A billion trees sounded like a lot. That would let scientists do a more direct census of trees over and over, to track how the total number changes.
“They want to generate forests on a global scale”, says Crowther.
The study said that experts had previously estimated there were 400 billion trees globally, but said this does not mean there are more trees now.
But satellites can only “see” trees from above. The results show sharply different tree-per-person ratios around the world.
That prediction was generated using satellite imagery.
Using this method, researchers estimate that there are actually 3.04tn trees on our planet today – or 422 per person.
But there was bad news, the researchers reported in the journal Nature. In contrast, boreal forests contained 0.74 trillion trees, and temperate regions had 0.61 trillion. The new estimate is three trillion large trees. “I assumed that this was somewhere out there, it’s information that someone will know”, says Crowther.
“To me it is more the first robust estimate of the number of trees”.
Thus, the Yale University specialists say that, when compared to the dawn of modern civilization, Earth’s tree population has dropped by about 46%.
No other factor has had such a profound impact on the world’s stock of trees.
“The message remains that a billion trees is still a huge contribution”, he said. The satellite imaging determined where the forests were located, utilizing no less than 429,775 separate measurements of the density of trees in various locations, and the field-work dove into them to determine how many trees exist in the multitude of forests. This amounts to around 5bn trees per year.
The report also calculates that Louisville might need to spend as much as $1.7 billion on a tree-planting program over 40 years to achieve a goal of covering 45 percent of its 398 square miles that includes all of Jefferson County.
“It is extremely concerning to discover the amount of damage that humans have already had and the terrifying rates at which forests are being depleted”.
Using information from around 400,000 forest plots, the researchers painstakingly crunched a ton of numbers.
“It really highlights how big of an impact humans are having on the Earth at a global scale”, he says.
The new study was triggered by a request from the Billion Tree Campaign.
Scientists undertook the study after a youth group called Plant for the Planet approached Crowther asking for a more accurate estimate of the world’s trees than what was available at the time.
The researchers revealed that approximately 15 billion trees are chopped down each year, adding that human activity is detrimental to tree abundance worldwide.
“I don’t think that our numbers are altering scientists’ perspective of how much carbon is stored in the global forest”.
Though the new figure is remarkably higher than expected, the news is not all bright. [Nature’s Giants: Photos of the Tallest Trees on Earth].
Trees pull carbon dioxide out of the atmosphere as they grow, and cutting or burning them down releases that carbon again. Earth is home to just over 3 trillion trees, but they are being lost at an alarming rate thanks to human activities.
