Great Whales Rebound as Marine Engineers

In the heyday of commercial whaling in the 19th and 20th centuries, whales were killed by the tens of thousands. By the time an international moratorium was put in place in 1986, some populations of the giant marine mammals had declined by an estimated 66 to 90 percent. Since then, whale populations have rebounded and, as VOA’s Rosanne Skirble reports, they are improving the ocean environment.