An area of 900 million hectares could be planted with at least one trillion trees around the world to effectively combat global warming, researchers at the Federal Institute of Technology in Zurich (ETH Zurich) have calculated.
Once they have grown, the trees could store 205 billion tonnes of carbon, according to a study by Jean-François Bastin and Tom Crowther from ETH Zurichexternal link, which has been published in the latest edition of the journal Science.
This represents about two-thirds of the 300 billion tonnes of carbon that has been released into the atmosphere as a result of human activity since the Industrial Revolution.
The researchers say most of the benefit will come early on because trees remove more carbon from the air when they are younger. The potential for removing the most carbon is in the tropics.
Six countries with the most space for new trees are Russia, the United States, Canada, Australia, Brazil and China.
The researchers used Google Earth and artificial intelligence to see what areas could support more trees, while leaving room for people and crops. Bastin estimated there's space for at least 1 trillion more trees, but it could be 1.5 trillion.
“We all knew that restoring forests could play a part in tackling climate change, but we didn’t really know how big the impact would be. Our study shows clearly that forest restoration is the best climate change solution available today,” said Crowther. “But we must act quickly, as new forests will take decades to mature and achieve their full potential as a source of natural carbon storage.”