The 300-Year Quest to Find Every Tree Species in the Amazon

How many different kinds of trees grow in the Amazon?

This may sound like an impossible question to answer—we’re talking about the most biodiverse rainforest on Earth. Hundreds of thousands of different plants and animals live there, with more being discovered every year.

In 2013, Field Museum ecologist Nigel Pitman and fellow scientists estimated that there are 16,000 different trees growing in the Amazon. But confirming that guess meant actually counting all of the known species. This process involved working with museums all over the world and looking at half a million specimens collected over the last 300 years, from 1707 to 2015.

Now we’re closer than ever to knowing how many species of Amazonian tree really exist: Dr. Pitman and his colleagues recently created the first checklist of all 11,676 unique kinds of tree that have been discovered so far in the Amazon.

Based on how many new trees are identified every year, it’s a good guess that the last unknown species of Amazonian tree will be discovered 300 years from now. The 4,000 or so tree species that remain to be found are extremely rare. In fact, many of them probably exist in parts of the rainforest where humans have never set foot.

The Field Museum has been a hotspot of research on Amazonian trees for the last 100 years. Today, discovering a new tree species in the Amazon still requires the same field effort that it did a century ago: collecting specimens, pressing, drying, and labeling them, and then hauling them back to an herbarium (that’s a collection of dried plants). But because The Field Museum and museums around the world are now making their specimens publicly available through digitization, the identification process can happen faster. Thousands of specimens of Amazonian trees in The Field Museum’s herbarium are digitized, and anyone with an internet connection can search and view them.

Since the Amazon is so dense with plant life but poorly studied, new discoveries are commonplace. For example, the specimen shown here was collected from a site in Brazil in 1945, and for 70 years the species wasn’t seen again—until February 2016, when the Museum’s rapid inventory team found the same species in Peru and took the first photos of the living plant. As scientists gain a better picture of what types of trees are growing in the Amazon and where, this information can be used to protect the world’s most diverse forest.

For more in-depth information, the full scientific paper by Hans ter Steege of the Naturalis Biodiversity Center, Nigel Pitman, and colleagues can be found here: “The discovery of the Amazonian tree flora with an updated checklist of all known tree taxa.”