A team of Yale researchers tasked with mapping the forest ecosystem has counted 3 trillion trees on Earth. The number is far more than previous estimates, which counted 400 billion.
Researcher Thomas Crowther from Yale and his colleagues came to the estimate using ground survey data including national forest inventories as well as satellite pictures to map the forest ecosystem.
According to study researchers:
We provide the first spatially continuous map of forest tree density at a global scale. This map reveals that the global number of trees is approximately 3.04 trillion, an order of magnitude higher than the previous estimate. Of these trees, approximately 1.39 trillion exist in tropical and subtropical forests, with 0.74 trillion in boreal regions and 0.61 trillion in temperate regions.
That’s about 420 trees for every person on Earth.
The estimate will help researchers studying plant and animal habitats as well as climate change. It’s well known that trees play an important role in global climate change through the carbon cycle. Using the process of photosynthesis, trees convert atmospheric CO2 into carbon-rich carbohydrates and sugars to feed themselves. Oxygen, which is critical for human respiration, is a byproduct of the process. We depend on trees to pull carbon from the air in order to maintain an atmospheric balance. Without them, the Earth’s atmosphere will trap too much heat on the planet’s surface, causing temperatures to rise.
“So, it’s not good news for the world or bad news that we’ve produced this new number,” Dr. Crowther said to the BBC. “We’re simply describing the state of the global forest system in numbers that people can understand and that scientists can use, and that environmental practitioners or policymakers can understand and use.”
The study also showed humans are having a negative impact on the world’s trees, removing 15 billion trees a year while only replacing around 5 billion.
“The net loss is about a third of a percent of the current number of trees globally,” said co-author Dr Henry Glick. “That doesn’t seem to be an insignificant portion and should probably give us cause for considering the role that deforestation is playing in changing ecosystems.”
We’ve already removed 3 trillion trees since the last Ice Age 11,000 years ago. However, scientists caution that the study numbers could be inaccurate because much of the data was taken in North America and Europe and there’s not enough data coming from the Congo Basin, Australia, India, and China. Dr. Martin Lukac from the University of Reading contends that this new estimate is far off from previous estimates and that there are too many margins of error.
The highest forest density was found in the Boreal forest, the world’s largest land-based biome. The line of forests encircles the planet just below the Arctic. The Boreal forest covers most of Alaska, Canada, Sweden, Finland, Norway, and much of Russia.
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Image of forests from Shuttershock