This one is on one the heroes of the last century, Rachel Carson.

Since 1782, the bald eagle has been the national symbol for the US. Yet, more than 50 years ago, the species was in danger of extinction: in 1966, only 487 pairs remained. The primary culprit was sneaky – a chemical pesticide called DDT. Sprayed from planes to control mosquitoes, DDT seeped into water bodies, where it worked its way up the food web, through aquatic plants to fish, and then to bald eagles who ate the fish. DDT caused the birds to produce thin eggshells so that the eggs often broke during incubation or didn’t hatch. Thanks to writer and scientist Rachel Carson, bald eagle populations have rebounded. (More here)