(Newser) – There are 3 trillion trees on Earth, but adding between 500 billion and 1.5 trillion more could help solve a big crisis on the horizon. New research in the journal Science proposes fighting climate change by planting enough new trees to cover 3.5 million square miles of land, or what the AP says is about the size of the entire United States. The new trees could theoretically suck up about two-thirds of the carbon dioxide that humans have spewed into the atmosphere since the 1800s, what scientists call a "mind-blowing" amount, per the Guardian. Much of the carbon quashing would come fairly quickly after such a massive tree-planting, as younger trees take in more carbon than older ones. "This is by far—by thousands of times—the cheapest climate change solution," and the most effective one, study co-author Thomas Crowther says.

The extra trees, which scientists estimate would cost around $300 billion, would also boost biodiversity, tamp down erosion, and help keep water clean. Whether the Earth has room for them is another matter, and researchers say yes, based on the 80,000 satellite pics they reviewed, along with data on what areas were conducive to tree growth. The nations that researchers point to as having the most room to spare: the US and Russia, as well as Canada, Australia, Brazil, and China. Critics tell Mother Jones the plan is "unrealistic," citing the ambiguity of what land would be available and the issue of how this restoration would affect agriculture. Still, Crowther says forest restoration is "overwhelmingly" the best way to put the kibosh on global warming, though he warns we should still keep trying to eliminate fossil fuels. "None of this works without emissions cuts," he notes. (The Amazon is losing forest land, quickly.)

