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.
There were bright spots and troubled ones around the world. Brazil, which used to be responsible for half of the world’s deforestation, has reversed course and now is the most improved country by far. Indonesia, on the other hand, had the largest increase in forest loss—more than doubling its annual rates over the decade-long period. Paraguay, Malaysia, and Cambodia had the highest overall rates of forest loss.
The United States is not without its own problems. Subtropical forest, like those of the Southeastern United States, actually lost tree cover at a faster rate than rainforests due to intensive tree harvesting. Over the study period, an astounding one-third of the U.S southeastern forest cover changed, either being lost or regrown.
The map could will have plenty of applications to help conservation researchers, environmentalists, and maybe even the logging industry going forward. For example, in helping monitor whether nations are complying with their commitments to a U.N. climate or conservation agreement, and helping understand how policy changes in one nation might affects deforestation in the rest of the world.
Rebecca Moore, of Google, said the company was committed to providing additional computing resources for further research. With the scale required to complete the job, "you can see why there never has been a global forest map produced in high resolution before," she said.