From NASA, with a massive version of the image available at the link, a map of climate change-spawned vegetation changes compiled from satellite images captured between 1984 and 2012, with green pixels indicated increased vegetation growth and brown pixels indicating diminished growth:
The story, from NASA:
The northern reaches of North America are getting greener, according to a NASA study that provides the most detailed look yet at plant life across Alaska and Canada. In a changing climate, almost a third of the land cover – much of it Arctic tundra – is looking more like landscapes found in warmer ecosystems.
With 87,000 images taken from Landsat satellites, converted into data that reflects the amount of healthy vegetation on the ground, the researchers found that western Alaska, Quebec and other regions became greener between 1984 and 2012. The new Landsat study further supports previous work that has shown changing vegetation in Arctic and boreal North America.
Landsat is a joint NASA/U.S. Geological Survey program that provides the longest continuous space-based record of Earth’s land vegetation in existence.
Previous surveys of the vegetation had taken a big-picture view of the region using coarse-resolution satellite sensors. To get a more detailed picture of the 4.1 million square-mile area, scientists used the Landsat 5 and Landsat 7 satellites.
Landsat, like other satellite missions, can use the amount of visible and near-infrared light reflected by the green, leafy vegetation of grasses, shrubs and trees to characterize the vegetation. Then, with computer programs that track each individual pixel of data over time, researchers can see if an area is greening – if more vegetation is growing, or if individual plants are getting larger and leafier. If, however, the vegetation becomes sparser, the scientists would classify that area as browning.
Researchers have used similar techniques to study Arctic and northern vegetation with other satellite instruments, such as the Advanced Very High Resolution Radiometer (AVHRR). But Landsat can see smaller differences across a landscape – it takes one measurement for each 30-by-30 meter (98-by-98 foot) parcel of land, which is about the size of a baseball diamond. AVHRR collected one measurement for each 4-by-4 kilometer (2.5-by-2.5 mile) area.
“We can see more detail with Landsat, and we can see the trend more reliably,” Ju said. With finer-resolution and better calibrated data from Landsat, the researchers were able to mask out areas that burned, or are covered in water, to focus on vegetation changes. The more detailed look – now available to other researchers as well – will also let scientists see if a correlation exists between habitat characteristics and greening or browning trends.