A new study reports that recently established forests on abandoned farmland in Latin America, if allowed to grow for another 40 years, would probably be able to suck at least 31 billion tons of carbon dioxide out of the atmosphere.

That is enough to offset nearly two decades of emissions from fossil-fuel burning in the region. Abandoning additional pastures and allowing them to revert to tropical forest could soak up another seven billion tons of the gas, the scientists found.

Their paper, published in Science Advances, offers the most detailed estimates to date for a promising approach to combating climate change. Many Latin American governments have promised to encourage forest regrowth, as well as to combat the destruction of existing forests, in their long-term climate plans. But how hard they will push on either issue is unclear.