Biologist and environmentalist Paul Ehrlich has died

Paul Ehrlich, the Bing Professor of Population Studies, Emeritus, and professor of biology, emeritus, in the Stanford School of Humanities and Sciences, died Friday, March 13, 2026. He was 93. An evolutionary and population biologist and environmentalist, Ehrlich gained worldwide attention for his 1968 book, The Population Bomb, which predicted dire consequences due to the rapidly increasing human population and advocated population control.

Ehrlich was a prolific researcher, author, and activist throughout his career, and his work garnered many prestigious awards, including the Royal Swedish Academy of Sciences’ Crafoord Prize, an annual award established to recognize research in disciplines not eligible for Nobel prizes.     

“Without Paul, it would be difficult to fully appreciate the intricate evolutionary dance through which plants and animals co-evolve to sustain the functioning and the beauty of the natural world—and its impact on human well-being,” said Rodolfo Dirzo, the Bing Professor in Environmental Science and professor of biology in H&S and of Earth System science in the Stanford Doerr School of Sustainability. “It has been one of the great privileges of my life to benefit from his guidance, warmth, friendship, and unfailing bonhomie. Paul’s boundless passion for science and education at all levels leaves us a legacy of knowledge and a call to action for the preservation of all life-forms, ‘before they vanish.’”

A dedicated researcher and Jasper Ridge advocate

Ehrlich joined Stanford in 1959 as an assistant professor of biology. In an oral history conducted by the Stanford Historical Society, Ehrlich emphasized his love of research, which primarily focused on the dynamics and genetics of butterfly populations, the community ecology of birds, and the interactions of plants and the insects that eat them. A 1964 paper in Evolution, co-authored with Peter Raven, introduced the idea of co-evolution—in which interacting species, such as caterpillars and their host plants, help spur one another’s evolution—as an important subdiscipline of biology. In 1970, he told Current Biology that one of his favorite projects was controlling butterfly caterpillar populations with ants rather than pesticides. 

Ehrlich’s field work took him to every continent, but much of his work took place at the Rocky Mountain Biological Lab in Crested Butte, Colorado, and Stanford’s Jasper Ridge Biological Preserve (‘Ootchamin ‘Ooyakma)—which he implored the university to establish as protected space, a project he called “the most important thing I did at Stanford” in a 2023 interview. He loved the natural beauty of Stanford and was very proud of Jasper Ridge’s prominence as a renowned on-campus field site. Ehrlich also established the Center for Conservation Biology (now the Center for Nature & Society) and co-founded the Human Biology Program at Stanford.

“Even though his scholarship over the years sharply criticized where humans were heading, Paul always gave me—and I am sure many, many others—a sense of hope and encouragement to do work that contributes to society,” said Tadashi Fukami, professor of biology and of Earth system science and the preserve’s faculty director. “He played a central role in convincing the university to establish the preserve, the place he referred to as the most important research facility on the Stanford campus. Remembering his contribution makes me motivated ever more to do what I can to continue promoting the best research and education possible at Jasper Ridge.”

‘Fearlessly unconventional’ with a mischievous wit

In the course of authoring more than 700 scientific papers and articles and 30 books, Ehrlich often transcended disciplines, mixing his biological background with sociology, psychology, and economics, among other fields. He frequently worked with one or two co-authors, including his wife, Anne Howland Ehrlich, with whom he collaborated on policy research concerning human ecology, particularly the relationship between population, resources, and the state of the environment.

Ehrlich earned an astonishing number of awards and accolades, which he humbly attributed to merely being alive a long time. Among his awards are the Sierra Club John Muir Award, the WWF Duke of Edinburgh Conservation Award, the Blue Planet Award, the United Nations Environment Program’s Sasakawa Prize, the Heinz Award for the Environment, and the Tyler Prize for Environmental Achievement (these last three with Anne Ehrlich). In 1990, he was awarded a MacArthur Fellowship, and the same year he won the Crafoord Prize (with Edward O. Wilson) for “research of the dynamics and genetics of fragmented populations and the importance of the distribution pattern for their survival probabilities.”

Ehrlich was a fellow of the American Association for the Advancement of Science, the American Academy of Arts and Sciences, and the Royal Society. He was a member of the National Academy of Sciences and the American Philosophical Society.

Anyone who ever heard Ehrlich speak was struck by his larger-than-life personality. After an hour-long interview with Johnny Carson on the Tonight Show following the publication of The Population Bomb, he returned as a guest dozens of times to discuss topics including racism, nuclear war, and immigration. He was also a correspondent for NBC News. Ehrlich was simultaneously self-deprecating and confident. He had a mischievous sense of humor and a straightforward way of communicating that kept people listening, even when he was confronting them with humanity’s most daunting problems.

“Paul was fearlessly unconventional in his public persona and the topics he chose to write about,” said Marcus W. Feldman, the Burnet C. and Mildred Finley Wohlford Professor of Biology and director of the Morrison Institute for Population and Resource Studies in H&S. He first met Ehrlich in 1967 as a graduate student, and the two often collaborated on research and teaching over the following five decades. “Very few academics have had the courage he exemplified in challenging accepted doctrines. He, more than anybody, was responsible for Stanford becoming an international leader in population biology and environmental science.”

“He was a towering figure among his colleagues and one of a very small handful of scientists known to the general public,” said Chris Field, the Perry L. McCarty director of the Stanford Woods Institute for the Environment, where Ehrlich was a fellow for many years. “It was always thrilling to be in the same room as Paul. He had a witty insight about everything, usually offered with a hilarious story or a sly jab at a favorite opponent. His booming baritone voice often shook the room, but he was the world’s best listener when a young colleague had a challenge or faced a loss. Paul cared deeply about the fate of the world but even more deeply about the people close to him.

“For me, Paul’s biggest influence was demonstrating that one can be both a great scientist and a great advocate for social progress,” continued Field, a professor of Earth system science and of biology. “Paul brought a penetrating intellect and a strong moral compass to everything he did, giving future generations both inspiration and example. It is thanks to Paul’s pioneering vision that we have a field of sustainability science, a school of sustainability at Stanford, and thousands of scholars around the world dedicating themselves to practical solutions for people and the planet.”

Inspired by a childhood chasing butterflies     

Paul Ralph Ehrlich was born May 29, 1932, in Philadelphia, Pennsylvania, to Ruth (Rosenberg) Ehrlich, a public school Latin teacher, and William Ehrlich, a salesman. He grew up in Maplewood, New Jersey, and got a head start on his eventual studies by chasing butterflies and dissecting frogs. Seeing a reduction in butterflies—which he later attributed to the pesticide DDT and construction—inspired an interest in environmentalism. His path to becoming a career scientist was further solidified by working at the Museum of Natural History in New York as a high school student. He mounted butterflies under the supervision of the curator of insects, Charles Michener, who would later be Ehrlich’s professor at the University of Kansas. 

In 1953, Ehrlich graduated from the University of Pennsylvania with a bachelor of arts in zoology and spent his undergraduate summers working for the Canadian Northern Insect Survey. He earned his master’s and doctorate in entomology from the University of Kansas in 1955 and 1957.

In his free time, Ehrlich was a licensed pilot and enjoyed reading, especially about anthropology and military history. He was also fond of going to the movies.

He is survived by his wife of 72 years, Anne; his daughter, Lisa Daniel; his sister, Sally Kellock; two granddaughters; one step-granddaughter; two great-grandchildren; and four step-great-grandchildren. A celebration of life is being planned for later this spring.