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How many trees on Earth?

by William (Ned) Friedman, Director of the Arnold Arboretum
September 7, 2015

Arboretum Explorer image by Ned Friedman

How many trees on Earth?

Arboretum Explorer image by Ned Friedman
Here is a simple question: How many accessioned trees are there at the Arnold Arboretum? Well, somewhere around 15,000. I would have to check in with the Curation and Plant Records Department to get a precise number as of this week.

Here is a slightly more complicated question: How many trees are there at the Arnold Arboretum? Well, now we have to think about all of the trees growing at the Arnold Arboretum that are not part of our formal accessioned living collections. This would include a sizable number of trees in the Bussey Brook Meadow, as well as most of the trees in naturalized areas such as the Central Woodland, Peters Hill Woodland, and North Woods. I won’t hazard a guess, but if we needed to know the answer, we could go out there and count.

Now, for a profoundly difficult question to answer: How many trees are there on Earth? In the most recent issue of Nature Magazine, one of the most eminent scientific journals, a group of scholars from around the world have worked very hard to come up with an estimate. The answer is over three trillion trees! (Less than 20% of this total can be found in temperate regions of the world.) No doubt, that is a lot. But what is most chilling about these estimates is that this is only roughly half the number that were present prior to human “civilization.” 

Every year, a net of 15.3 billion trees are disappearing from our planet and my back of the envelope calculations indicate that this works out to 41.9 million lost trees per day, 1.75 million per hour or 29.1 thousand per minute. In other words, it takes humans only 30 seconds to wipe the equivalent of our entire accessioned collection of trees at the Arboretum from the face of the earth. Sobering.

Watch a short video piece on this article.

-Ned Friedman, Director of the Arnold Arboretum

 

 

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