A shepherd wanders around Lake Urmia in search of meadows for his goats. The desertification of the lake makes it harder each year for farmers to find fertile soil.The dry bed of the lake is a source of salty dust that can be whipped up by strong winds into a dust storm.Iran's Lake Urmia was once the second-largest saltwater lake in the world, covering more than 2,000 square miles at its deepest in the 1990s. In the past two decades, the lake has dried out, shrinking at times to less than 20% of its average size. It's not a story of climate change, though that certainly contributed.