Ed Butler speaks to Professor Tom Crowther from the Swiss university ETH Zurich, who says planting billions of trees around the world is by far the biggest and cheapest way to tackle climate change. Marcelo Guimaraes, chairman of Mahogany Roraima, a commercial timber and reforestation plantation in the northern Amazon rainforest, discusses how that would work in practice.
(Photo: A tree in a deforested area of the Amazon rainforest, Credit: Getty Images)
