This beautiful satellite image shows one of the most saddening long-term natural disasters on Earth. The black patch in the upper left corner is the remaining body of the Aral Sea, located on the border between Kazakhstan and Uzbekistan in Central Asia—which has lost around 90 percent of its water volume since 1960 because of Soviet-era irrigation schemes.
Once, it was the world's fourth-largest inland water body; now it is a dry, white salt terrain called the Aral Karakum Desert, where violent sandstorms pick up salt, sand, and chemicals from former weapons testing, industrial projects and fertiliser runoff. It's carried across hundreds of kilometers, causing severe health problems for the local population and making regional winters colder and summers hotter. In addition, the area's fishing industry has been devastated.
What do we see exactly in the striking image above? The European Space Agency explains:
This multitemporal radar image was created by combining three radar scans from satellite Sentinel-1A, assigning each a colour: red (from 17 October 2014), green (from 28 December 2014) and blue (from 14 February 2015). Different colours represent changes between the acquisitions.
In the lower right, the red, yellow and green boomerang shape shows where water flows into the dry seabed from a river, and colours show how the area covered in water increased over time.
Along the left side of the image, the large dark area shows where water is still present. Colours along the water's edge show water-level changes between acquisitions. Red shows a lower level than blue, so the water level was lower on 17 October 2014 than on 14 February 2015.
Zooming in on the lower-left corner, we can see the straight line of a road outside of the seabed, with white dots showing where the radar signal has reflected off of human-made structures. White dots also appear further east, showing where structures have been built in the seabed.