Assuming everything goes to plan, over the next six years, the Amazon rainforest will get 73 million new trees. The mass planting is part of a project sponsored by Conservation International, the Brazilian Ministry of Environment, and a number of other NGOs and corporations. As John Converse Townsend at Fast Company reports, it is the largest tropical reforestation effort ever attempted.

According to a press release from Conservation International, the effort will span deforested pasture lands over a 74,000-acre region spanning several Brazilian states—with the greatest focus in Southern Amazonas, Rondônia, Acre, Pará and the Xingu watershed. The purpose of the project is, in part, to revive the 20 percent of the Amazon that has been lost to deforestation due to agriculture and pasturing during the last 40 years. But the effort is also geared toward learning how to restore tropical forests.

“This is a breathtakingly audacious project,” says M. Sanjayan, CEO of Conservation International, according to the release. “The fate of the Amazon depends on getting this right—as do the region’s 25 million residents, its countless species and the climate of our planet.”

As Townsend reports, reforestation efforts are typically very costly and time consuming—requiring people to both grow and plant thousands of saplings, many of which will not survive. In this latest effort, the restorationists are trying a new method called muvuca, in which they will spread the seeds of native trees across the slash and burned land and animal pastures. The seeds come from the Xingu Seed Network, which uses a coalition of 400 collectors to gather the seeds from native trees.

“With plant-by-plant reforestation techniques, you get a typical density of about 160 plants per hectare,” Rodrigo Medeiros, vice president of Conservation International’s Brazil program, tells Townsend. “With muvuca, the initial outcome is 2,500 [trees] per hectare. And after 10 years, you can reach 5,000 trees per hectare. It’s much more diverse, much more dense, and less expensive than traditional techniques.”

The muvuca experiment is the beginning of a massive effort announced by Brazil to restore 12 million hectares of forest, an area the size of Pennsylvania, as part of an effort to reach their climate change goals under the Paris Accord. Recent studies show that second growth forests—those less than 60 years old that grow after logging or land clearance—can sequester huge amounts of carbon. As Townsend reports, just stopping current deforestation could help mitigate 37 percent of current carbon emissions. Planting or restoring forests could make that number even bigger.

While the effort is impressive, it’s not the largest reforestation effort in the world. In July, 2016, 800,000 people in Uttar Pradesh, India, planted 50 million trees in just 24 hours, a publicity stunt to highlight India’s Paris Accord commitment to reforest 12 percent of its land by 2030. The world’s largest program, however, is China’s Grain-for-Green effort, a plan to restore 69.2 million acres of forest land, which is an area the size of New York and Pennsylvania combined.

All of these efforts are encouraging, but replanting is only half of the solution. Twenty-five million acres of forests are cleared each year, writes Doug Boucher, Director of Climate Research and Analysis at the Union of Concerned Scientists. He points out that while the long-term benefits of reforestation are helpful for the climate, the decades it takes for forests to regrow means it will take a while to see benefits. This means other more immediate solutions, such as reducing industrial emissions and halting the removal of forests, are still necessary to make a dent in our changing climate.