Directions for teachers: Ask students to read the online Science News article “Earth may have 9,200 more tree species than previously thought,” which describes researchers’ efforts to estimate the number of tree species on Earth, and answer the following questions. A version of the article, “Earth may be hiding thousands of tree species,” appears in the March 12, 2022 issue of Science News.

1. How many types of trees, or tree species, do scientists know about?


There are about 64,100 known tree species on Earth.

2. How many tree species have yet to be discovered, according to scientists’ calculations? What is the new estimate for the total number of tree species?   

There could be roughly 9,200 tree species that have yet to be discovered, scientists estimate. That means Earth could have about 73,300 tree species.

3. In your own words, describe the methods that scientists used to reach their findings.

The researchers analyzed global forest data, using statistics to calculate how many species might exist. Subtracting the number of species known to science from that number gave the team an estimate of how many species might still await discovery.

4. Why haven’t the undiscovered tree species been found yet? Where might researchers discover many of these species?


Many of the tree species probably haven’t been found yet because they are rare. And they probably live in regions with a lot of biodiversity such as the Amazon in South America.

5. What implications does the research have for the world’s biodiversity, according to biologist Roberto Cazzolla Gotti?

Being able to estimate how many plant and animal species there are, and where they live, could help researchers figure out where to target efforts to preserve and restore biodiversity.

Sign up if you’re interested in receiving free Science News magazines plus educator resources next school year. The Society for Science’s Science News Learning program serves nearly 5,000 public high schools across the United States and worldwide.

Learn More