There are more than 9,000 types of trees we don’t know of yet, study finds

By Danya Gainor and Angela Dewan, CNN

A new tropical tree species discovered in Cameroon was recently named after actor and climate advocate Leonardo Di Caprio, who had campaigned against rampant deforestation in the African nation. A new study suggests the world may need to come up with a long list of other climate champions soon, with researchers estimating there are still 9,000 types of trees yet to be discovered, let alone named.

While most people may struggle to name more than a dozen tree species, the study, published in the Proceedings of the National Academy of Sciences, pooled data from around the world to show that there are roughly 73,000 types of trees on Earth, and some 9,200 are unaccounted for.

Almost one-third of the undiscovered tree species are likely to be rare with limited dispersion, said the study authors, making them especially vulnerable to climate change.

In South America, where over 40% of the undiscovered tree species are believed to live, the climate has been historically stable, meaning the flora hasn’t evolved to adapt to sudden changes.

But as the climate crisis brings more extreme weather and changes in temperature and precipitation patterns, researchers say these South American trees, in particular, will find it hard to survive.

Peter Reich, a co-author on the study and the Director of the Institute for Global Change Biology at the University of Michigan and Distinguished McKnight University Professor at the University of Minnesota, said this study is about knowing what we’ve got before it’s gone.

“We know that we’re losing trees to deforestation and climate change — species are going extinct. And that’s important,” Reich said. “But actually, knowing what you have before you lose it is important.”

Trees are one of the world’s biggest and most widespread flora and are a significant part of the planet’s biodiversity. They pull carbon dioxide out of the air, produce breathable oxygen and are home to many insects and birds. Biodiversity among trees is imperative for the stability of forest ecosystems, according to the study, and estimating populations of tree species makes it easier to prioritize conservation efforts as climate change tightens its grip on the planet.

“By establishing a quantitative benchmark, this study could contribute to tree and forest conservation efforts and the future discovery of new trees and associated species in certain parts of the world,” Reich said in a press release.

This research highlights how little we actually know about the magnificent organism and has left researchers wanting to learn more.

“These kinds of studies help us understand how resilient [trees] are likely to be in the face of climate change,” said Reich. “And the less resilient they are just adds more information and pressure on us to solve the climate crisis sooner rather than later.”

Researchers combined two sources of data — from the Global Forest Biodiversity Initiative and TREECHANGE — to create the world’s largest forest database. After marrying the two datasets, researchers used a statistical model with data on the known tree species to estimate how many are likely still undiscovered.

“Each set comes from someone going out to a forest, standing and measuring every single tree — collecting information about the tree species, sizes and other characteristics. Counting the number of tree species worldwide is like a puzzle with pieces spread all over the world,” said Purdue University’s Jingjing Liang, a co-author on the study and coordinator of the Global Forest Biodiversity Initiative, in a press release.

“I think this work hopefully helps us understand the urgency of what we’re doing, and will help us make changes that we actually already know how to make in terms of how we use energy, how we make energy, how we go about growing our food, how we live on the planet,” said Reich.

“We can make those changes because we already know that these changes can be done in a way that is economically neutral or beneficial.”

This story has been updated to note where the study was published.

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