Study: Amazon Basin Is Home To About 16,000 Tree Species

Researchers say there are more than 16,000 species of trees in the Amazon Basin. 

New research shows that there are about 390 billion trees belonging to 16,000 species in the Amazon Basin.

Covering an area nearly the size of the 48 contiguous North American states, this basin-wide survey is the first to look at the full scale of the Amazon rainforest. The research is published in the Oct. 17 issue of the journal Science. Previous studies concentrated on local and regional flora.

"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, from the Field Museum in Chicago, said in a press release.

More than 100 experts analyzed 1,170 of those local and regional surveys, which were compiled over the course of a decade, to arrive at the basin-wide data. Moving from a regional to a basin-wide understanding will give researchers a clearer picture of threats to the flora.

While the researchers estimate that the overall total number of species is about 16,000, they say that more than half of the 390 billion trees are from 227 species.

"The finding that Amazonia is dominated by just 227 tree species implies that most biogeochemical cycling in the world's largest tropical forest is performed by a tiny sliver of its diversity," the authors wrote. "An appreciation of how thoroughly common species dominate the basin has the potential to simplify research in Amazonian biogeochemistry, ecology, and vegetation mapping. Such advances are urgently needed in light of the [more than] 10,000 rare, poorly known, and potentially threatened tree species in the Amazon."

About 6,000 of the species have fewer than 1,000 individual trees, indicating that they are eligible for the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. More than 500 tree species in South America are already listed on the IUCN Red List. Co-author Miles Silman of Wake Forest University acknowledged the importance of finding individual trees in these species before they go extinct.

The basin-wide study revealed that most of the species are native to specific regions, not throughout the overall forest. When a species does show up in multiple regions, it is usually in the same types of forest, such as swamps or uplands.

"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," said Pitman.