The tree census.

• Position: ENVIRONMENT - Brief article

How many trees are there in the world? Until now, scientists could only guess. But using satellite images and on-site counting in more than 50 countries, researchers at Yale University in Connecticut tallied more than 3 trillion trees in the world--roughly seven times more than previously thought. The "tree census" found 228 billion trees in the U.S., ranking it fourth after Russia, Canada, and Brazil. Despite the good news, researchers warn that the number of trees on Earth has fallen by 46 percent since the start of civilization. Due to demand for timber and...