Earth is home to 3 trillion trees, according to one of the most comprehensive assessments of global tree populations ever completed, recently published in the journal Nature. The new estimates were arrived at by using extensive satellite imagery combined with ground-based tree density estimates, a method more comprehensive than that used in the past. Because the number was so much higher than the previous estimate of 400 billion trees, the new findings are a small cause for celebration.
The bad news, though, is that the world suffers a net loss of 10 billion trees per year. Even schoolchildren can do the math to figure out how many years it will take at 10 billion a year to reach 3 trillion. The survey estimated that the total number of trees on Earth has fallen by nearly half since the start of human civilization. Of particular concern are forests in sub-Arctic regions, home to about 43 percent of the global tree total, mainly in Russia, Scandinavia and North America.
Conversion of land for agriculture has been the most devastating force on global forests, but industrial and urban development is taking an increasingly large toll. Japan is in some ways the exception, though not entirely. Japan ranks third for percentage of total land area being forested, after Finland and Sweden. Two-thirds of Japan is still covered by forest, double the world average.