According to a news release from the Field Museum, there are nearly 400 billion individual trees growing in the Amazon. In addition, there are approximately 16,000 tree species.

Historically, the size and arduous terrain of the Amazon Basin has prevented the study of their amazingly diverse tree communities to local and regional scales. Unfortunately, this dearth of elementary data about the Amazonian flora on a basin-wide scale has hurt science and conservation efforts.

“In essence, this means that the largest pool of tropical carbon on Earth has been a black box for ecologists, and conservationists don’t know which Amazonian tree species face the most severe threats of extinction,” notes co-author Nigel Pitman, Robert O. Bass Visiting Scientist at The Field Museum.

Thanks, however, to the efforts of more than 100 experts, researchers have created the first basin-wide estimates of the quantity, frequency and spatial dispersion of thousands of Amazonian trees. Estimates from data gathered over a decade reveals that greater Amazonia contains approximately 390 billion individual trees.

“We think there are roughly 16,000 tree species in Amazonia, but the data also suggest that half of all the trees in the region belong to just 227 of those species! Thus, the most common species of trees in the Amazon now not only have a number, they also have a name. This is very valuable information for further research and policymaking,” posits first author Hans ter Steege, a researcher at the Naturalis Biodiversity Center.

The researchers called these species “hyperdominants.” While the study shows that hyperdominants account for about 50 percent of all carbon and ecosystem services in the Amazon, it also reveals that almost none of the 227 hyperdominant species are consistently common across the amazon. Instead, most reign over a region or forest type.

The research also provides information about the most uncommon tree species in the Amazon. For example, the study suggests that approximately 6,000 tree species in the Amazon have numbers of less than 1,000 individuals. In fact, these species are so uncommon that researchers may never locate them.

“Just like physicists’ models tell them that dark matter accounts for much of the universe, our models tell us that species too rare to find account for much of the planet’s biodiversity. That’s a real problem for conservation, because the species at the greatest risk of extinction may disappear before we ever find them,” professes co-author Miles Silman, an ecologist at Wake Forest University.

Silman refers to the phenomenon as “dark biodiversity.”

The researchers are still trying to determine why some species are hyperdominant and others are uncommon.

“There’s a really interesting debate shaping up,” notes Pitman, “between people who think that hyperdominant trees are common because pre-1492 indigenous groups farmed them, and people who think those trees were dominant long before humans ever arrived in the Americas.”

The study’s findings are described in greater detail in the journal Science.