There are roughly 16,000 different tree species living in the 1.4 billion acres of dense forest that make up the Amazon, a new estimate suggests.

More than 100 experts gave data from 1,170 forestry surveys in all major forest types in the Amazon to determine how many trees there are in the South American rain forest and how many different tree species grow there. The study, published in the journal Science, reveals the region houses around 390 billion individual trees, including Brazil nut, chocolate, and açai berry 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!” Hans ter Steege, first author on the study and researcher at the Naturalis Biodiversity Center in South Holland, Netherlands, said in a statement. “Thus, the most common species of trees in the Amazon now not only have a number, they also have a name.”

Until recently, Amazonian trees were classified and located based on analyses of regions since the rain forest is too vast to survey -- making basic information like the common tree species unknown.

"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," Nigel Pitman, coauthor of the study from the Field Museum in Chicago, said.

According to the latest estimate, around 6,000 tree species in the Amazon have populations fewer than 1,000, making them eligible for the International Union for Conservation of Nature's Red List of Threatened Species -- but since they're so rare, scientists may never be able to find them.

The latest estimation involved cataloging trees with stems thicker than 3.9 inches at 1,170 different locations throughout the Amazon, LiveScience reports. Researchers have dubbed the 227 species that make up half the nearly 400 billion total trees in the Amazon, "hyperdominants."

While these species account for just 1.4 percent of all Amazonian tree species -- they make up roughly half of all carbon and ecosystem services in the Amazon. None are consistently found across the vast region, rather they dominate a particular region or forest type.

Despite the newfound figures of the extensive Amazon rain forest that encompasses parts of Brazil, Peru, Colombia, Guyana, Suriname, and French Guiana, there are still unanswered questions surrounding why the 227 hyperdominant species exist. One theory suggests hyperdominant species are resistant to disease and herbivores, according to LiveScience.

"There's a really interesting debate shaping up 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," Pitman said.