Planting billions of trees globally is by far the most impactful – and affordable – way to tackle the climate crisis, according to the scientists behind a new study. They have calculated that 0.9bn hectares of land worldwide are suitable for reforestation, and that planting new trees in these areas could remove two-thirds of all the emissions that human activity has sent into the atmosphere. The scientists described the figure as “mind-blowing”. The Crowther Lab of ETH Zurich has published…