What Katrina has wrought, four years later

For the survivors, hurricane Katrina lives in memories, photographs, and the empty spaces left by lost friends and objects. Its immediate toll was tragedy. The storm that crashed into New Orleans and the Mississippi Gulf Coast four years ago wreaked a shocking $80 billion in damage and resulted in 1,836 confirmed fatalities. But since then, its overall legacy has broadened and, one hopes, has not been all bad. Count these among the lessons it taught and the changes it spawned: *Volunteers matter a lot in a time of crisis. *FEMA's mission has shifted from a top-down to a bottom-up approach. *New appreciation has emerged of the need to retain and restore wetlands to help absorb storm surges. *Storm-tracking capabilities have advanced in ways that improve public safety. *Hurricanes have moved to the center of the climate-change debate. "Katrina has become a symbolic event," says Russell Dynes, founding director of the University of Delaware's Disaster Recovery Center, in Newark.