A new study released Wednesday in Nature Magazine finds that the Earth’s tree population is seven times higher than previously thought. But the rate of deforestation is also higher as well.
The study’s main author is Thomas Crowther, postdoctoral researcher at Yale University, who led a team of 38 scientists. The previous estimate of 400 billion living trees proved to be wildly inaccurate, the most probable tally given by the new study rising the figure to 3.04 trillion.
Surprisingly, given the vital role trees play in the environment, the old figure was the result of a rough estimate.
“Trees are among the most prominent and critical organisms on Earth, yet we are only recently beginning to comprehend their global extent and distribution,”
Crowther was quoted as saying regarding the importance of his work.
In this new study, scientists combined two methods of sampling trees in order to ensure the most accuracy. Forested areas where delimitated by satellite observation, and the tree density of any given type of forest was assessed by teams on the ground. This double approach was impossible until recently.
While the tree population is seven times higher than previously thought, the number of trees is actually the lowest it’s ever been since humans started to developed agriculture, 12000 years ago. According to scientists, it only constitutes 46% of what the tree population would be without human intervention. Crowther calls this difference “astronomical”.
Forests are by far the biggest “reducers” of carbon dioxide in the atmosphere, which is one of the gasses scientists find responsible for the changes in weather recorded in the last decades.
The paper finds the number of trees to be in constant decline, at a rate of 10 billion per years. While forest fires and pest outbreaks also take their share of trees, the annual reduction is mostly due to human intervention. The paper finds a reverse correlation between human density and the expanse of forests, with the most densely populated nations exhibiting the lowest degree of forestation.
The highest density of trees was recorded in the boreal forests, the largely uninhabited northern part of the globe. It alone houses a quarter of the world total tree population. However, among the regions of the globe, the tropics are the most extensively forested, with 43% of the Earth’s forested area to be found here.
According to Crowther, the knowledge gathered by his team reflects to other areas of biology and ecology. Among others, it could be instrumental in aiding preservation efforts, since a lot of species are dependent on the density of trees in their habitat.
Photo Credits: en.wikipedia.org