There is good and bad news about trees on our planet. The good news is that there are seven times more than we thought. Scientists estimated that the world had 400 billion trees. A new study says we have three trillion trees. That's a three followed by 12 zeroes. There are over 420 trees for every person alive today. A researcher said: "It's not good news for the world or bad news that we've produced this new number."

The bad news is that the earth once had six trillion trees. Humans have cut that number in half. Europe used to be a giant forest. Now much of it is fields and cities. We are responsible for the loss of three trillion trees. Another 15 billion trees are lost each year. Scientists said this number is a lot higher than 100 years ago. The researcher warned that we must try harder to bring back healthy forests worldwide.