LOS ANGELES: How many trees are there on planet Earth? A new study estimates the number at somewhere around 3.04 trillion. That’s about 400 trees for every person. And while that may seem like a lot, the researchers say that before humans began clearing forests, the Earth was home to nearly twice as many trees. “The number of trees cut down is almost 3 trillion since the start of human civilization” said Thomas Crowther, a postdoctoral fellow at the Yale School of Forestry & Environmental Studies who led the study. “That is an astronomical figure.” The team also estimated that the planet is losing 15 billion trees a year, and replacing only 5 billion of them.