Thomas E. Lovejoy III, an ecologist who dedicated his career to preserving the Amazon rainforest and educating Washington policymakers and the public about the dangers of climate change, died Dec. 25 at his home in McLean, Va. He was 80.

His daughter Elizabeth Lovejoy said he died of pancreatic cancer.

Dr. Lovejoy was considered one of the most consequential conservation biologists of his generation for his ability to meld field research — on how fragmented forests deplete diversity and how they can store carbon if protected — with environmental and policy work to draw attention to the plight of the Amazon, the world’s largest and most diverse rainforest.

Among his many innovations, he introduced the term “biological diversity” in 1980; he made the first projection of global extinction rates in a report to President Jimmy Carter; and he devised the concept of “debt-for-nature swaps,” in which part of a country’s foreign debt is forgiven in exchange for investments in conservation.

Throughout the course of Dr. Lovejoy’s career, much of it based in the Washington area for organizations such as the Smithsonian Institution, the World Wildlife Fund and George Mason University, he became increasingly alarmed about climate change and the global extinction crisis. In spreading this message, he allied with lawmakers and Hollywood celebrities, often leading them on tours of his research station north of Manaus, the capital of the Brazilian state of Amazonas, known as Camp 41.

“I count myself lucky to have had the great privilege of staying there several times, learned the proper way to sleep in a hammock, identify the source of the loudest snoring, and I always came away inspired and connected to the Brazilian Amazon in the deepest way,” Carter Roberts, president and CEO of the World Wildlife Fund in the United States, said in a statement, describing Lovejoy as “truly a legend” whose “impact will be felt for decades to come.”

With his pince-nez glasses and vast bow tie collection, Dr. Lovejoy was also a fixture in Washington, testifying on Capitol Hill, meeting with journalists and hosting senators and scientists for dinners at Drover’s Rest, his historic log cabin in McLean, filled with books and curiosities from the natural world. Despite the severity of the forest destruction in the Amazon and elsewhere, and the grave projections of the warming world, he maintained a sense of optimism that humans could find ways to change course and avert the worst outcomes.

Even in late 2019, when he and longtime colleague Carlos Nobre of the University of São Paulo wrote that clear-cutting, rising temperatures and wildfires were pushing the Amazon to a tipping point, where it was “teetering on the edge of functional destruction and, with it, so are we,” he held out a sliver of hope.

“In this case, it’s not going to be instantaneous, and that’s good news,” he told The Washington Post at the time. “It allows you to do something about it.”

Thomas Eugene Lovejoy was born in New York City on Aug. 22, 1941. He was an only child and grew up in a privileged setting on the Upper East Side. Both his father and grandfather had been chief executives of the Manhattan Life Insurance Co.

Dr. Lovejoy told The Post he chose his boarding school, the Millbrook School in Dutchess County, N.Y., because it had a zoo. He said the school’s first biology teacher and zoo founder, Frank Trevor, inspired him to study biology, particularly birds, and “awakened me to the fascination of nature and biology.”

He received a bachelor’s degree in biology in 1964 from Yale University and stayed at Yale to complete his PhD, also in biology, in 1971.

Thomas Lovejoy, a conservation biologist credited with coining the term “biological diversity,” holds a Thorny Devil in Australia in September 2016. (Family photo)

In the summer of 1965, while in graduate school, Dr. Lovejoy got a chance to visit the Brazilian Amazon while working with the Evandro Chagas Institute in the forest outside Belém, a trip that persuaded him to do his doctoral dissertation there on the ecology of birds.

“I’ve always been fascinated with biological diversity, and imagined having a life full of scientific adventures — and the Amazon was this incredible, tropical wilderness,” he told a Brazilian magazine in 2015, after a half-century visiting the country. “So it was like I had died and gone to heaven. It was sheer fascination, and I gradually began to move from just doing science to doing science and environmental conservation. The Amazon is one of the most important places to work in the world.”

The Biological Dynamics of Forest Fragments Project, which Dr. Lovejoy launched in 1979 with the support of Brazil’s National Institute of Amazonian Research and the Smithsonian, is one of the world’s biggest — and longest-running — biological ecosystem experiments. Consisting of differently sized plots of Amazon rainforest near Manaus, the research project has cast light on the importance of “edge effects” on forests that are disturbed by humans, either from the creation of roads and infrastructure or from outright deforestation. The research found that when forest edges are created, the remaining areas of rainforest most closely exposed to them become hotter and drier and lose carbon, and the diversity of species within them declines.

Near the test forest plots, in a cool expanse of intact rainforest, lies Camp 41, which for some nonscientists may be even more famous than the research project with which it was associated. A humble site with screened hammocks for beds and natural river baths, it was a place where Dr. Lovejoy brought many policymakers and other influential people to visit the rainforest in its undisturbed state. For some, the experience included encountering the majestic harpy eagle, one of the world’s most powerful avian predators and threatened species that has been known to nest near the camp.

The solution to climate change that has nothing to do with cars or coal

As a consequence, conservationists and governments sought to create protected areas and understand the effect of development. Nobre, one of his collaborators on other research in Brazil, said that many of the cattle farms where Dr. Lovejoy focused his research are now abandoned, allowing scientists to study how forests regenerate and which species return.

Dozens of politicians and celebrities, including Al Gore and Olivia Newton-John, made the trip into the jungle to visit Camp 41. Tom Cruise nicknamed Dr. Lovejoy “Indy,” after Indiana Jones, following a trip to the camp. Family members recalled his love of practical jokes, including planting fake tarantulas in hammocks.

Former senator Timothy E. Wirth (D-Colo.), president emeritus of the United Nations Foundation, was a close friend who traveled with Dr. Lovejoy to the Arctic and the South Pole, rafted through the Grand Canyon and explored deep into the Amazon.

“He was incredibly warm and mischievous, as well as being a first-rate scientist,” Wirth said in an interview. “Nobody more fun to be with.”

On one congressional delegation visit to the Amazon, after the 1988 assassination of Brazilian rubber tapper and environmentalist Chico Mendes, Wirth recalled that the Brazilian government suspected the U.S. senators were investigating Mendes’s death and sent police to keep watch.

“Serge-suited goons followed us all over the Amazon, sweating like crazy,” Wirth said.

Before meeting Dr. Lovejoy, Ben Bradlee, former executive editor of The Washington Post, had been somewhat skeptical of environmental concerns, according to his wife, Sally Quinn.

“He used to say, ‘Don’t tell me that every time I squirt an underarm deodorant it’s going to penetrate the ozone layer,’ ” Quinn recalled.

But after his visit to the Amazon in 1988 with Dr. Lovejoy — and laughing about the infamous candiru, an Amazonian fish supposedly capable of swimming up a man’s urethra — Bradlee returned a convert.

“He said, ‘Well, I guess I’ve become a f—ing tree hugger,’ ” Quinn said. Bradlee assigned “somebody to cover the environment and he got with the program.”

As for Dr. Lovejoy, Quinn described him as a Renaissance man, knowledgeable about politics, literature, food and wine, in addition to science.

“Everybody loved him, he was so aptly named,” she said. “He was really lovely, he was a wonderful person, and joyous.”

Dr. Lovejoy also worked for the World Bank, the United Nations Foundation, and the H. John Heinz III Center for Science, Economics and the Environment and was affiliated with numerous environmental and academic institutions. He had held the title of university professor at George Mason since 2010. He was a major contributor to the Amazon Assessment Report, presented at the United Nations climate conference in Glasgow, Scotland, in November.

His marriage to Charlotte Seymour ended in divorce. Survivors include three daughters, Katherine L. Petty of Telluride, Colo., Elizabeth P. Lovejoy of Washington and Anne L. Jenkins of Arlington, Va.; and six grandchildren.

Chris Mooney and Juliet Eilperin contributed to this report.


A previous version of this article incorrectly identified Frank Trevor as the founder of the Millbrook School. He was the founder of the school’s zoo and its first biology teacher. This article has been corrected.