ATMOSPHERE - In recent years, climate change has loomed like a dark specter over the globe, contributing to everything from gentrification in Miami to refugees fleeing drought and crop shortages in Guatemala. But the urgency around the issue reached new heights in 2018 when the United Nations' Intergovernmental Panel on Climate Change (IPCC) stated that rapid, "far-reaching and unprecedented changes in all aspects of society" would be needed in order to drop carbon dioxide levels by 2030 and prevent catastrophic global warming.
Scientists have indeed proposed drastic measures — just not in the way that you might think. In the same IPCC report, the UN suggests that adding 2.5 billion acres (1 billion hectares) of forest to the world could limit global warming to 2.7 degrees Fahrenheit (1.5 degrees Celsius) by 2050. In other words: Responding to climate change will require planting new trees. A lot of them.
And now, the UN might just have the data to back up their proposal.
In another study, unveiled July 5, 2019 in the publication Science, a group of researchers associated with the Crowther Lab in Switzerland found that global tree restoration to the tune of 223 million acres (900 million hectares) of canopy cover — an area that's approximately the size of the U.S. — is "our most effective climate change solution to date." These trees would store 205 billion tons (186 metric tons) of carbon, or roughly two thirds of the carbon that has been emitted "as a result of human activity since the Industrial Revolution," according to a press release. Although some news reports have said this much forest restoration is the equivalent of roughly 1 trillion trees, this statistic is actually linked to an estimate from an older 2015 report.
The study's lead author, Jean-François Bastin, breaks down the analysis by email. "The idea was to estimate what tree cover could be expected when you removed the 'human factor,' i.e. what specific types of forest would naturally occur in the absence of other development, and where," says Bastin. The team used a form of artificial intelligence known as "machine learning" to build "a model to link tree cover with climate/soil/topography, based on 78,000 observations of tree cover in protected areas."
The researchers then projected the data further to estimate the "total potential tree cover of the planet," says Bastin. Afterward, the team excluded land currently being used for urban settlements, croplands and existing forests, which yielded the total amount of land available for restoration. The study offers a map showing how much tree coverage different parts of the globe can support; the top three areas include Russia, Canada and the U.S.
A Worldwide Effort at Reforestation
In many ways, the study's timing couldn't be more perfect, as it aligns with current global efforts around ecological restoration. One example is the Trillion Trees Vision, which seeks to restore 1 trillion trees by 2050. Another is the Bonn Challenge, which is a partnership between the government of Germany and the UN's International Union for Conservation of Nature that aims to restore 371 million acres (150 million hectares) of deforested land by 2020.
You might be thinking, well, that sounds pretty easy. Let's all roll up our sleeves and save the planet by planting one tree at a time — right? But some experts say the situation is actually a little more complicated than that rosy picture. Especially if most nations don't chip in to help.
"Implementation of forest restoration on the scale discussed in this paper is not as straightforward as it might seem," says Jim Hallett, chair of the board of directors for the Society for Ecological Restoration. "By 2018, there were commitments of over 420 million acres (170 million hectares) by 58 nations, which exceeds the Bonn Challenge goal. Current estimates indicate that around 29 percent of the committed lands are now under restoration, but most of this work has been done by a few countries."[HWS]