We’re in a bit of a pickle. Our modern lifestyles and economies are based on vast energy needs, which are largely met by the burning of fossil fuels. Yet transitioning to low-carbon energy sources on a large enough scale will take decades. Meanwhile, we’ve already pumped such massive amounts of greenhouse gases into the atmosphere that we’re changing the planet’s climate.
One solution is to plant trees to suck excess carbon dioxide out of the atmosphere. But we’ll need lots and lots of trees. We’ll need 1.2 billion of them, to be precise. By planting that many trees across the planet, in woods and parks and elsewhere, we could offset a decade’s worth of CO2 emissions, according to British ecologist Thomas Crowther.
At present, according to his calculations, there are around 3 trillion trees on earth, way more than the previous estimate of 400 billion. Even so the number of trees on Earth has nearly halved since the Agricultural Revolution began some 10,000 years ago.
“There’s 400 gigatons [of CO2 stored] now, in the 3 trillion trees, and if you were to scale that up by another trillion trees that’s in the order of hundreds of gigatons captured from the atmosphere – at least 10 years of anthropogenic emissions completely wiped out,” the ecologist explains.
Better yet: planting trees is a simple activity that can be done pretty much by anyone anywhere. “It’s a beautiful thing because everyone can get involved,” Crowther notes. “Trees literally just make people happier in urban environments, they improve air quality, water quality, food quality, ecosystem service, it’s such an easy, tangible thing.”
However, other scientists have questioned the idea that planting more trees alone will help heal the planet. They argue that unless we rein in our carbon emissions drastically, not even a billion more trees can help.
“If we continue burning coal and oil the way we do today and regret our inaction later, the amounts of greenhouse gas we would need to take out of the atmosphere in order to stabilize the climate would be too huge to manage,” said Lena Boysen, the lead-author of a recent study published in Earth’s Future, a journal of the American Geophysical Union.
“Even if we were able to use productive plants such as poplar trees or switchgrass and store 50 percent of the carbon contained in their biomass,” she added, “in the business-as-usual scenario of continued, unconstrained fossil fuel use the sheer size of the plantations for staying at or below 2°C of warming would cause devastating environmental consequences.”
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