Paul R. Ehrlich, an eminent ecologist and population scientist whose best-selling book, “The Population Bomb,” was celebrated as a prescient warning of a coming age of food shortages and famine but later criticized by conservatives and academic rivals for what they called its sky-is-falling rhetoric, died on Friday in Palo Alto, Calif. He was 93. His death, at a nursing facility in the retirement community where he lived, was caused by complications of cancer, his daughter, Lisa Marie Daniel, said. As a young professor of biology at Stanford University in the mid-1960s, Dr. Ehrlich was known for his absorbing lectures...