Seven Times More Trees in World than Previous Estimate

(p. A9) There are slightly more than three trillion trees in the world, a figure that dwarfs previous estimates, according to the most comprehensive census yet of global forestation.
Using satellite imagery as well as ground-based measurements from around the world, a team led by researchers at Yale University created the first globally comprehensive map of tree density. Their findings were published in the journal Nature on Wednesday.
A previous study that drew on satellite imagery estimated that the total number of trees was about 400 billion. The new estimate of 3.04 trillion is multiple times that number, bringing the ratio of trees per person to 422 to 1.
. . .
The map was generated using 429,775 ground-based measurements in more than 50 countries, collected from a variety of sources, including the Smithsonian Tropical Research Institute, the National Forest Inventory and several peer-reviewed studies, said Henry Glick, co-director of the Ucross High Plains Stewardship Initiative, a research program within the Yale School of Forestry and Environmental Studies.
The effort paired existing tree-count data, in which a person either counted or estimated the number of trees in a given area, with environmental characteristics such as temperature and elevation. This enabled them to get a more accurate count than the rough forest-cover estimates via satellite. To fill in the gaps where there were no field measurements, they made estimates based on tree-density trends in regions with similar environmental characteristics, Mr. Glick said.

For the full story, see:
MARK ARMAO. “World Has Many More Trees Than Previously Thought, New Report Says.” The Wall Street Journal (Thurs., Sept. 3, 2015): A9.
(Note: ellipsis added.)
(Note: the online version of the article has the title “World Has Many More Trees Than Previously Thought, New Report Says.”)

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