The browns and tans in this image signify the sand dunes and stone plateaus of the Sahara in Northwest Africa.The Sahara, which means "desert" in Arabic, is the world's second largest desert (after Antarctica) spanning 9 million square kilometers (3.5 million square miles).
The Sahara is of course very hot and dry, with a mean annual temperature of about 30 degrees Celsius (86 degrees Fahrenheit) and mean annual rainfall of 25 millimeters (less than an inch).
But what makes this environmental one of the harshest on the planet is its variability: temperature can fluctuate by as many as 38 degrees Celsius (100 degrees Fahrenheit) in a single day and the region can receive no rain for years at a time, only to be deluged with a single, large rainfall event.
According to the World Wildlife Fund, the Sahara provides habitat for a surprising number of species, including 70 mammals, 100 reptiles, and 90 birds. These sensitive areas are currently under pressure from agriculture practices that contribute to soil erosion, a process called desertification.
Projects are currently underway to remedy this problem by planting vegetation to keep sand in place and by creating barriers to block the movement of sand.