Types of trees in the amazon rainforest

The Amazon rainforest is so vast, and so diverse, that seemingly simple questions— such as which species of trees are most common— remain unanswered. Researchers are finally seeing the forest and the trees after an international collaboration of 120 scientists teamed up to compile the largest tree survey ever assembled from the Amazon.

The report, from the Oct. 18 issue of Science, estimates that about 16,000 tree species grow in the world’s largest rainforest. To the surprise of scientists, however, just 227 “hyperdominant species” account for half of all the trees. The findings may inform future studies of how the rainforest adapts to climate change.

Hans ter Steege, a tropical forest ecologist at the Naturalis Biodiversity Center in the Netherlands, recruited researchers to join the Amazon Tree Diversity Network. Hundreds of scientists labored for years to count and identify more than 500,000 trees in 1,170 study sites scattered throughout the rainforest. Team members extrapolated the total number of tree species in the Amazon and projected habitat ranges for the most common species.

“For the first time, we can estimate the population sizes of so many species,” ter Steege told mongabay.com. “I think we’ve given the Amazon a face.”

The 227 hyperdominant species represent less than 2 percent of the total tree varieties that researchers encountered—far fewer than the 1,000 species ter Steege had expected. Most such trees thrive only in specific habitats, such as swamps or white-sand forests.

The most common canopy member is a palm tree, called Euterpe precatoria. The forest is also flush with Brazil nut trees and their relatives, and members of the Nutmeg family.

Despite the tremendous tree-counting effort, ter Steege still calls the endeavor “a very-large scale study with a very, very small sample size.” The plots cover just 12 square kilometers—just 0.0002% of the Amazon.

To gauge how many species they missed, the researchers used a mathematical projection that ranked the species in order of how often they were found. The model then estimated how many more species were too scarce to even show up in plots. The projection predicted that 11,000 species escaped detection. More than half of them have populations of fewer than 1,000 trees, the scientists believe.

These mystery trees are the most susceptible to extinction through deforestation or climate change, the team stated. They qualify for the International Union for Conservation of Nature (IUCN) Red List of Threatened Species.

“It is a very impressive piece of work,” Chris Dick, a tropical forest ecologist at the University of Michigan, told mongabay.com. The tree estimates are accurate, he said, but they overlooked two major plant groups: shrubs and woody vines. “There might be an equal number of species—or more—that are just understory species,” Dick said.

Ter Steege is working with the World Wildlife Fund to pinpoint which tree varieties are protected in reserves and which are most at risk. He hopes to guide conservationists in consolidating existing parks or creating new ones to protect the rarest forest denizens.

The study cannot predict how the rainforest will respond to climate change. But it does help researchers focus their efforts on species most responsible for cycling carbon and water through the forest, said co-author Ken Feeley of Florida International University. “It gives me hope,” Feeley told mongabay.com. “It makes it much more of a tractable problem.”

CITATION: Ter Steege, H. et al. (2013) Hyperdominance in the Amazonian Tree Flora. Science 342 (6156)

Patricia Waldron is a graduate student in the Science Communication Program at the University of California, Santa Cruz.

The Amazon rainforest is awash in different types of trees — almost 12,000 species and counting, a new study finds.  

The new tally is the first time anyone has tried to accurately count how many species of trees live in the Amazon, the most diverse place for trees on Earth, the researchers said.

"The Amazon is a truly rich place in terms of biodiversity," said the study's lead researcher, Hans ter Steege, a senior research fellow at the Naturalis Biodiversity Center in the Netherlands. "Indeed, much of that diversity consists of rare to very rare species."[Amazon Photos: Trees That Dominate the Rain Forest]

In 2013, ter Steege and his colleagues estimated that there were approximately 16,000 tree species living in the Amazon. But no one had ever counted them all, and one anonymous reviewer of that research speculated that there were as few as 6,000 species.

"After a while, I was just curious how many species of tree had actually been collected in the area," ter Steege told Live Science in an email. So, he and his colleagues combed through tree records from 1707 to 2015. According to their findings, the Amazon is home to 11,676 species of trees, and there are likely more that have yet to be discovered.

"We interpret this to mean that our 2013 estimate of 16,000 species is good, and that about 4,000 of the rarest Amazonian trees remain to be discovered and described," study co-author Nigel Pitman, a senior conservation ecologist at The Field Museum in Chicago, said in a statement.

To investigate, the researchers downloaded all of the available data on plant collections from the nine Amazonian countries. This data — including photos and digital records — was housed on the Global Biodiversity Information Facility and SpeciesLink, two large online repositories of natural history collection data, ter Steege said.

"We needed to clean the data a lot (spelling errors, location errors), [and] take out the non-trees and collections not in the Amazon," ter Steege said.

As the researchers scrutinized records, they noted which years were the most fruitful for discovery. They found three major peaks: 1840, 1920 and 1980. For instance, there were only a few thousand specimens (each specimen can be for the same species) recorded before 1900 (just 5,696 in total), after which average collection rates rose to 839 specimens a year, the researchers wrote in the study.

After 1960, the collection rate rose to 10,380 a year. But in the past 10 years, these rates have declined, with 4,727 a year in 2000 to 2,636 a year for the past few years, the researchers said.

Some of these specimens turned out to be species that were new to science.

"Since 1900, between 50 and 200 new trees have been discovered in the Amazon every year," Pittman said. "Our analysis suggests that we won't be done discovering new tree species there for three more centuries."

The newly aggregated list will likely be a useful tool for ecologists studying the rainforest, the researchers said.

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