Marriage and family
On December 18, 1954, Paul Ehrlich married the former Anne Fitzhugh Howland, a research assistant. They remain married and have one child, Lisa Marie.

Academic activities
Ehrlich is president of the Center for Conservation Biology at Stanford University. He is a fellow of the American Association for the Advancement of Science, the American Academy of Arts and Sciences, and the American Philosophical Society.

Ehrlich's research group at Stanford currently works extensively on the study of natural populations of checkerspot butterflies (Euphydryas). Along with Dr. Gretchen Daly, he has conducted work in "countryside biogeography", or the study of making human-disturbed areas hospitable to biodiversity. Ehrlich continues to conduct policy research on population and resource issues, focusing especially on endangered species, cultural evolution, environmental ethics, and the preservation of genetic resources.

The Population Bomb
Ehrlich has written numerous books on the subjects of ecology, entomology, overpopulation, and related subjects. His best known book is The Population Bomb, published in 1968. A complete list of his writings can be found below in the "Writings" section.

The Population Bomb was written at the suggestion of David Brower, at the time the executive director of the Sierra Club, following an article Ehrlich wrote for the New Scientist magazine in December, 1967. In that article, Ehrlich predicted that the world would experience famines sometime between 1970 and 1985 due to population growth outstripping resources. Ehrlich wrote that "the battle to feed all of humanity is over... In the 1970s and 1980s hundreds of millions of people will starve to death in spite of any crash programs embarked upon now."

Ehrlich also stated, "India couldn't possibly feed two hundred million more people by 1980," and "I have yet to meet anyone familiar with the situation who thinks that India will be self-sufficient in food by 1971." These predictions wouldn't come to pass at those dates. In the book's 1971 edition, the latter prediction had been removed. An oft-cited cause of these famine aversions is the "Green Revolution", as it was called by the U.S. Agency for International Development in 1968. Another oft-cited cause was the sharp drop in the fertility rate which occurred in the developed world during the 1960s and 1970s.

Ehrlich has stated that despite his other work, the predictions of his first book are regularly cited as proof of extensive flaws in the environmental movement. At the same time, Ehrlich also notes that many things critics claim were "predictions" were actually scenarios. In the first edition of The Population Bomb, Ehrlich wrote: "The possibilities are infinite; the single course of events that will be realized is unguessable.

We can, however, look at a few possibilities as an aid to our thinking, using a device known as a 'scenario'. Scenarios are hypothetical sequences of events used as an aid in thinking about the future, especially in identifying possible decision points...Remember, these are just possibilities, not predictions." (p. 72)

Other activities
Ehrlich was one of the founders of the group Zero Population Growth in 1968, along with Richard Bowers and Charles Remington. Supporters point to the impact of The Population Bomb and the ZPG organization in helping to raise awareness about overpopulation and in helping to change U.S. laws to make birth control and other reproductive health care more easily available. The U.S. fertility rate dropped from 3.42 children per woman in the early 1960s to 1.8 by 1975, and ZPG credits Ehrlich's influence along with the efforts of National Organization for Women, Planned Parenthood of America, the American Civil Liberties Union, and the U.S. Supreme Court for helping to bring this about. However, since similar declines occurred throughout the developed world, the causality of these influences is far from clear.

He and his wife Anne were on the board of advisors of the Federation for American Immigration Reform until 2003. With Stephen Schneider and two other authors, writing in the January 2002 issue of Scientific American, he critiqued Bjørn Lomborg's The Skeptical Environmentalist.

Criticisms
Critics have compared Ehrlich to Thomas Malthus for his multiple predictions of famine and economic catastrophe. The leading critic of Ehrlich was Julian Lincoln Simon, a libertarian theorist and the author of the book The Ultimate Resource, a book which argues a larger population is a benefit, not a cost. To test their two contrasting views on resources, in 1980, Ehrlich and Simon entered into a wager over how the price of metals would move during the 1980s. Ehrlich predicted that the price would increase as metals became more scarce in the Earth's crust, while Simon insisted the price of metals had fallen throughout human history and would continue to do so. Ehrlich lost the bet. Indeed such was the decline in the price of the five metals Ehrlich selected, Simon would have won even without taking inflation into account.

In Ehrlich's books, many predictions are made, for example, The Population Bomb begins "[t]he battle to feed all of humanity is over. In the 1970s the world will undergo famines -- hundreds of millions of people are going to starve to death," while in "The End of Affluence", Ehrlich stated, "One general prediction can be made with confidence: the cost of feeding yourself and your family will continue to increase. There may be minor fluctuations in food prices, but the overall trend will be up". According to Ehrlich, the United States would see its life expectancy drop to 42 years by 1980 because of pesticide usage, and the nation's population would drop to 22.6 million by 1999.

Criticizing Ehrlich on similar grounds as Simon was Ronald Bailey, a leader in the wise use movement, who wrote a book in 1993 entitled Eco-Scam where he blasted the views of Ehrlich, Lester Brown, Carl Sagan and other environmental theorists. While of the repeated theorizing Simon complained "As soon as one predicted disaster doesn't occur, the doomsayers skip to another... why don't the [they] see that, in the aggregate, things are getting better? Why do they always think we're at a turning point -- or at the end of the road?"

In his book Betrayal of Science and Reason, Ehrlich discussed these earlier predictions of his and re-affirmed his stances on population and resource issues. Ehrlich also has critics on the political left. These include Betsy Hartmann, author of the 1987 book Reproductive Rights and Wrongs: The Global Politics of Population Control & Contraceptive Choice. Hartmann accuses Ehrlich and other environmentalists who focus on population control of misanthropy, and believes that such focus is antithetical to activism on issues of social class and feminism.

Ehrlich Answers Critics
In a question-fielding Grist Magazine interview (published on-line), Paul Ehrlich acknowledged some specific predictions he had made, in the years around the time his Population Bomb was published, that had not come to pass. However, as to a number of his fundamental ideas and assertions he maintained that facts and science proved them valid. (The Grist interview can be accessed via an external link provided near the bottom of this Wikipedia article.)

Among other things Ehrlich had to say was the following:

"When I wrote The Population Bomb in 1968, there were 3.5 billion people. Since then we've added another 2.8 billion — many more than the total population (2 billion) when I was born in 1932. If that's not a population explosion, what is? My basic claims (and those of the many scientific colleagues who reviewed my work) were that population growth was a major problem. Fifty-eight academies of science said that same thing in 1994, as did the world scientists' warning to humanity in the same year."