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.
VIDEO: Should We Control Wildfires?
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.
BLOG: Google Maps North Korea
In the mid-1990s, the forests suffered even more harm when the government ordered farmers to cut down trees on steep slopes and plant crops in those areas to help alleviate chronic famine. After that, flooding carried away the topsoil in many of those areas, making it difficult to replace the forests. Acid rain and pollution from neighboring China also has taken a toll upon North Korea's trees. A UN report released in 2013 concluded that North Korean forests shrank by 31 percent between 1990 and 2010.
Photo: NASA Earth Observatory