All sorts of technological approaches have been proposed, but trees are an obvious contributor. New trees can either be planted in regions that have been deforested (reforestation) or in places that have never had them before (afforestation). As the trees grow, they pull in CO2 through their leaves and convert it into carbohydrates, which they use to grow. So long as a tree lives, that carbon stays within it – and trees can live for decades or centuries. Trees are a natural “carbon sink”. It follows that we should both stop chopping down forests – especially tropical ones like the Amazon, which store huge amounts of carbon – and start planting more.
By some estimates, trees can be an enormous carbon sink. A study published in July 2019, led by Thomas Crowther of ETH-Zurich in Switzerland, estimated the world has room for an extra 0.9 billion hectares of forest. Once those trees had matured, they could store 752 billion tonnes of CO2. Planting trees is one of the most effective carbon drawdown solutions to date.
