Paul Ralph Ehrlich (May 29, 1932 – March 13, 2026) was an American biologist, author, and environmentalist known for his predictions and warnings about the consequences of population growth, including famine and resource depletion. Ehrlich was the Bing Professor of Population Studies of the Department of Biology of Stanford University. He started working at Jasper Ridge Biological Preserve in 1959. He along with many other biology professors, led the efforts for Stanford University to designate and protect Jasper Ridge in 1973 as a biological preserve and as a long-term research facility for faculty and students.
Ehrlich became well known for the controversial 1968 book The Population Bomb, which he co-authored with his wife Anne H. Ehrlich, in which they famously stated that "[i]n the 1970s hundreds of millions of people will starve to death in spite of any crash programs embarked upon now." This position has led historians and critics to describe Ehrlich as a neo-Malthusian.
There are mixed views on Ehrlich's assertions on the dangers of expanding human populations. While statistician Paul A. Murtaugh says that Ehrlich was largely correct, Ehrlich has been criticized for his approach and views, both for their pessimistic outlook and for the failure of his predictions. In 2004, Ehrlich had acknowledged that population growth was in decline, but had believed that overconsumption by wealthy nations was a major problem. He maintained that his warnings about disease and climate change were essentially correct. Journalist Dan Gardner criticized Ehrlich for his cognitive dissonance in forecasting, asserting that Ehrlich took credit for his successful predictions but failed to acknowledge his mistakes.
Early life, education and academic career
Ehrlich was born in Philadelphia, Pennsylvania, the son of William Ehrlich and Ruth Rosenberg. His father was a shirt salesman and his mother was a Greek and Latin scholar and public school teacher. Ehrlich's mother's German ancestors arrived in the United States in the 1840s, and his paternal grandparents emigrated there later from the Galician and Transylvanian part of the Austrian Empire. Ehrlich has been described as having grown up in a household that was Jewish but anti-Zionist. During his childhood his family moved to Maplewood, New Jersey, where he attended Columbia High School, graduating in 1949.Polner, Murray. American Jewish Biographies, p. 88. Facts on File, 1982. . Accessed August 3, 2019. "his childhood his family moved to Maplewood, New Jersey, where he was graduated from Columbia High School in 1949."
By training, Ehrlich was an entomologist specializing in Lepidoptera (butterflies). He earned a bachelor's degree in zoology from the University of Pennsylvania in 1953, an M.A. from the University of Kansas in 1955, and a Ph.D. from the University of Kansas in 1957, supervised by the prominent bee researcher Charles Duncan Michener (the title of his dissertation: The Morphology, Phylogeny and Higher Classification of the Butterflies (Lepidoptera: Papilionoidea)).Ehrlich, Paul R., "The Morphology, Phylogeny and Higher Classification of the Butterflies (Lepidoptera: Papilionoidea)," Ph.D. dissertation, University of Kansas, May 1957.
During his studies he participated in surveys of insects in the areas of the Bering Sea and Canadian arctic, and then, with a National Institutes of Health fellowship, investigated the genetics and behavior of parasitic mites. In 1959 he joined the faculty at Stanford University. He became well known for popularizing the term coevolution in an influential 1964 paper co-authored with the botanist Peter H. Raven, where they proposed that reciprocal selective responses between insects and their food plants explains the extreme diversification of plants and insects.
This paper was highly influential on the then-nascent field of chemical ecology. He was promoted to professor of biology in 1966, and appointed to the Bing Professorship in 1977.Lewis, J. "Biologist Paul R. Ehrlich. Six billion and counting". Scientific American October 2000, pages 30, 32. In 1984, he founded the Center for Conservation Biology at Stanford University. He was a fellow of the American Association for the Advancement of Science, the United States National Academy of Sciences, the American Academy of Arts and Sciences and the American Philosophical Society.
Overpopulation debate
A lecture that Ehrlich gave on the topic of overpopulation at the Commonwealth Club of California was broadcast by radio in April 1967. The success of the lecture caused further publicity, and the suggestion from David Brower the executive director of the environmentalist Sierra Club, and Ian Ballantine of Ballantine Books to write a book concerning the topic. Ehrlich and his wife, Anne H. Ehrlich, collaborated on the book, The Population Bomb, but the publisher insisted that a single author be credited; only Paul's name appears as an author.
Although Ehrlich was not the first to warn about population issues — concern had been widespread during the 1950s and 1960s — his charismatic and media-savvy methods helped publicize the topic. The Tonight Show Starring Johnny Carson had Ehrlich on as a guest more than twenty times, with one interview lasting an hour.
Writings The Population Bomb (1968)
The original edition of The Population Bomb began with the statement: Ehrlich argued that the human population was too great, and that while the extent of disaster could be mitigated, humanity could not prevent severe famines, the spread of disease, social unrest, and other negative consequences of overpopulation.
Ehrlich has proposed different solutions to the problem of overpopulation. In The Population Bomb he wrote, "We must have population control at home, hopefully through a system of incentives and penalties, but by compulsion if voluntary methods fail. We must use our political power to push other countries into programs which combine agricultural development and population control." Voluntary measures he has endorsed include the easiest possible availability of birth control and abortion.
Decades later, Ehrlich's continued prominence and the failure of the book's predictions to materialize led to renewed scrutiny and criticism. The New York Times said his "apocalyptic predictions fell as flat as ancient theories about the shape of the Earth".
Science author Charles C. Mann wrote that the book's predictions "fueled an anti-population-growth crusade that led to human rights abuses around the world", including coercive population control policies and even forced sterilizations. Ehrlich's pointed criticism of India in particular (for instance, emphasizing the overpopulation of Delhi rather than Paris, which had nearly triple Delhi's population at the time of writing) has been criticized for focusing much more on "feelings" than on actual data.
Neither of the Ehrlichs have ever publicly renounced predictions, instead insisting that they were largely correct, despite the errors noted by many experts.
The Population Explosion (1990) The Population Explosion argues that the population catastrophe outlined in the Ehrlichs' earlier work The Population Bomb had in fact come to pass, and that "hunger is rife and famine and plague ever more imminent".
Many accepted the premise of a looming population problem; for instance the sociologist Frank Bean wrote in a review of the book for the New York Times that "it is not merely prudent but imperative that we confront population issues, and do so now". Others, like the sociologist Thomas J. Espenshade, criticized the Ehrlichs for an "alarmist" tone. The book was also criticised for its approach to family planning, which argued voluntary family planning was insufficient to deal with population growth and government-directed population control was necessary. The Ehrlichs were accused of advocating the curtailment of reproductive freedoms and giving the state a larger role in such decisions, while leaving ambiguous "just how authoritarian a solution they are willing to endorse."
Subsequent attention to the book scrutinized its descriptions of an unfolding overpopulation catastrophe. The book's contention that global food production had already peaked proved to be incorrect. Similarly, the prediction that India faced catastrophic food shortage in the 1990s failed to materialize.
Optimum Human Population Size (1994) In this paper, the Ehrlichs discussed their opinion on the 'optimal size' for human population, given their assessment of the current technological situation. Their "back-of-the-envelope" estimate was that the optimal human population, given "prevailing biophysical and social conditions" and satisfying certain criteria, is "in the vicinity of 1.5 to 2 billion people". They referred to establishing "social policies to influence fertility rates."
After 2000 During a 2004 interview, Ehrlich answered questions about the predictions he made in The Population Bomb. He acknowledged that some of what he had published had not occurred, but stated that he felt "little embarrassment" and reaffirmed his basic opinion that overpopulation is a major problem. He noted that, "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!" Ehrlich asserted that 600 million people were very hungry while billions were under-nourished, and insisted that his predictions about disease and climate change were essentially correct. Retrospectively, Ehrlich said that The Population Bomb, which predicted a widespread famine by 1985 that never materialized, was actually "way too optimistic".
In a 2008 discussion hosted by the website Salon, Paul Ehrlich was more critical of the United States specifically, claiming that it should control its population and consumption as an example to the rest of the world. He still professed a belief that governments should discourage people from having more than two children, suggesting, for example, a higher tax rate for larger families.
In 2011, as the world's population passed the seven billion mark, Ehrlich argued that the next two billion people on Earth would cause more damage than the previous two billion, as humans now increasingly would have to resort to using more marginal and environmentally damaging resources. As of 2013, Ehrlich continued to perform policy research concerning population and resource issues, with an emphasis upon endangered species, cultural evolution, environmental ethics, and the preservation of genetic resources. Along with Dr. Gretchen Daily, he performed work in countryside biogeography; that is, the study of making human-disturbed areas hospitable to biodiversity. His research group at Stanford University examined extensive natural populations of the Bay checkerspot butterfly ().
The population-related disaster that Ehrlich predicted has failed to materialize, including the "hundreds of millions" of starvation deaths in the 1970s and the tens of millions of deaths in the United States in the 1970s and 1980s. Slowing of population growth rates and new food production technologies have increased the food supply faster than the population. Ehrlich continued to stand by his general thesis that the human population is too large, posing a direct threat to human survival and the environment of the planet. In 2015, he stated that if he were to write the book then, "My language would be even more apocalyptic today." In 2018, he emphasized his view that the optimum population size is between 1.5 and 2 billion people. In 2022, he was a contributor to the "Scientists' warning on population", published by Science of the Total Environment, which estimated that a sustainable population would be between 2 and 4 billion people.
Reception Responses to predictions