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Phoenix666 [soylentnews.org] writes:

Talk about mighty oaks growing from little acorns [phys.org]! A 9-year-old's homework assignment has led to the world's most comprehensive tree-counting project, which in turn stands to increase the value of upcoming missions from NASA and other space agencies.

Felix Finkbeiner was a fourth-grade student in Bavaria in 2007 when his teacher assigned a classroom presentation on climate change. His research brought him to the story of Wangari Maathai of Kenya, the first African woman to be awarded the Nobel Peace Prize. Among other accomplishments, she started a grassroots movement to counter deforestation and inspired the United Nations Environment Programme's Billion Tree Campaign.

Felix challenged his classmates—and ultimately, children throughout the world—to plant a million trees in each country, an idea that grew into an international youth organization called "Plant-for-the-Planet." In 2011, the UNEP turned its Billion Tree Campaign over to the organization Felix had started. By that time, the UN program had celebrated the planting of 12 billion trees.

Twelve billion trees is a lot, but how much does it increase the world's tree population? By a few percent? By half? No one knew. Enter Tom Crowther, then a postdoc at Yale.

"My friend worked for Plant-for-the-Planet," Crowther said. "The problem they were having was that they didn't know what contribution they were making because they didn't know how many trees there were to start with. So I planned to spend a couple of months digging around, doing a few quick calculations, just so they could have some idea of the total number, at least to within an order of magnitude."

But that relatively modest task quickly grew in scope. "So many people were interested and I managed to gather so much more data than we initially expected, it just snowballed," Crowther said. The result was a study published last September in the prestigious journal Nature, which sparked headlines in the general press declaring that Earth is home to 3 trillion trees, nearly eight times as many as what Crowther's paper cites as the previous best estimate. That's using the American definition, by the way, in which one thousand billion equals one trillion.

Crowther and his colleagues generated the first global tree map of its kind by coupling some 430,000 ground-based measurements of forest density, from every continent except Antarctica, with data from NASA's Moderate Resolution Imaging Spectrometer (MODIS) instruments onboard the Terra and Aqua satellites.

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