The first week of the COP26 climate talks in Glasgow, Scotland, saw a global pledge to cut emissions of the climate super-pollutant methane, more than 40 countries promise to phase out coal and 20 agree to stop public funding for some fossil fuel projects. 

But to stop global warming soon, the world needs to remove a lot of the greenhouse gases already in the atmosphere. In Glasgow, the gathered heads of state once again made it clear that they are counting on the world’s forests to do much of that work, with a new proclamation by 133 countries to halt global deforestation by 2030 and to try and restore degraded woodlands. 

Environmental activists and foresters question whether world governments can make good on their pledge to stop cutting down trees and instead restore forests. Many governments that joined the proclamation have failed on such commitments in the past. And some scientists doubt that trees can do as much work for the climate as many claim, even if they remain standing.

In similar pledges—the 2014 New York Declaration on Forests that aimed to halve deforestation by 2020, and the Trillion Trees plan announced at the World Economic Forum in Davos in 2020—world leaders also highlighted forests’ ability to soak up some of the increasing industrial greenhouse gas emissions they can’t seem to control. Yet, since the launch of those high-profile initiatives, forest loss has soared, with 99,614 square miles cleared in 2020 alone, according to the latest data from Global Forest Watch.

Cutting forest loss down to zero in the next eight years is daunting, but at the climate talks, United States President Joe Biden said protecting forests is an “indispensable piece of keeping our climate goals within reach,” with the potential “to reduce carbon globally by more than one third.” 

The agreement includes countries with forests that are critical to the global climate, like Brazil and Indonesia, and also has a new focus on clarifying Indigenous forest ownership rights, which Rod Taylor, global forest director with the World Resources Institute, an environmental policy think tank, saw as a small sign of progress. 

Of course, forests can’t reduce global carbon by a third, but they can take up and store some of the carbon dioxide emissions from burning fossil fuels. Exactly how much of that they can do in the future remains a huge question mark. In a best-case scenario—preserving all remaining old-growth forests and regrowing forests where possible—woodlands might continue to absorb about 30 percent of those emissions. 

But that won’t reduce atmospheric carbon nearly enough to stop climate change, and recent research shows that many global forests are so stressed they may not be able to keep scrubbing human pollution from the atmosphere at the same rate they have historically. 

Related: Many Overheated Forests May Soon Release More Carbon Than They Absorb

False Hope?

Some forest and climate scientists worry that the focus on forest protection and restoration is another way to deflect attention from the urgent need to immediately cut greenhouse gas emissions, a strategy that could enable leaders to say later that they tried to reduce the amount of carbon in the atmosphere, but that the trees didn’t cooperate.

“Forests are an essential tool in our battle against emissions … however, they are not the panacea and if we keep emitting as we are, they cannot cope,” said Alistair Jump, a global change researcher at the University of Stirling in Scotland. “Healthy and thriving forests lock up carbon as they grow, but that carbon is released when forests are cleared, when the trees die and decompose, or released super-fast if they burn.”

Trees can’t keep up with human emissions of CO2, he said, and the changing climate is actually making it difficult for some forests to absorb carbon from the atmosphere.

“They also soak up CO2 far slower than we are releasing it from fossil fuels,” he said. “That CO2 is changing the climate, which will result in forests in many areas being less adapted to their future climate, less capable of soaking up CO2 and in some cases—as we already see —actually emitting it as the trees sicken and die.”

“That way lies irreversible ecological breakdown. The simple message is that if we are to avoid the most devastating impacts of climate change we absolutely must keep fossil fuels in the ground.”

Biden’s statement is a meaningless oversimplification that could confuse people about the role of forests in the climate system, said carbon cycle scientist Scott Denning at Colorado State University.

“Forests are made of carbon,” he said. “Killing them converts their carbon into CO2. Growing them converts CO2 into forests. So anything we do to prevent forests from being destroyed (by fire, logging, agriculture, disease, etc.) reduces CO2 emissions. This doesn’t reduce the amount of CO2 in the air, it just reduces the rate at which CO2 is increasing.”

Growing new forests could help remove additional carbon dioxide from the atmosphere, but most places on Earth can’t support woodlands, he said. “Most places that could sustain forests already have forests. Most places that could have forests but don’t have forests are valuable land that’s being used to grow food or house cities,” he said.

Switzerland-based forest and climate researcher Constantin Zohner, with the Crowther Lab at ETH Zürich, said Biden’s statement on forests “clearly” referenced a 2019 study he co-authored, which showed that “if we would restore forests on all areas that would naturally support trees, excluding urban and agricultural areas, they would absorb approximately one third of the excess carbon humans have added to the atmosphere.” 

Related: Can Planting a Trillion Trees Stop Climate Change? Scientists Say it’s a Lot More Complicated

Efforts to boost the role of forests in scrubbing CO2 from the air will only work “if ecosystem restoration is implemented as a bottom-up process, where local communities work together to make nature the most economically sustainable solution,” he said. Biden’s remarks seem to reflect an understanding “that it’s all about the ecosystem as a whole and not just about planting trees to absorb carbon,” he said.

“Restoration must understand the local ecology and the local economy. And I would also argue that we need to get away from the simplistic view of seeing forests only as a carbon sink,” he said. “Carbon sequestration comes naturally if we manage to maintain healthy ecosystems, but it should never be seen as the sole purpose of a forest or any other ecosystem type.” 

Brazil and Indonesia Sign Pledge, But Continue Cutting

Days after the Indonesian president signed the pact, the nation’s environment minister, Siti Nabaya Bakar, criticized it as “inappropriate and unfair.”

“The ongoing development of President [Joko Widodo’s] era must not stop in the name of carbon emissions or in the name of deforestation,” she wrote on social media.

Forest experts with Greenpeace said the deforestation agreement lacks teeth and green-lights at least another decade of unabated logging that will further harm the climate. That made it easy for countries with critical forests and high rates of deforestation, like Indonesia and Brazil, to sign on.

“There’s a very good reason Bolsonaro felt comfortable signing on to this new deal,” said Greenpeace Brazil executive director Carolina Pasquali. “It allows another decade of forest destruction and isn’t binding. Meanwhile the Amazon is already on the brink and can’t survive more years of deforestation.”

Pasquili suggested world leaders look to the Indigenous people who are calling for 80 percent of the Amazon to be protected by 2025, rather than the pact announced in Glasgow. “They’re right, that’s what’s needed,” she said. “The climate and the natural world can’t afford this deal.”

Destruction of the Amazon increased Brazilian greenhouse gas emissions by 9.5 percent, “the result of deliberate policy choices by the Bolsonaro government,” she said. Greenpeace warned, given Bolsanaro’s track record, there is little chance he would abide by the entirely voluntary agreement. In fact, “he is currently trying to push through a legislative package that would accelerate forest loss,” she said.