In December 1967, Ehrlich wrote in the
New Scientist that the world would experience famines sometime between 1970 and 1985 due to population growth outstripping resources. He stated 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," or "be self-sufficient in food by 1971." He has been criticized as being wrong in these predictions. Ehrlich himself concedes that he did overstate his case here, underestimating the effects of the green revolution, but that part of the reason that there have not been such serious famines has been due to a reduction in birth rates that his book had argued were necessary. He also stated that in some areas The Population Bomb actually underestimated the dangers of high population - it made no mention of global warming, for instance.In 2006, Lara Knudsen wrote that Ehrlich's views were accepted by many population control advocates in the United States and Europe in the 1960s and 1970s. She chose a brief passage from the final chapter of Population Bomb to show that Ehrlich had discussed an extreme solution to extreme cases of overpopulation: "compulsory birth regulation... (through) the addition of temporary sterilants to water supplies or staple food. Doses of the antidote would be carefully rationed by the government to produce the desired family size."
In a 2004 interview, Ehrlich answered questions about the predictions he made in
The Population Bomb. He acknowledged that some of what he had written had not "come to pass", but went on to say that:
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. My view has become depressingly mainline!
Finally, Ehrlich noted that 600 million people were very hungry, billions were under-nourished, and stated that his predictions about disease and climate change were essentially correct.
In retrospect, Ehrlich feels that
The Population Bomb was "way too optimistic". He acknowledges that he underestimated the success of higher-yielding grains, and how that spurred further population growth. But he also points out that there have been perhaps 300 million deaths since the book was published that were caused in large part by malnourishment and undernourishment. He claims that the success of the "green revolution" of the 1970s is already running into the difficulties he and others predicted, while global hunger is now increasing.