Planting 1 trillion trees might not actually be a good idea

The World Economic Forum’s plan to plant 1 trillion trees is backed by controversial science

Tree-planting campaigns have taken off, with everyone from YouTube creators to high-powered CEOs embracing trees as a solution to the climate crisis. But even as the arboreal campaigns have grown, dozens of scientists have warned that planting all those trees could potentially cause more harm than good. Others point to another solution with a more proven track record and that might be more deserving of global support — empowering the people who live in and safeguard forests already.

Trees just got a big boost at The World Economic Forum this month, when the forum announced a new initiative aimed at planting 1 trillion trees around the globe within the decade to combat climate change. It’s got the backing of big names: Salesforce CEO Marc Benioff is contributing an undisclosed amount of his own cash to the effort, while his company has committed itself to planting 100 million trees. Even Donald Trump, who has thrown a wrench into US and global efforts to tackle climate change, said the US would sign onto the campaign, called 1t.org.

But the science behind the campaign, a study that claims 1 trillion trees can significantly reduce greenhouse gases, is disputed. “People are getting caught up in the wrong solution,” says Forrest Fleischman, who teaches natural resources policy at the University of Minnesota and has spent years studying the effects of tree planting in India. “Instead of that guy from Salesforce saying, ‘I’m going to put money into planting a trillion trees,’ I’d like him to go and say, ‘I’m going to put my money into helping indigenous people in the Amazon defend their lands,’” Fleischman says. “That’s going to have a bigger impact.”

Tree-planting started really trending in 2019, when a study published in the journal Science caused a commotion. It claimed that planting a trillion trees could capture more than a third of all the greenhouse gases humans have released since the industrial revolution. After the initial media blitz rallied excitement for the seemingly simple climate solution, a group of 46 scientists, including Fleischman, responded to the study with their critique.

“Headlines around the world declared tree planting to be the best solution to climate change,” lead author of the critique Joseph Veldman said in a statement at the time. “We now know those headlines were wrong.” Veldman argued that planting trees where they don’t belong can harm ecosystems, make wildfires worse, and even exacerbate global warming. His critique made the case that the amount of carbon the study said 1 trillion trees could sequester was about five times too large. The study also considered planting trees on savannas and grasslands, where planting non-native trees could cause problems for local species. Planting trees on snowy terrain that once reflected the sun could even turn those places into dark patches that actually absorb heat.

The authors of the contested study stand by their work. “We are aware of no other viable climate change solution that is quantitatively as large in terms of carbon drawdown,” the authors from the Crowther Lab at ETH Zurich said in their comments published in Science last October.

To be clear, critics of the campaign are still fans of trees. They still think forests play a role in solving the climate crisis — their skepticism mostly centers around efforts to plant trees in places they weren’t before, or to plant large swaths of a single species to essentially create “tree plantations” instead of real forests. Another big concern surrounding the call for planting a trillion trees is that it could distract from other efforts to slow down climate change, like stopping fossil fuel pollution and deforestation in the first place.

“You don’t need to plant a tree to regenerate a forest,” Fleischman tells The Verge. Forests can heal on their own if they’re allowed to, he says, and these forests end up being more resilient and more helpful in the climate fight than newly planted plots of trees. He argues that the best way to ensure there are enough trees standing to trap the carbon dioxide heating up the planet is to secure the political rights of people who depend on forests — primarily indigenous peoples whose lands are frequently encroached upon by industry and governments.

There is research backing him up. The world’s leading authority on climate science, the United Nations Intergovernmental Panel on Climate Change (IPCC), has recognized that when local communities’ land rights are jeopardized, it poses risks to both people and the planet.

“We have cared for our lands and forests — and the biodiversity they contain — for generations. With the right support we can continue to do so for generations to come,” reads a statement from indigenous and community organizations from 42 countries spanning 76 percent of the world’s tropical forest in response to a report from the IPCC.

A study published this week in the journal PNAS found that the most effective way to protect the Amazon rainforest might be to leave it in the hands of its indigenous residents. The Amazon now releases more carbon dioxide than it stores, in large part due to forest loss from mining, logging, agriculture, and fires. The study also looked at regions that were best able to stop that from happening, and found that indigenous territories had the best success rates. Between 2003 and 2016, lands under indigenous control had the smallest losses of carbon because the forest stayed intact and regrew in places that had been disturbed.

The study also warned that the ability of indigenous peoples to protect their lands is under threat. Brazilian president Jair Bolsonaro has been accused of encouraging the genocide of indigenous tribes at the same time that he’s pledged to open up more parts of the Amazon for development.

The lead author of that study, however, cautions against pitting all tree planting efforts against forest conservation. “It’s not like these two things are in competition,” says Wayne Walker, a scientist at the Woods Hole Research Center. Maintaining existing forests should be a priority, but restoring trees to places where they’ve been lost can sometimes be the next best option, he says.

Still, not all tree-planting initiatives are created equal. The location, species planted, and how people are involved can all jeopardize success.

In India, leading environmental groups opposed a project to plant 2 billion trees in the Cauvery river basin supported by the Leonardo DiCaprio Foundation. They claimed in a letter that the campaign threatened to dry up streams and destroy habitats. People who live alongside and depend on the river would be affected too, says Prakash Kashwan, a political science professor at the University of Connecticut.

Organizers of the Cauvery tree-planting project have said the criticism against it is “a baseless opinion that contains blatant untruths and loose comments with no backing in facts.” It says the trees will revive the river by increasing water retention. The founder of the foundation that launched it, yogi and author Sadhguru, joined Salesforce’s Benioff at a press conference for the trillion trees campaign in Davos. That global initiative could help his project “scale this up to 50 to 60 billion trees across the country,” Sadhguru said on the panel.

That worries Kashwan. The buzz generated by big international campaigns can give prestige to projects that have been rejected on the ground. “They get new lives because you know, the World Economic Forum is talking about it,” he says.