As temperatures rise and wildfires rage from Canada to Australia, forests have become a symbol of danger in a warming world. They may also be one of our best hopes for capturing and storing the unsustainable levels of carbon dioxide that humans have released into the atmosphere. “If we can do it right,” says British ecologist Thomas Crowther, “the conservation and restoration of forests can potentially buy us some time as we try to decarbonize our economies.”
A recent study that Crowther co-authored in Science points to nearly a billion hectares of non-urban, nonagricultural land on Earth that could be reforested — ultimately capturing as much as 200 gigatons of atmospheric carbon. To date, human industrial activity has added 300 gigatons of excess carbon to the atmosphere.
Crowther says we have long known about the role of forests as carbon sinks. “But this helps to understand the scale of what is possible.” (Basic Earth science refresher: Trees absorb carbon dioxide from the atmosphere and turn it into wood. This trapped carbon is stored not only in the living trees, but also, over time, in the soils of the forest floor.)
The undertaking would be massive — replanting an area the size of the United States — primarily across Russia, the U.S., Canada, Australia, Brazil, and China. But the study also cautions that the window of opportunity is closing. If allowed to rage unabated, global warming will soon destabilize and diminish existing forests. “Restoration will achieve nothing if we do not conserve what we currently have,” says Crowther.
At the World Economic Forum in Davos, President Trump highlighted the One Trillion Trees initiative, which seeks to jump-start global reforestation. Marc Benioff, the CEO of Salesforce and a trustee of the WEF, took credit for getting the idea in front of Trump in an interview with Rolling Stone. Benioff touts the appeal of a project he believes can unite governments, industry, and activists, through the platform that he and WEF are building at 1t.org. “We need to cut emissions, and we need to sequester carbon — and we all need to get on it,” says Benioff, who ballparks the cost of reforestation at $300 billion. If the Trump administration can get behind reforestation, he believes, that’s an important first step. “I hope that Democrats and Republicans can come together and agree on the tree. If the tree is not the ultimate bipartisan issue,” he says, “I don’t know what is.”
Some environmentalists fret, however, that tree planting could be used as “greenwashing” by carbon polluters while avoiding the much harder work of rejecting fossil-fueled growth. “Planting trees is good,” said Greta Thunberg, “but it’s nowhere near enough.” Scientists back her up. “If tree planting is just used as an excuse to avoid cutting greenhouse-gas emissions,” Crowther says, “then it could be a real disaster.”