The man whose research sparked a global tree-planting frenzy has urged world leaders to end their obsession with reforestation, arguing that the practice may be doing more harm than good. Speaking at COP28 in Dubai earlier this month, ecologist Thomas Crowther said his initial findings had been misinterpreted and seized upon to support “greenwashing” initiatives, while insisting that the best way to tackle the climate crisis is to focus on the protection and restoration of existing forests.

In 2019, Crowther and his colleagues published a paper in which they suggested that planting an extra trillion trees worldwide could remove around two-thirds of the carbon that humans have pumped into the atmosphere. In the wake of the media hype generated by the study, Crowther became chief scientific advisor for the United Nations’ Trillion Trees Campaign, while also taking up an advisory role for a similar initiative launched by the World Economic Forum.

“People think the campaign is about planting a trillion trees, but it was never that,” Crowther told IFLScience. “It's not even logical to try and plant a trillion trees. It’s physically impossible,” he says. 

“But what is logical is investing in thousands of farmers and donating to thousands of indigenous populations who are protecting nature.”

Unfortunately, however, companies and governments around the world were quick to jump on the bandwagon, promising to offset their emissions by planting huge amounts of trees, yet scientists were quick to pour skepticism on the whole idea. Soon after Crowther’s study came out, a critique was published that showed how his team had massively overstated the carbon-storing potential of a trillion new trees.

This was followed by another study that highlighted two of the big drawbacks to mass tree-planting - namely, that many of these trees won’t survive, and those that do will take decades to reach their carbon-capturing potential, by which time it may be too late to make any difference. These concerns are supported by the failures of national tree-planting initiatives around the world, including a project in Turkey that saw 11 million new saplings planted, only for the majority to die within three months due to a lack of rainfall.

Another study published in 2021 found that a 50-year reforestation campaign in northern India had failed to increase the proportion of canopy cover, as young trees were often planted in poor soil or trampled or eaten by animals.

Scientists have also pointed out that it’s no good simply plonking a load of trees in the wrong spot. Even before Crowther’s trillion trees pledge hit the headlines, researchers had grown concerned that millions of hectares of natural grasslands and savannahs had been earmarked for reforestation, despite the fact that these ecosystems had been devoid of trees for millions of years.

Adding trees to these landscapes can have disastrous consequences, leading to a catastrophic loss of biodiversity as habitats are destroyed while also triggering massive wildfires. Furthermore, planting trees in bald regions can darken the Earth’s surface, thus increasing global temperatures by causing more of the sun’s radiation to be absorbed rather than reflected.

Most alarmingly of all, however, Crowther says that his idea for a trillion trees has been misconstrued as a green light to keep carbon emissions high. By promising to “offset” these emissions by planting trees, organizations have been able to avoid tackling the main problem, which is of course the need to reduce emissions.

“When you talk about planting trees, it's two things,” says Crowther. “In one context, it's millions of local communities and indigenous populations and farmers planting trees for their own livelihoods. And we need that desperately.”

“But on the other hand, it's corporations buying up land and planting monocultures, which is terrible.”

To try and set the record straight, Crowther has co-authored a new study which argues that the best way to remove carbon from the atmosphere is to ensure the preservation of existing forests. 

This, he says, can best be achieved by investing in the Indigenous communities that have acted as custodians of the natural world for thousands of years.

The new study from Crowther and colleagues is published in Nature.

[H/T: Wired]

Editor's note: after consultation with Dr Crowther, this article has been updated to more accurately reflect the research being reported. The previous title, "Stop Planting Trees, Begs Guy Who Urged World To Plant A Trillion Trees", was inaccurate, and has been changed to "The Trillion Trees Campaign Was Never About Planting A Trillion Trees". Quotes from Dr Crowther have also been added.