A study by an international team of researchers says that there are 3.04 trillion trees on Earth, roughly 422 trees per person. That number is about 7 times greater than previous estimates.But according to the study, published in the journal Nature on September 2, 2015, the number of trees has dropped by 46% almost half since the onset of agriculture about 12,000 years ago. Thomas Crowther, a Yale University Climate & Energy Institute postdoctoral fellow is lead author of the study. Crowther said: [Trees] store huge amounts of carbon, are essential for the cycling of nutrients, for water and air quality, and for countless human services. Yet you ask people to estimate, within an order of magnitude, how many trees there are and they don’t know where to begin. I don’t know what I would have guessed, but I was certainly surprised to find that we were talking about trillions.