Paul Ralph Ehrlich (May 29, 1932 – March 13, 2026) was an American scientist, writer, and environmental advocate who warned about the effects of population growth, such as food shortages and the use up of natural resources. He was the Bing Professor in the Department of Biology at Stanford University. He began working at Jasper Ridge Biological Preserve in 1959. Along with other biology professors, he helped Stanford University protect Jasper Ridge in 1973 as a biological preserve and a long-term research area for students and faculty.

Ehrlich became well known for the 1968 book The Population Bomb, which he co-authored with his wife, Anne H. Ehrlich. In the book, they wrote that "in the 1970s, hundreds of millions of people will starve to death despite any efforts to prevent it now." Some historians and critics describe Ehrlich as a neo-Malthusian.

Opinions about Ehrlich’s warnings are divided. Statistician Paul A. Murtaugh said Ehrlich was mostly correct about population growth dangers. However, others criticized him for being too negative and for some of his predictions not coming true. In 2004, Ehrlich admitted that population growth was decreasing but believed that overuse of resources by wealthy countries remained a serious problem. He said his warnings about disease and climate change were still accurate. Journalist Dan Gardner pointed out that Ehrlich sometimes took credit for correct predictions but did not always admit when he was wrong.

Early life, education and academic career

Ehrlich was born in Philadelphia, Pennsylvania, to William Ehrlich and Ruth Rosenberg. His father worked as a shirt salesman, and his mother was a teacher and scholar who studied Greek and Latin. Ehrlich’s mother’s family came to the United States from Germany in the 1840s, and his father’s grandparents later moved from the Galician and Transylvanian regions of the Austrian Empire. Ehrlich grew up in a Jewish household that opposed Zionism. As a child, his family moved to Maplewood, New Jersey, where he attended Columbia High School and graduated in 1949.

Ehrlich studied insects, focusing on butterflies and moths. He earned a bachelor’s degree in zoology from the University of Pennsylvania in 1953, a master’s degree from the University of Kansas in 1955, and a Ph.D. from the University of Kansas in 1957. His doctoral work was supervised by Charles Duncan Michener, a well-known researcher who studied bees. Ehrlich’s dissertation was titled The Morphology, Phylogeny and Higher Classification of the Butterflies (Lepidoptera: Papilionoidea).

During his studies, Ehrlich helped survey insects in the Bering Sea and Canadian Arctic. Later, with a fellowship from the National Institutes of Health, he studied the genetics and behavior of parasitic mites. In 1959, he became a teacher at Stanford University. He gained recognition for introducing the term coevolution in a 1964 paper he co-wrote with botanist Peter H. Raven. In this paper, they argued that insects and their food plants influenced each other’s development, leading to the wide variety of both groups.

This paper had a major impact on the field of chemical ecology. In 1966, Ehrlich was promoted to professor of biology, and in 1977, he was named Bing Professor. In 1984, he started the Center for Conservation Biology at Stanford University. He was a member of several prestigious organizations, including 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

In April 1967, a lecture by Paul Ehrlich about overpopulation was broadcast on radio through the Commonwealth Club of California. The lecture was well-received, leading to interest in writing a book on the topic. David Brower, the director of the Sierra Club, and Ian Ballantine of Ballantine Books encouraged Ehrlich to write a book. Ehrlich and his wife, Anne H. Ehrlich, worked together on the book The Population Bomb. However, the publisher required only one author’s name to be listed, so only Paul Ehrlich was credited.

Although Ehrlich was not the first person to warn about population issues—concerns were common in the 1950s and 1960s—his ability to engage the public through media helped raise awareness. Ehrlich appeared on The Tonight Show Starring Johnny Carson more than twenty times, with one interview lasting an hour.

The original edition of The Population Bomb began with the statement: Ehrlich argued that the human population was too large, and while the effects of overpopulation could be lessened, severe famines, disease, social unrest, and other negative outcomes could not be avoided.

Ehrlich suggested solutions to overpopulation, including government programs that combine agricultural development with population control. He supported voluntary measures such as easy access to birth control and abortion.

Over time, Ehrlich’s predictions faced scrutiny and criticism. The New York Times noted that his "apocalyptic predictions fell as flat as ancient theories about the shape of the Earth." Science writer 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 forced sterilizations. Ehrlich’s focus on Delhi’s population over Paris’s, despite Paris having a much larger population at the time, was criticized for relying on emotions rather than data.

Neither Ehrlich nor his wife publicly renounced their predictions, stating they were largely correct despite noted errors. In The Population Explosion, the Ehrlichs claimed the population crisis they described in The Population Bomb had occurred, with hunger and famine becoming more urgent.

Many accepted the idea of a population problem. Sociologist Frank Bean wrote in The New York Times that addressing population issues was "imperative." Others, like Thomas J. Espenshade, criticized the Ehrlichs for being overly alarmist. The book was also criticized for suggesting that government control, not voluntary family planning, was necessary to manage population growth. Critics accused the Ehrlichs of supporting government control over reproductive choices and unclear limits on how much authority governments should have.

Later analysis showed that some of the book’s claims were incorrect. For example, the idea that global food production had already peaked was false, and predictions of severe food shortages in India during the 1990s did not happen.

In The Population Explosion, the Ehrlichs discussed their view of an "optimal" human population size, estimating it to be between 1.5 and 2 billion people based on current technology and conditions. They suggested policies to influence fertility rates.

During a 2004 interview, Ehrlich acknowledged that some predictions from The Population Bomb did not occur but stated he felt "little embarrassment" and reaffirmed his belief that overpopulation is a major problem. He noted that 58 science academies and a global scientists’ warning in 1994 supported his views. Ehrlich claimed that 600 million people were very hungry and that his predictions about disease and climate change were correct. He later said The Population Bomb was "way too optimistic" in predicting widespread famine by 1985.

In 2008, Ehrlich criticized the United States for needing to control its population and consumption to set an example for other countries. He still supported government efforts to discourage large families, such as higher taxes for larger households.

In 2011, as the world’s population reached seven billion, Ehrlich argued that the next two billion people would cause more environmental harm than the previous two billion, as resources would become scarcer. As of 2013, Ehrlich continued research on population and resource issues, focusing on endangered species, environmental ethics, and biodiversity. With Dr. Gretchen Daily, he studied how to make human-altered areas support wildlife. His team at Stanford University studied the Bay checkerspot butterfly.

Ehrlich’s predictions about population-related disasters, such as widespread starvation in the 1970s and 1980s, did not occur. Slower population growth and advances in food production increased food supplies faster than population growth. Ehrlich still believed the human population is too large, threatening survival and the environment. In 2015, he said he would use "even more apocalyptic" language if he wrote the book today. In 2018, he stated the optimal population size is between 1.5 and 2 billion. In 2022, he contributed to a report estimating a sustainable population between 2 and 4 billion people.

Reception

During the 1960s and 1970s, when Paul Ehrlich made his most serious warnings, many experts believed that population growth could harm the future of human civilization. However, experts disagreed about how serious the problem was and what steps should be taken to address it.

Since that time, critics have challenged Ehrlich’s main ideas about overpopulation and its effects on the environment and society. They also questioned his solutions and the specific predictions he made starting in the late 1960s.

One common criticism is that Ehrlich’s predictions did not come true. For example, Ronald Bailey of Reason magazine called Ehrlich an "irrepressible doomster" who "has never been right in any of his forecasts of imminent catastrophe." On the first Earth Day in 1970, Ehrlich warned that "in ten years all important animal life in the sea will be extinct. Large areas of coastline will have to be evacuated because of the stench of dead fish."

In a 1971 speech, Ehrlich predicted that by the year 2000, the United Kingdom would be "a small group of impoverished islands, inhabited by some 70 million hungry people." He also said, "If I were a gambler, I would take even money that England will not exist in the year 2000." When this did not happen, Ehrlich responded that "When you predict the future, you get things wrong. How wrong is another question. I would have lost if I had taken the bet. However, if you look closely at England, what can I tell you? They're having all kinds of problems, just like everybody else."

In The Population Bomb, Ehrlich wrote that "India couldn't possibly feed two hundred million more people by 1980." In 1967, he called for cutting off emergency food aid to India as "hopeless." This position was later criticized, as India’s food production increased significantly through the Green Revolution, and its people’s caloric intake rose even as its population doubled.

Canadian journalist Dan Gardner, in his 2010 book Future Babble, argues that Ehrlich has not been honest about his mistakes. For example, Ehrlich rarely admits errors in predicting material shortages, mass starvation, or the negative effects on specific countries. However, he claims credit for "predicting" the rise of AIDS or global warming. Gardner says Ehrlich’s actions show a double standard, as he takes credit for some predictions but ignores others.

In the case of disease, Ehrlich predicted increases in illness due to overcrowding or weak immune systems from starvation. However, it is "a stretch" to claim this was a prediction about AIDS in the 1980s. Similarly, Ehrlich described global warming as a possible scenario, but he does not take responsibility for failed predictions. Gardner believes Ehrlich shows signs of cognitive dissonance, and his refusal to admit errors makes his current views questionable.

Barry Commoner criticized Ehrlich’s 1970 statement that "When you reach a point where you realize further efforts will be futile, you may as well look after yourself and your friends and enjoy what little time you have left. That point for me is 1972." Gardner also criticized Ehrlich for supporting strategies proposed by William and Paul Paddock in their book Famine 1975!, which suggested ending food aid to countries like India and Egypt. Ehrlich wrote in The Population Bomb that "there is no rational choice except to adopt some form of the Paddocks' strategy as far as food distribution is concerned." If this strategy had been used, countries like India and Egypt, which relied on food aid, would likely have suffered famines. Instead, both countries increased food production and now feed larger populations without relying on aid.

Another group of critics, often from the political left, argues that Ehrlich focuses too much on overpopulation as a problem rather than on the unequal distribution of resources. Barry Commoner said Ehrlich’s solutions were politically unacceptable because they implied coercion and would harm poor people. He believed that technological and social progress would naturally reduce population growth and environmental damage. Ehrlich denies being racist and says his policies would not be repressive if properly implemented.

In a 2018 interview with The Guardian, Ehrlich praised The Population Bomb for starting a global debate on population issues. However, he acknowledged the book’s weaknesses, such as not emphasizing overconsumption and inequality enough. He also countered accusations of racism, saying "too many rich people in the world is a major threat to the human future, and cultural and genetic diversity are great human resources." He advocated for an "unprecedented redistribution of wealth" to reduce overconsumption by the wealthy, but he said the wealthy, who control global systems, are unlikely to allow such changes.

In a 2022 paper, Ehrlich and his colleague Rodolfo Dirzo argued that reducing fertility rates among "the overconsuming wealthy and middle classes" and reducing wasteful consumption could help reduce the scale of human activity to address the extinction crisis.

Economist Julian Simon argued in 1980 that overpopulation is not a problem because humans will adapt to changing conditions. He believed that creativity would improve living standards and that most resources could be replaced. Simon noted that prices for most commodities had decreased over time. Ehrlich called Simon’s view a "space-age cargo cult" of economists who believed human ingenuity could replace scarce resources. He reasserted that population growth was outpacing the Earth’s ability to provide food, fresh water, and minerals.

This debate led to the Simon–Ehrlich wager, a bet about resource prices over ten years. Ehrlich chose ten commodities, mostly metals, predicting their prices would rise. However, their average price decreased by about 30% over ten years, and Ehrlich lost the bet. Simon and Ehrlich could not agree on the terms of a second bet.

Ehrlich argued that humanity has delayed disaster through intensive agricultural techniques, such as those introduced during the Green Revolution. He claimed that growing populations and affluence are stressing the environment due to factors like biodiversity loss, overfishing, global warming, urbanization, chemical pollution, and competition for raw materials. He said reducing consumption and population growth is critical to protecting the environment and maintaining living standards, but current growth rates are still too high for a sustainable future.

Other activities

Paul Ehrlich was one of the people who started the group called Zero Population Growth, which later changed its name to Population Connection, in 1968. He worked with Richard Bowers and Charles Lee Remington. In 1971, Ehrlich was chosen to join the Common Cause National Governing Board. He and his wife, Anne, were members of the advisory board for the Federation for American Immigration Reform until 2003. He also supported an organization called Population Matters, which was previously known as the Optimum Population Trust.

In 1977, Ehrlich wrote about pollution after reviewing a doctoral dissertation by his student, Edward Goth III. He stated, "Fluorides can build up in food chains, and more evidence is showing that fluorides could harm the environment."

Ehrlich gave speeches at conferences in Israel about desertification. He said, "True Zionists should have small families."

Personal life

Ehrlich married Anne H. Ehrlich (née Howland) in December 1954. They had one daughter named Lisa Marie. He announced that he had a vasectomy in 1963 after his daughter was born. Ehrlich died from complications caused by cancer on March 13, 2026, at a retirement community in Palo Alto, California. He was 93 years old.

Awards and honors

• Received the John Muir Award from the Sierra Club in 1980
• Received the Gold Medal Award from the World Wildlife Fund International in 1987
• Received a MacArthur Prize Fellowship in 1990
• Received the Crafoord Prize in biosciences from the Royal Swedish Academy of Sciences in 1990
• Won the ECI Prize in terrestrial ecology in 1993
• Received a World Ecology Award from the International Center for Tropical Ecology at the University of Missouri in 1993
• Received the Volvo Environment Prize in 1993
• Received the United Nations Sasakawa Environment Prize in 1994
• Received the 1st Annual Heinz Award in the Environment (with Anne Ehrlich) in 1995
• Received the Tyler Prize for Environmental Achievement in 1998
• Received the Dr. A. H. Heineken Prize for Environmental Sciences in 1998
• Received the Blue Planet Prize in 1999
• Received the Eminent Ecologist Award from the Ecological Society of America in 2001
• Received the Distinguished Scientist Award from the American Institute of Biological Sciences in 2001
• Received the Ramon Margalef Prize in Ecology from the Generalitat of Catalonia in 2009
• Became a Fellow of the Royal Society in London in 2012
• Received the BBVA Foundation Frontiers of Knowledge Award in Ecology and Conservation Biology in 2013

Works

• Ehrlich, P. R. (2010). "The MAHB, the Culture Gap, and Some Really Inconvenient Truths." PLOS Biology. 8 (4) e1000330. doi: 10.1371/journal.pbio.1000330. PMC 2850377. PMID 20386722.
• Ceballos, Gerardo; Ehrlich, Paul R.; Barnosky, Anthony D.; García, Andrés; Pringle, Robert M.; Palmer, Todd M. (2015). "Accelerated modern human–induced species losses: Entering the sixth mass extinction." Science Advances. 1 (5) e1400253. Bibcode: 2015SciA….1E0253C. doi: 10.1126/sciadv.1400253. PMC 4640606. PMID 26601195.
• Ceballos, Gerardo; Ehrlich, Paul R.; Dirzo, Rodolfo (May 23, 2017). "Biological annihilation via the ongoing sixth mass extinction signaled by vertebrate population losses and declines." PNAS. 114 (30): E6089–E6096. Bibcode: 2017PNAS..114E6089C. doi: 10.1073/pnas.1704949114. PMC 5544311. PMID 28696295.
• Dirzo, Rodolfo; Ceballos, Gerardo; Ehrlich, Paul R. (2022). "Circling the drain: the extinction crisis and the future of humanity." Philosophical Transactions of the Royal Society B. 377 (1857) 20210378. doi: 10.1098/rstb.2021.0378. PMC 9237743. PMID 35757873.