Saving the trees, we are not. An unprecedented global map of forest changes over the last decade shows that deforestation is still rampant globally.

Between 2000 and 2012, the world lost 2.3 million square kilometers of forest–roughly equivalent to the entire U.S. east of the Mississippi–while it only gained 800,000 square kilometers, the study, reported yesterday in the journal Science, shows.





The work was a four-year collaboration of scientists from NASA, Google, the U.S. Geological Survey, and the University of Maryland, and provides a first-ever detailed look at changes in the forest across the globe, whether they are due to logging, fire, disease, or storms.

“I think what we are witnessing today is one of those breakthrough moments in conservation,” says Guillermo Castilleja, environmental conservation program officer with the Gordon and Betty Moore Foundation, which sponsored the work. “Before today,” he said on a press call with reporters, “if you wanted to compare deforestation trends in different parts of the world, you’d have to conduct separate studies.” Importantly, it is based on objective imagery, rather than self-reported data by each country that can vary widely–as many other assessments have used in the past.

The map was possible for the first time because the U.S. government only made imagery from its Landsat satellite program available for free to researchers for the first time in 2008. Before, they would have had to pay image-by-image. Another problem was the lack of computing power.

To create the map, the team looked at more than 650,000 satellite images obtained between 1999 and 2012, and analyzed 20 trillion pixels using Google Earth Engine–a high-performance geospatial data processing platform that used 10,000 parallel computers in Google’s data centers to complete in a few days what would have taken a single computer 15 years to do. Now they plan to update the map every year.





“The product is globally consistent and locally relevant,” says Matthew Hansen, the University of Maryland geographical sciences professor who led the 15-person team. “Less formally speaking, we think this map is cool. … You can see the amazing variety of dynamics.” For example, the maps show the effects of forest fires in Russia and logging in Indonesia.