Earlier this month, researchers announced they had found a new, more accurate way to count all the trees in the world.
The last global estimate for the number of trees was 400 billion, which was tallied using mainly satellite imagery.
But researchers have a new estimate, and it’s a little higher than the old one.
Specifically, about 7.5 times higher.
There are actually about 3 trillion trees on the planet, according to a paper published in the journal Nature, which noted that that’s still roughly half as many as there were at the dawn of civilization. Researchers counted the trees by combining satellite images with on-the-ground tallies.
Maine — the most heavily forested state in the nation — employs a similar method to estimate its number of trees.
According to Ken Laustsen, the Maine Forest Service’s biometrician who oversees the annual tree-counting effort, Maine tallies its trees by sampling about 3,500 plots around the state.
Teams of two annually visit 700 of those 1/24-acre plots and count the trees. Then they use aerial photographs to expand that count to surrounding regions.
Based on 2014 data, there are 24.3 billion trees in the state. But if you limit that to the parameters of the recent global count (trees that are at least 4 inches in diameter) the number drops to 5 billion, Laustsen said. And the number of trees that are merchantable — or constitute harvestable timber — is 3.2 billion, he said.
“I have a lot of confidence in the data that’s collected in Maine through this [USDA Forest Service Forest Inventory and Analysis] program,” said Laustsen. “Data has been collected in Maine since 1958, so we have a long history of data on our forest resources.”
Knowing the number of trees is important in a state whose forestry industry brings in around $8 billion, he said. And since trees consume carbon dioxide, it’s good to know how many are helping to reduce greenhouse gases.
