COVER More than half of the world’s largest lakes have declined over the past three decades. Human water consumption, warming climate, and sedimentation are largely responsible. Lake Powell, shown here, with its once-submerged walls that now appear as whitened surfaces, exemplifies this drying trend. Nearly one-quarter of the world’s population resides in a basin with a drying lake, which underscores the importance of management solutions. See pages 693 and 743.

Photo: Pete McBride