Tom Crowther is a climate change ecologist at Swiss university ETH Zurich. Four years ago he found there are about 3 trillion trees already on earth — much higher than NASA’s previous estimate of 400 billion. Now, his team of researchers has calculated there is enough room on the planet for an additional 1.2 trillion — and that planting them would have huge benefits in terms of absorbing atmospheric carbon dioxide, the main driver of climate change.

“The amount of carbon that we can restore if we plant 1.2 trillion trees, or at least allow those trees to grow, would be way higher than the next best climate change solution,” Crowther told CNN.