On a recent visit to the Gobi desert, which stretches across China’s western Gansu province, I came upon an unusual sign. In the midst of a dry, sandy expanse stood a large billboard depicting a settlement the government intended to build nearby — white buildings surrounded by lush, green, landscaped lawns, and in the center a vast, gleaming blue reservoir. The illustration’s bright colors were quite unlike the actual surroundings, which consisted of dull sky that faded into a horizon of undulating, parched-brown hillsides.