Following my last column, in which I sought to stem the distressing tide of disbelief in the very concept of global warming, a frequent (and thoughtful) Camera letter writer responded by saying the real problem is overpopulation and finite resources.

June Warwick wrote that the “column failed to address what to me is a much more pertinent issue. Namely, fossil fuels are a finite entity, whereas the number of Homo sapiens shows no inclination to subside.”

She is, of course, right.

But talking about overpopulation is taboo in many circles. When a New York Times green blogger recently wrote about the connection between climate change and population — the more people there are consuming more resources, the more carbon goes into the atmosphere — Rush Limbaugh, the Grand Dragon of the new GOP himself, decided to weigh in.

“This guy from the New York Times, if he really thinks that humanity is destroying the planet, humanity is destroying the climate, that human beings in their natural existence are going to cause the extinction of life on earth, Andrew Revkin, Mr. Revkin, why don’t you just go kill yourself and help the planet by dying?” Limbaugh said.

Rush’s larger claim may have been to say that environmentalists are hypocrites. But the acidity of his advice to Revkin — go kill yourself — reflects the sensitivity of the topic of overpopulation. Why is it so verboten?

“There is a moral component,” says Boulder’s Al Bartlett, professor emeritus of physics at the University of Colorado and nationally renowned lecturer on the dangers of overpopulation and resource depletion. “It starts with ‘be fruitful and multiply.'”

But that “morality” is a funny one. We live in a society that makes a celebrity out of a woman who has 14 kids by artificial means and views every birth as a joyous one, regardless of the circumstances.

The taboo is, of course, tied up with sex. And government. And the privilege of the Baby Boom generation. How, exactly, should a society go about limiting its birth rate? China’s example of government-enforced birth-rate policy is clearly not the answer, and has led to unforeseen (or perhaps not so) consequences, including female infanticide, selective abortion and a surplus of males. Here in America, we talk with a straight face about the need for families to have more children so that Baby Boomers and the World War II generation can maintain their cushy benefits.

“Social Security is a real problem. It’s not a long-term solution to say we need more young people to pay for us old folks,” Bartlett says. “We have to realize it’s fiscally not sustainable. Eventually we will have to do the obvious: raise the Social Security tax, raise the retirement age or cut benefits.”

But such problems are paltry compared to the big picture: Resources are finite and the more people there are, the faster we will deplete them. A sustainable world population, at today’s U.S. dietary levels, according to David Pimental at Cornell University, is about 2 billion people.

Current world population is approaching 6.8 billion people. We could hit (barring some catastrophic plague or environmental event) 9 billion by 2030 and 11 billion by 2050. That’s not going to work.

“Why would any rational person want to go to 9 billion?” Bartlett asks. “Can you think of any problem on any scale, from the microscopic to the global, whose long-term solution in any demonstrable way is aided, assisted or advanced by having larger populations?”

First, Bartlett says, population never pays for itself. And pipe dreams that technology will save the day are just that.

“High technology is going to be our undoing,” he says, because it has enabled insane levels of population growth.

He points out that, like it or not, oil production will decline (or perhaps is declining) even as demand rises. Fanciful notions that we can extract petroleum from, say, oil shale neglect to take into consideration the enormous energy inputs required to get the stuff out and make it usable.

“I suspect we will see a future marked by rapidly rising costs of fossil fuels,” Bartlett says.

So what then, I asked him, should we do? China’s approach is morally suspect and has resulted in unforeseen consequences (Bartlett likes to quote the late newsman Eric Sevareid, who said, “The chief cause of problems is solutions”). Nobody likes the specter of enforced population control.

In the United States, Bartlett thinks we just need to start talking honestly.

“I think we should have a coast-to-coast debate, led hopefully by the president: How large a population do we want to have? What is sustainable?” Bartlett says. “I think the answer is maybe a half or a third of our present population.

“But we don’t even acknowledge it’s a problem. The last president to be really concerned about this was Richard Nixon,” he says.

In 1972, when Nixon’s Rockefeller Commission took a look at the issue, U.S. population was about 209 million, and the world had some 3.5 billion souls. Today we have 305 million in the United States — just about what the commission, which predicted doubling in 70 years (with a declining birth rate, actually), expected. It’s still too many.

Meanwhile, world population has alarmingly almost doubled since then. And more of those billions than ever, understandably, want a high-consumption lifestyle like yours and mine.

That’s not going to work.

E-mail: claybonnyman@yahoo.com