Perhaps one of the best examples of how mankind can screw up a good thing—and then work to correct it—can be found in the story of the striped bass that once roamed the Savannah River in huge numbers.
The Georgia river is exponentially cleaner than it once was and virtually all major pollution sources are permitted, monitored and regulated. Ironically, the same factories and sewage plants that once were the major polluters have done the most to make those improvements.