Eight Times More Trees Than Previously Estimated

A new assessment from Yale University, published in Nature, has found that there could be almost eight times more trees in the world than previously estimated in 2008. Led by Dr Thomas Crowther, the team collected information about tree density from more than 400,000 forests around the world. Their data also included national forest inventories and studies in which the trees were physically counted. Collating all of this information, the team was able to build a better idea of what could be seen in satellite pictures. These pictures are very good at showing the extent of forest, but not at revealing how many trees are actually standing beneath the canopy. So, instead of there being only about 400 billion trees in the world, there are actually an estimated three trillion. This is a whopping 7.5 times more than thought, and means there are around 420 trees for every person on the planet. According to the study authors, more than a third of the world's trees are located in the tropics and subtropics. The greatest density of trees can be seen in the boreal forests, just below the Arctic, where there are about 0.7 trillion trees. Around 0.6 trillion trees can be found in temperate climates, between these two regions. This more refined number will become the baseline figure so that other research can become more accurate. For example, experts will be able to get a better idea of the biodiversity in plant and animal habitats. It also means new models of the climate can be developed because of the vastly important role that trees play in removing greenhouse gases from the atmosphere. The team did point out, however, that it was now clear the influence humans have had on the planet's tree population. They explained that we remove about 15 billion trees every year, but only replant around five billion. This means that despite it being great news that there are so many more trees in the world than we thought, we do still have to take better care of them so we don't wipe them out altogether. "Trees store huge amounts of carbon, are essential for the cycling of nutrients, for water and air quality, and for countless human services," explained Dr Crowther. He said that in spite all of this, it is still very difficult to estimate just how many trees there are and even he was surprised to find they numbered in the trillions. But the team is being understandably careful with the information. "It's not good news for the world or bad news that we've produced this new number," Dr Crowther added. "We are simply describing the state of the global forest system in numbers that people can understand."