men, and says he is emphasizing efforts to recruit women. He recently hired a female postdoc to join the lab's leadership, part of fulfilling a vow to fill at least four of the lab's next five positions with women.

Whether such efforts will satisfy critics remains to be seen. But the back-to-back firestorms have convinced Crowther that he might need to rethink his exuberant but informal style, which has gotten him so far so fast. And he has learned twice over a lesson that every prominent person learns sooner or later: that fame and fortune can cut both ways.