Three Trillion Trees on Earth are More Than Expected, But Still in Decline (VIDEO)

First Posted: Sep 03, 2015 07:19 AM EDT

It turns out that there are far more trees on Earth than previously realized. A new study estimates that there are more than 3 trillion trees on Earth, which is about seven and a half times more than previous estimates. However, the total number has plummeted by 46 percent since the start of human civilization.

So how exactly do you count all of the trees on Earth? It's with the help of satellite imagery, forest inventories, and supercomputer technologies. Using these aspects, the team was able to map tree populations worldwide at a square-kilometer level.

"Trees are among the most prominent and critical organisms on Earth, yet we only recently beginning to comprehend their global extent and distribution," said Thomas Crowther, lead author of the new study, in a news release. "They store huge amounts of carbon, are essential for the cycling of nutrients, for water and air quality, and for countless human services. Yet you ask people to estimate, within an order of magnitude, how many trees there are and they don't know where to begin. I don't know what I would have guessed, but I was certainly surprised to find that we were talking about trillions."

Before this study, there was only a global estimate of 400 billion trees worldwide, or about 61 trees for every person on Earth. Now, the researchers have found that there are about 3.04 trillion trees, which is roughly 422 trees per person.

The highest densities of trees were found in the boreal forests of the sub-arctic regions of Russia, Scandinavia and North America. The largest forest areas, though, were in the tropics, which were home to about 43 percent of the world's trees.

The researchers found that human activity is also the largest driver of tree numbers worldwide. While the negative impact of human activity on natural ecosystems is clearly visible in small areas, this latest study provides a new measure of the scale of anthropogenic effects, highlighting how historical land use decisions have shaped natural ecosystems on a global scale.

The findings are published in the journal Nature.