AUSTIN – When classes resume at the University of Texas at Austin this week, 90 impressionable undergrads will file into an ecology class taught by a chatty zoology professor known — not always out of earshot — as Dr. Doom.

His real name is Eric Pianka, and students enrolled in his Ecology, Evolution and Society course will hear a sad synopsis of Earth’s vanishing species and habitats — coupled with an apocalyptic warning about humans racing obliviously toward the edge of a high cliff.

If he models his lectures on previous ones, Pianka may remark that the planet would be better off without 90 percent of the humans who now populate it — no offense to anyone in particular.

“We should have done something about our population 25 or 30 years ago,” the Denton A. Cooley Centennial Professor of Zoology said during a recent interview at his university office.

“Now we’re going to have to go into a collapse. It’s going to be very painful. The death rate is going to have to exceed the birth rate, we’re going to have famines, civilizations are going to fall apart.”

Such views have turned Pianka, a 67-year-old lizard expert, into one of UT’s biggest public relations headaches.

Terror risk, death threats

It started last spring, when Pianka gave two academic audiences the same doomsday speech he’s been delivering for years. Only this time, a reporter happened to be present and turned Pianka’s remarks into a story in the Seguin Gazette-Enterprise.News services picked it up, the blog world went crazy, and pretty soon, Pianka was being reported to the FBI as a terror threat. The FBI saw no need to launch a formal investigation, but agents did meet with the professor to discuss the death threats that poured in.

Unflattering op-ed pieces and news stories appeared nationwide. The Boston Globe likened him to a “zealot in scientific garb.”

Loved or hated, Pianka is a scientist with stellar credentials who uses his podium to advance ideas that can challenge, enlighten, frighten and offend — sometimes all at once.

In March, just before the headlines erupted, the Texas Academy of Sciencenamed him its Distinguished Scientist for 2006; now the organization won’t comment on his selection or any aspect of the controversy, said its president, David Marsh.

Pianka’s employer has stood behind him. In a sense, Pianka states what many scientists have been saying for decades: Exploding human populations, particularly in developing countries, coupled with voracious consumption patterns in developed ones, put great strain on Earth and its resources, which in turn create conditions ripe for wars, famines and environmental catastrophes.

Pianka might be more blunt than others, said his boss, Robert Jansen, UT’s chairman of Integrative Biology, who called Pianka one of the department’s “most senior faculty members with a long and distinguished career in both research and teaching.”

‘Not politically correct’

It’s Pianka’s willingness to attack all manner of subjects, including organized religion and babies, that lands him in so much trouble.He believes in population limits, lauds China for its one-child policy and says the U.S. government has it all wrong: It should be taxing people for having children, not rewarding them with tax breaks.

Pianka insists he doesn’t advocate the mass killing of people; it’s merely an inevitability.

But, as he writes in The Vanishing Book of Life on Earth, conditions “are going to get better after the collapse because humans won’t be able to decimate the Earth so much.”

“And I actually think the world will be much better off when only 10 percent or 20 percent of us are left. It would give wildlife a chance to recover — we won’t need conservation biologists anymore. Things are going to get better for the denizens of Earth as they deteriorate for humans.”

As an unabashed, unapologetic nature lover, Pianka argues humans should be stewards of the Earth, not conquerors. He takes the biblical book of Genesis to task for encouraging the idea that humans should multiply and have dominion over the land.

In his most cynical moment while interviewed, he described people as “wicked” but quickly added, “Oh, that’s going to get me in trouble.”

“This is not politically correct stuff,” he acknowledged, sitting in the cluttered university office he has worked in for 38 years.

‘It’s all disappearing’

Family members have urged him to just stick to the facts, with no editorials, to separate the science from the philosophy. Pianka’s response: “I can’t separate it.””Humans are at the pinnacle of evolution,” he continued. “We’re at the top of the food chain. We’re able to do anything we want. We can knock down trees, level mountains, distill seawater. A puny man can take a chain saw and cut down a redwood or harpoon a whale. Nothing is inviolate. … It’s all disappearing before our eyes.”

Paul Ehrlich, professor of population studies at Stanford University who in 1968 wrote The Population Bomb, a best-seller that warned of — some say exaggerated — the threats posed by the growth of human numbers, urged Pianka to hang in there.

Ehrlich, too, received his share of nasty letters, harassing phone calls and protests when his book was published. But that year the human population stood at 3.5 billion. With nearly 6.5 billion people now on the planet, the problem is infinitely more relevant, he said.

Opinions on causes differ

C. Herb Ward , who teaches in the department of ecology and evolutionary biology at Rice University , said there is widespread agreement in the scientific community that humans have placed great stress on the natural environment.”Man hasn’t helped the ecology,” he said. “I think most ecologists would say the world is overpopulated.”

But the conclusions one draws from that assessment — whether and how to reduce population growth, who’s to blame for the current state of affairs — are value judgments, Ward said.

They are value judgments Pianka is quite comfortable making.

“I think we’re going to be cavemen again because we’re too stupid to head it off,” he said.

And his are value judgments some are quite comfortable attacking. One critic who attended one of his speeches was quoted in a blog saying it reminded him of a “futuristic science fiction movie with a crazed scientist planning the death of humanity.”

Father Dave Farnum, a priest at the on-campus University Catholic Center, said Pianka’s views don’t mesh with Catholicism, but Farnum wasn’t holding it against him.

“This is a secular university, and God bless America for him being able to speak his mind,” Farnum said.

Not following own advice

For a guy with gloomy views, Pianka is quite pleasant to be around. He is garrulous, quick to offer iced tea to a visitor and eager to show off the 18 bison he keeps as pets on his 184-acre property near Dripping Springs, where he lives alone in a simple stone cottage he built.He has white hair, a full white beard and walks with a slight limp after being gored last spring by one of his buffaloes.

For the record, he’s not advocating people kill themselves for the sake of the planet. And no, he’s not offering his own life, either, as some of his harsher critics have demanded.

“That’s nonsense. I’m just saying the tidal wave is coming,” Pianka said.

One thing about Pianka: He’s no purist. He makes $110,000 a year in his tenured position but donates little or none of it to environmental causes, saying the money would probably be misused.

His two adult daughters, whom he adores, are proof that he did not have himself sterilized as a youth. He drives 70 miles a day back and forth to work, though he does so in a Toyota Prius. He’s got air conditioning throughout his house.

He says he tries to reduce his imprint on the Earth, but not as much as some of his friends, who’ve replaced their cars with bikes. In the end, Pianka said, it doesn’t really matter.

“In truth, it backfires. It’s kind of like crews cleaning up the highways. All it does is encourage people to toss their (trash) out. When you walk or ride a bike or drive a Prius, all you do is encourage some (expletive) out there to drive a Hummer or an Excursion.”

Pianka grew up in Yreka, Calif., in the foothills of Mount Shasta, a few miles south of Oregon. His father worked in the surrounding gold mines and lumber mills. Pianka said he spent every minute he could outside, observing nature and watching the environment deteriorate.

Today, he mourns the disappearance of animals in the Hill Country, where real estate development is rapid. He used to count 18 species of snakes when he bought his property in 1978. He now counts four. Even the rattlesnakes are gone. Lizard species have similarly vanished.

In a third-floor science lecture hall this week, he will share with first- and second-year students a little of what’s been lost. He might tell them humans could have been godlike but instead turned greedy and trampled what they should have left alone. He believes it.