How Many Trees Are There?

How many trees are there in the world? Scientists are making progress in the effort to answer this question.

An article in the Washington Post highlights a study recently published in Nature. A team of 38 scientists reported their research on not just the number of trees, but the distribution and, most importantly, how this count has been changing in recent years.

The investigation combined satellite observation data with more than 400,000 ground-based observations of tree density. It turns out that nearly half the planet's trees are in tropical regions, with most of the rest about equally divided between temperate zone and boreal (northern) forests. For those who may be wondering, the scientists' definition of “tree” is a woody plant with trunk diameter at chest height of at least 100 cm, or about 4 inches.

The bottom line looks like good news. The study found that there are more than three trillion trees, which works out to 422 trees per person on the planet. This is more than seven times the previous estimate of 400 billion.

How do different nations stack up as far as trees per person? Canada, with its extensive boreal and tundra forests and relatively low population density, has an impressive 8,953 per person, and for similar reasons Russia racks up 4,461. This outdoes Brazil, which with its rapidly disappearing Amazon rain forest is down to 1,494 per person. At 716, the U. S. is comfortably above the world average. China has only 102 per person, and crowded India only 28. My Indian friends would counter that measured by resource consumption, the average American counts as dozens of average Indians. Could be they have a point there.

Three trillion is a lot of trees, but the scientists believe the tree count has fallen 46% since the beginning of human civilization. And the current annual net loss from human activity, wildfires, and pest outbreaks is around 10 billion. A sobering flip side to the increased count is that restoring forests to historic levels would require many more trees than previously thought.

Yet another reason to plant more fruit trees.