What happens to the environment when humans disappear? Thirty years after the Chernobyl nuclear disaster, booming populations of wolf, elk and other wildlife in the vast contaminated zone in Belarus and Ukraine provide a clue.

On April 26, 1986, a botched test at the nuclear plant in Ukraine, then a Soviet republic, sent clouds of smoldering radioactive material across large swathes of Europe. Over 100,000 people had to abandon the area permanently, leaving native animals the sole occupants of a cross-border "exclusion zone" roughly the size of Luxembourg.