Image Credit: CIAT via Flickr // CC BY-SA 2.0

The Amazon is the largest tropical rainforest in the world. Spanning 2.1 million square miles and nine countries across South America, it’s one of the most biodiverse regions on Earth, with more than 400 new animal and plant species discovered there since 2010. So how many trees make up this massive ecosystem?

According to a study by dozens of biologists and conservationists using statistical models, the Amazon is home to an estimated 390 billion trees and 16,000 diverse tree species.

These trees play a vital role in the global ecosystem. The Amazon holds up to 17 percent of the world’s terrestrial carbon stores. However, a relatively small fraction of these 16,000 tree species play an outsize role in storing carbon. According to recent research in the journal Nature Communications, only 1 percent of Amazonian tree species is responsible for 50 percent of the forest’s carbon storage.

Trees’ ability to suck carbon out of the atmosphere makes them an important shield against further climate change, which is why emission-heavy China recently started planting a “Green Great Wall” of trees. China has planted 32 million acres of new forests since 2008, offsetting the carbon storage lost to deforestation in tropical forests like the Amazon, where deforestation rates are on the rise again. Looks like 390 billion-odd trees is not enough.