The Earth has 3 trillion Trees...Study Finds

The good news: A new study finds that there are 3.04
trillion trees on Earth, 7½ times more than previous
estimates.
That's more than 3,000,000,000,000. A whopping 12
zeros. Roughly 422 trees -- a tiny forest! -- for every
person on the planet.
The bad news? Researchers estimate that the total
number of trees has plummeted by roughly 46%
since the dawn of human civilization. And we're
mostly to blame.

An international team of researchers employed
satellite imagery, forest inventories and
supercomputer technologies to map tree populations
worldwide at the square-kilometer level. The
resulting study, led by scholars at Yale University,
was published this week in the journal Nature (PDF).
Researchers from 15 countries collaborated on the
study. They say it's the most comprehensive
inventory of tree populations ever produced.
"Trees are among the most prominent and critical
organisms on Earth, yet we are only recently
beginning to comprehend their global extent and
distribution," said Thomas Crowther, a postdoctoral
fellow at the Yale School of Forestry and
Environmental Studies and lead author of the study.
"They store huge amounts of carbon, are essential
for the cycling of nutrients, for water and air quality,
and for countless human services," Crowther said in
a statement provided by Yale. "Yet you ask people to
estimate, within an order of magnitude, how many
trees there are and they don't know where to begin. I
don't know what I would have guessed, but I was
certainly surprised to find that we were talking about
trillions."
The study was inspired by a request two years ago by
Plant for the Planet, a global youth initiative that
plants trees to reduce the effects of climate change.
At the time, the only global estimate was about 400
billion trees worldwide, according to Yale -- or about
61 trees for every person on Earth.
Scientists made that prediction by using satellite
imagery and estimates of forest area but did not
incorporate any information from the ground.
Crowther and his colleagues also collected tree-
density information through national forest
inventories and peer-reviewed studies that included
tree counts verified at the ground level.
The highest densities of trees were found in boreal
forests in the sub-arctic regions of Russia,
Scandinavia and North America. But the largest
forest areas are in the tropics, which are home to
about 43% of the world's trees.


Researchers hope their findings will inform scientists
about the structure of forest ecosystems in different
regions and help improve predictions about carbon
storage and biodiversity around the world.
But the study also serves as a warning about how
human effects -- such as clearing forests to build
subdivisions -- decimate the world's tree population.
Deforestation, land development and forest-
management decisions are responsible for a gross
loss of over 15 billion trees each year, reported the
study, which noted that tree densities usually
plummet as the human population increases.
"We've nearly halved the number of trees on the
planet, and we've seen the impacts on climate and
human health as a result," Crowther said. "This study
highlights how much more effort is needed if we are
to restore healthy forests worldwide."