North Korea is notoriously sealed off from the rest of the world, but satellites still provide glimpses of physical events that occur there. In April, for example, NASA's 14-year-old Aqua satellite, whose mission is to collect information about the Earth's water cycle, used its Moderate Resolution Imaging Spectroradiometer to observe dozens of forest fires spewing smoke that spread over the southeastern corner of the totalitarian nation. Here's a satellite image from NASA's website.
The same satellite has captured images of other, smaller forest fires in North Korea in 2005, 2009 and 2011.
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NASA says that some of the fires may have been set deliberately by farmers to clear land, because they're along agricultural areas, but others appear to be wildfires, possibly caused by drooping, aging power lines. A subsequent image produced in early May shows scarring from the fires.
Fires are just one of the problems endangering North Korea's forests, according to a 2009 article in Asia-Pacific Journal by environmental activist Peter Hayes, who actually has visited the country. Hayes writes that North Korea's problems with deforestation date back to over-cutting by Japanese colonists when that country controlled Korea in the early 1900s.