Curiosity 1 of 10
1. There are more trees on Earth than stars in the Milky Way
A survey published in 2015 estimated that Earth has about 3 trillion trees. The Milky Way, our galaxy, has between 100 and 400 billion stars.
How the number of trees in the world is estimated
No one counted tree by tree. The estimate, published in the journal Nature by a team led by Yale University, combined ground measurements taken in more than 400,000 forest areas with satellite images and climate and terrain data.
The number was surprising: it was about eight times higher than the previous estimate, which was around 400 billion. Divided by the population, that gives a few hundred trees per person.
The same study calculated that humanity cuts down about 15 billion trees a year, and that the number of trees on the planet has fallen by about 46% since the beginning of agriculture.
The largest concentrations are in tropical forests, such as the Amazon, which alone has hundreds of billions of trees, and in the cold northern forests of pines and firs, in Russia, Scandinavia and Canada.
Did you know? The stars of the Milky Way are hard to count because many are hidden behind clouds of dust. That is why estimates vary so much, from 100 to 400 billion.
About this list: these are 10 curiosities about planet Earth, one per page, with an explanation of each and an extra detail in the "Did you know?" box. The sources are at the end of the list.
