More than three trillion trees exist on Earth – roughly 422 per person – but the total number of trees has plummeted by 46% since the start of human civilisation, a Yale-led study said.
The new estimate of more than 3 trillion trees on Earth is about seven and a half times more than some previous estimate of 400 billion.
An international team of researchers mapped tree populations worldwide at the square-kilometre level using a combination of satellite imagery, forest inventories, and supercomputer technologies.
“Trees are among the most prominent and critical organisms on Earth, yet we are only recently beginning to comprehend their global extent and distribution,” said Thomas Crowther, a postdoctoral fellow at the Yale School of Forestry & Environmental Studies (F&ES) and lead author of the study.
The study was inspired by a request by Plant for the Planet, a global youth initiative that leads the United Nations Environment Programme’s ‘Billion Tree Campaign'.
At the time, the only global estimate was just over 400 billion trees worldwide, or about 61 trees for every person on Earth. That prediction was generated using satellite imagery and estimates of forest area, but did not incorporate any information from the ground.
Crowther and his colleagues collected tree density information from more than 400,000 forest plots around the world. This included information from several national forest inventories and peer-reviewed studies, each of which included tree counts that had been verified at the ground level.