One Trillon Trees

A new study finds that there is currently room on Earth to reforest an area the size of the
continental U.S. Trees like this Valley Oak sprout have the potential to help sequester massive amounts of carbon. Photos by Suzanne Guldimann

Trees may be the best way to combat climate change. A new study provides conclusive evidence that protecting, conserving, and reestablishing forests by planting at least a trillion trees may be the most cost effective and efficient way to combat climate change. 

The Crowther Lab at ETH Zurich investigates nature-based solutions to climate change. The lab’s most recent findings, published in the journal Science, show that Earth could support nearly 17 million square miles of additional continuous tree cover, an area the size of the U.S.

“We all knew that restoring forests could play a part in tackling climate change, but we didn’t really know how big the impact would be,” stated Thomas Crowther, co-author of the study and founder of the Crowther Lab at ETH Zurich. “Our study shows clearly that forest restoration is the best climate change solution available today. But we must act quickly, as new forests will take decades to mature and achieve their full potential as a source of natural carbon storage.”

The study found that once those trillion trees were mature, the new forests could store nearly two thirds of the carbon that has been released into the atmosphere as a result of human activity since the Industrial Revolution. 

Study lead author Jean-François Bastin explained that “one aspect was of particular importance to us as we did the calculations: we excluded cities or agricultural areas from the total restoration potential as these areas are needed for human life.”

The research has inspired some of the world’s largest conservation organizations to come together to reverse global deforestation. A Trillion Trees is “founded on a vision of a world where tree cover is expanding not shrinking,” an announcement for the new non-profit project states. The goal is to connect the project’s funders—Restore our Planet; Wildlife Conservation Society; World Wildlife Fund; BirdLife—with forest conservation ventures, “to inspire society to protect and restore one trillion trees by 2050.”

It’s one of several international campaigns to reverse climate change with trees.

“By working together, we are leveraging our large networks and decades of experience towards a common goal,” the Trillion Trees website states. “To close the gap between aspirational commitments and the reality on the ground, our dedicated team develops ideas into opportunities and connects them to funding. Our ventures are protecting and restoring forests for the benefit of people, wildlife, and a stable climate, and inspiring sectoral change.”

That’s a big goal, but one that advocates say is achievable. However, the trees need to be the right trees planted in the right places, and the trees can’t do all of the work on their own. Crowther stresses that reforestation won’t work without reducing reliance on oil and cutting carbon emissions. 

Look for trees and reforestation to figure into the 2020 presidential election debate, as Democratic candidates develop and campaign on their plans to address climate change.

To learn more about the Trillion Trees Vision visit For information on the Crowther Lab study, visit

Protecting mature forests like this grove of Sequoias is also essental, according to the study.


Suzanne Guldimann

Suzanne Guldimann is an author, artist, and musician who lives in Malibu and loves the Santa Monica Mountains. She has worked as a journalist reporting on local news and issues for more than a decade, and is the author of nine books of music for the harp. Suzanne's newest book, "Life in Malibu", explores local history and nature. She can be reached at

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