Last October, the Intergovernmental Panel on Climate Change (IPCC) released a damning report about the state of the planet, calling the world to action. To avert the worst of the climate crisis (which is already happening around us), carbon dioxide emissions need to fall by 45 percent by 2030.

Major economies, oil-producing countries, and private companies have been slow at heeding the warning or have actively worked against the future of our planet. A lot of the focus has been on personal responsibilities rather than what governments should be doing. While the picture is dark, it is not all over. Researchers are working tirelessly to find new solutions. A new proposal, published in Science, gives a simple solution to our carbon dioxide woes: plant more trees.

Researchers from ETH Zurich have estimated that under current climate conditions, our planet could support 1.6 billion hectares (3.9 billion acres) of extra forest, which would add to the 2.8 billion hectares (6.9 billion acres) that already exist. Not all of that could be reforested, but the team estimates that about 0.9 billion hectares (2.2 billion acres), an area roughly the size of the United States, could still be used to plant new trees.

"One aspect was of particular importance to us as we did the calculations: we excluded cities or agricultural areas from the total restoration potential as these areas are needed for human life," lead author Dr Jean-François Bastin said in a statement.

The question is how much carbon dioxide would these new forests sequester? The answer is a lot. Once mature they would store 205 billion tonnes (225 billion tons). That is just over two-thirds of all the CO₂ we have released into the atmosphere since the Industrial Revolution.  

"We all knew that restoring forests could play a part in tackling climate change, but we didn't really know how big the impact would be," co-author Professor Thomas Crowther added. "Our study shows clearly that forest restoration is the best climate change solution available today. But we must act quickly, as new forests will take decades to mature and achieve their full potential as a source of natural carbon storage." 

While it would be lovely if anyone on the planet decided to plant a few trees, it is important to make clear that this reforestation project would need to be an international effort. The top six countries that have the greatest potential for this project are, in order, Russia (151 million hectares), the US (103 million hectares), Canada (78.4 million hectares), Australia (58 million hectares), Brazil (49.7 million hectares), and China (40.2 million hectares). But every country can do its part.

The researchers want to determine which areas will have the biggest climate change impacts, set realistic goals, and continue to monitor progress. If reforestation is undertaken to the extent suggested by this study, it might provide precious time to get our act together and deal with greenhouse gas emissions for good. We just need political leaders that are brave enough to take on the challenge of saving us from ourselves.