As of yesterday, we now know (roughly) how many trees there are on Earth — about 3.04 TRILLION! If that seems like a lot or a little or if you actually have no idea how many trees you thought were on Earth, consider this: Scientists used to think that the number was around 400 BILLION. And if they’re that far off on tree count, imagine how wrong they are about climate change! Kidding, kidding. Relax, everyone.

The previous estimate was so low because it was based solely on satellite images from space. The new and improved estimate combines satellite data with more than 429,775 on-ground measurements, the AP reports. Why would someone suddenly take the time to count how many trees were on Earth, you ask? Funny story:

According to the AP, this all started when a group of kids decided to plant 1 billion trees in order to combat climate change. They asked Thomas Crowther of Yale’s School of Forestry and Environmental Studies if doing so would actually make a difference, and Crowther was like, “Huh … I don’t know. How many trees are there on Earth, anyway?”

Fast forward two years, and Crowther and his colleagues have published a study in Nature reporting the new estimate (watch the cool video above for more on their research).

That there are so many CO2-capturing trees on this devastatingly polluted space sphere may sound like good news, but things look a little less rosy when you consider what Earth used to look like. Here’s more from the AP:

“These things really dominate our planet,” Crowther said. “They are the most prominent organisms on our planet and there are 3 trillion of them.”

But Earth used to be covered with far more trees. Using computer models, Crowther and colleagues estimated that before human civilization Earth had about 5.6 trillion trees. So the number of trees on Earth has been chopped nearly in half.

Crowther mostly blames people. His study found that 15 billion trees are cut down each year by people, with another 5 billion trees replanted. That’s a net loss of 10 billion trees a year. At that rate, all of Earth’s trees will be gone in about 300 years.

“Humans are diminishing that huge population on such a global scale,” Crowther said.

Nearly 1.4 trillion of Earth’s trees are in tropical and subtropical forests, but that’s also where the rate of forest loss is the highest, the study found.

On the plus side, at least now Crowther can finally go back to those earnest youngsters and say: “No, children — your efforts will not make a difference. Life is full of disappointments that way.” And those almost-activists can go on to become the apathetic teens their hormones so desperately want them to be.