Using Landsat imagery and cloud computing, researchers mapped forest cover worldwide as well as forest loss and gain. Over 12 years, 888,000 square miles of forest were lost, and 309,000 square miles regrew.
In this era of big data, anyone can now see how and where the world's forests are changing thanks to a new mapping project made possible, in part, by the computing resources of the tech giant Google.
The map compiles 100-foot-resolution satellite images of Earth's land area taken each season, every year between 2000 and 2012, to paint a picture of where trees were lost or gained. Globally, the map shows that 888,000 square miles of forest were lost between 2000 and 2012. In the same period, 309,000 square miles were gained.
"We've been working on global-scale land cover monitoring for a while but just with big, blurry pixels. This is the first time we've done it with a resolution and granularity where change is quite discrete and we can quantify it clearly," Matthew Hansen, a remote sensing scientist at the University of Maryland who led the team that created of the map, told NBC News.
Since forest areas are logged or burned more or less all at once, but they grow back slowly over years or decades, areas of loss and gain are rarely in the same place in the time series, noted Hansen. Rather, the gains come in reforested lands that were cleared before 2000, or on abandoned agricultural land such as in Russia.
The map makes clear the location of working forests such as in the southeastern U.S., where 31 percent of the forest cover was either lost or regrown over the time series. Same goes for northern Europe.
"If you look at Finland and Sweden, it is patches of loss-gain, loss-gain, loss-gain, across the whole country, which is just IKEA on the landscape — it is a forestry culture," Hansen said.
Global view of problems ... and fixes
Applications for the new global forest map range from calculating how much carbon is stored in the world's forests to identifying what countries are logging trees most ravenously. "Whether you are a tree hugger or a logger, this map could be useful to you," Hansen noted.
The map does bring a new level of transparency to forestry accounting, he added. It opens up for the world to see the impact of Brazil's conservation policy, for instance, where the rate of forest loss was halved to 8,000 square miles a year over the course of the decade.
The map also shows that Brazil's deforestation reduction is more than offset by increased forest loss in places such as Indonesia, Malaysia, Paraguay and Bolivia. Overall, the forest loss in the tropics is increasing by 811 square miles a year, according to Hansen and colleagues, who discuss the map in a paper published today in the journal Science.
"Observing the planet at the Landsat scale — one pixel resolution is 30 meters or 100 feet — is really where the action is ... that's the management scale, that's where fires are, etc.," Josef Kellndorfer, a senior scientist at the Woods Hole Research Center in Falmouth, Mass., who is an expert in remote sensing, told NBC News. He wasn't involved with map project, but is familiar with Hansen's work.
"Understanding those kinds of forest dynamics will hopefully allow us to be sharper" about making better policies that can reverse trends in deforestation, he added.
This may enable the United Nations Food and Agriculture Organization, based in Rome, to further its goal of making forestry more sustainable and productive, according to Erik Lindquist, a forestry officer who works in remote sensing for the organization.
Lindquist says that the value of the map is that it's "globally consistent," but can be looked at for local relevance.
How to make a map
For the project, Hansen and colleagues accessed high-resolution satellite imagery from the U.S. Geological Survey's Landsat 7 satellite, the first in the decades-long remote sensing data collection program to capture imagery from Earth's entire land area. This data was made freely available in 2008, which removed a cost barrier for this type of mapping work that researchers had previously found insurmountable.
The other piece to the puzzle was the ability to process the more than 650,000 images in a streamlined fashion. Enter tech giant Google's cloud computing resources. The company's Earth Engine crunched the data in matter days. "On a single computer, it would have taken 15 years," Hansen noted.
Going forward, he said, the database will be updated annually.
John Roach is a contributing writer for NBC News. To learn more about him, visit his website.
First published November 14 2013, 11:14 AM