Thereis good and bad news about the number of trees on our planet. The good news isthat there are seven times more trees than we thought. A few years ago,scientists believed that the world had 400 billion trees. However, a new studyfrom Yale University shows that there are around three trillion (万亿) trees. That's athree followed by 12 zeroes. That means there are about 420 trees for everyonein the world today.

    Thebad news is that thousands of years ago, the earth had six trillion trees.Humans cut down half the number of trees on the planet. Take Europe forexample, it was a large forest thousands of years ago. Now much of it is citiesand towns. And another 15 billion trees are lost each year.

    DrThomas Crowther is one of the scientists from Yale University. He said the newnumber of trees from their study would change nothing. "The study onlyshows we need to do more to protect our forests," he said.