In fact, scientists used to believe that the number of worldwide trees was a whole lot lower. That’s a huge number that looks even more impressive when it’s written out: 3,040,000,000,000.īut what’s more astonishing is that we didn’t have this estimate until recently. Science rules! Follow me and “like” Los Angeles Times Science & Health on Facebook.There are approximately 3.04 trillion trees in the world. “It really highlights how big of an impact humans are having on the Earth on a global scale.” “Human activity came out as the strongest control on tree density across all biomes,” he said. “That’s not insignificant.”Ĭrowther added that one of the most dominant themes of the study is how large an effect humans are having on the tree population on the planet. “If you do the math, the net loss is about one-third of a percent of all trees globally,” said Harry Glick, a post-doctoral student at Yale who also worked on the study. Only 5 billion of them are being replaced. The team used a similar technique to estimate that the planet is losing 15 billion trees a year. “We could then identify how many trees were within this area,” Crowther said. To determine how many trees used to be on the planet, Crowther’s team combined its new map of tree density with predictions from the United Nations Environment Program of where forests used to be based on the climate conditions of the pre-Pleistocene period. Another 24.2% of trees can be found in the boreal and tundra zones of Canada, Russia and northern China, where hearty coniferous trees grow in the densest forests on Earth, and 21.8% are in more temperate parts of the world, including the United States and Europe. For us, the spatial map is more attractive than just the number.”Ĭrowther and his colleagues report that 42.8% of the trees on our planet (1.39 trillion) are located in tropical and subtropical forests. “What matters is where they are distributed and whether they are being pressured by urban development or road development. “It doesn’t matter that there are 3 trillion trees,” he said. Saatchi, who was not involved in the Nature study, said that although estimating the number of trees on the planet is intriguing, the real value of the study for scientists and policymakers is that it lays out where those trees are around the planet. Once the researchers had this ground-based data, they used computer models to predict how many trees would be in a given area where only satellite and climate information was available. The study authors were able to track them down from every continent except Antarctica. The ground-based data mostly came from inventories of national forests in 21 countries in addition to other sources. “And it enables the discovery of relationships between tree density, remote sensing measurements and environmental factors.” “That is truly an amazing amount of field data,” said Marc Simard, a senior scientist in the Radar Science and Engineering section at JPL who was not involved with the study. The new study incorporates satellite imagery, but it also relies on 429,775 ground-based measurements of tree density made by an actual person who counted the number of trees in a given area. “Almost half of what comes out of our car tail pipes and factories gets absorbed by nature and from this half, one-fourth of it goes to trees,” said Sassan Saatchi, who studies the planet’s carbon cycle at NASA’s Jet Propulsion Laboratory in La Cañada Flintridge. One of the most important roles that trees currently play is taking carbon dioxide out of the air and transferring it to living things. Among other things, they create habitat for animals and plants and cycle water and nutrients through ecosystems. Trees serve several crucial functions for the planet. “What we provide is a more detailed understanding of what is going on beneath the surface.” “Satellite images can tell you a lot about the forest area and canopy cover,” Crowther said.