The good news there are about 422 trees for every person on Earth - eight times more than previously estimated. The bad news is that the number is falling by 15 billion trees every year.
Since human civilisation began. In that time, tree cover of the planet has nearly halved, scientists estimate.
A multi-national team of researchers led by Yale University has estimated there are about three trillion trees on Earth. They arrived at the number by both physically counting trees as well as supercomputer analysis of satellite imagery.
The research was reported in Nature.
"I don't know what I would have guessed, but I was certainly surprised to find that we were talking about trillions," the study's lead author Thomas Crowther of the Yale School of Forestry and Environmental Studies in Connecticut, told ABC news.
"The highest densities of trees were found in the boreal forests in the sub-arctic regions of Russia, Scandinavia and North America," the researchers say. "But the largest forest areas, by far, are in the tropics, which are home to about 43% of the world's trees."