Syracuse, NY -- Is it later than we think? That's a central question posed by Syracuse University professor Henry Mullins in his new book, "Will Population + Technology = Armageddon?" The earth sciences professor - author of numerous scientific papers - writes for the general public on in studying the potential consequences of runaway population growth. Mullins spoke about his book. (Extended interview)

So what do we worry about, fire or ice?

It could be either. I think we need to worry about excessive population and technology, which promotes more excessive population. In the book, I mention three types of technology: good, bad, and useless. And most of it is useless.



OK. A useless technology?



Twittering. I don't Twitter. Do you Twitter?



No. But celebrities Twitter. If this becomes a best-seller, and you become a celebrity, won't you start Twittering to give fans constant updates on your life?



They'd just be disappointed.



OK. Good technology?



It keeps us alive longer. It decreases infant mortality. It feeds more people. Those are, in most people's minds, good technologies. But if we move past the earth's sustainable limit - what we call the carrying capacity - I'm not certain they're all that good. Population can't just go on increasing forever.

So we might be too smart for ourselves?



Yeah.



Bad technology? Death rays and stuff?



Yeah, H-bombs, A-bombs, biological and chemical weapons - those things.



Is overpopulation the biggest danger?



Yeah. Every ecosystem within the overall earth system has a carrying capacity. It can sustain just so many types of organisms. The earth can only sustain so many human beings. What that number is, I cannot say, nor can anybody else. But at the rate we're going, it looks like we'll pass it. ... Something's got to change.



Any signs we're near carrying capacity?





Yeah. Absolutely. Every ecosystem in the overall earth system has a carrying capacity. It can sustain just so many types of organisms. The earth can only sustain so many human beings. What that number is, I cannot say, nor can anybody else. But at the rate we're going, it looks like we're going to go past it.



In the book, I use the example of a farm pond. The farmer stocks it, catches a lot of fish, and he's happy — until it reaches its carrying capacity and the fishing doesn't improve. So he throws a lot more fish in there, and he comes back, and they're all dead. Because he greatly exceeded the carrying capacity of the pond. It's a simple analogy, but the same thing holds true to our planet. We can't have an infinite number of people.



The growth-curve, over time, is heading in that direction. Something has got to change.



Are there any signs that we're hitting the threshold now of that carrying capacity?



In some countries, we may be. For example, the birthrate for the United States is about 2.1 children for every woman. Any time you're over two, you're going to have an increase. So we're close to equilibrium in the United States. But we're also the most affluent country. I think the worst country on that is Niger — the birthrate per woman is about six. Someone said, when we get to the carrying-capacity, wealth will equalize everything. But we're a very greedy species. We may be an affluent country, but do we want to give half of our salaries to people in Niger, so they can have the same standard of living? I don't think so.

You say with too many of us, the planet will seek a solution. That sounds scary.



That's based on the Gaia hypothesies of James Lovelock. ... When a system gets knocked out of equilibrium, feedback within it brings it back, or the system collapses.

I have three story lines. We exceed the carrying capacity, the earth system adjusts, and we have an equilibrium number of people at our carrying capacity. Everything's fine.

Another possibility is the catastrophe — nuclear winter, or pandemics, or runaway greenhouse effect, whatever. It causes a drastic reduction in our numbers. We go back to pre-industrial times, when we only had a few billion people on the planet.



Worst-case scenario is extinction. Most species before us — about 99.9 percent — are now extinct. We've only been here a short period of geologic time.





That's the catastrophe category?



I have three story lines. We exceed carrying capacity ,and the earth system adjusts, and we have an equilibrium number of people... Everything is fine. Another possibility is the catastrophe story line. Nuclear winter or pandemics or runaway greenhouse or the next ice age -- whatever -- causes a drastic reduction in our numbers. We got back to preindustrial times, when we only had a few billion people on the planet. The worst case scenario is extinction. Most species before us — 99 point nine percent or whatever — are now extinct. And we've only been here for a very short period of geologic time.



Are you an optimist or a pessimist? You're talking some heavy stuff here.



I am. I call it the ultimate question. I consider myself an objective guy: The glass is half empty and half full, if that makes sense. . . I'm looking at this as a scientist.



But what is the "half-full" way of looking at the possibility of a major catastrophe due to overpopulation?

Well, let’s say we have a pandemic like AIDS — and our medical technology can’t handle it. Our numbers come back to the carrying capacity. That’s the equilibrium story line. Life carries on at the carrying capacity level with little variation. When it gets too high, there is negative feedback to bring it back in check. It if gets too low, there is positive feedback to bring it up. So that would be a "half-full" type of perspective.

Won't technology find a solution?



I've had students read the book, and to a person, they put their faith in technology. We're used to rapid technological advances that make our lives easier, and allow for more people to survive birth and live longer. But in my opinion, we're a bit arrogant.



You think we'll live to see it?



I suspect that if there is a correction to be made, it's 50 to 100 years out. But I can't predict the future. Nobody can.



OK, what should we do?



Many respectable scientists and engineers believe we should geo-engineer the earth on a global basis. They would put big reflectors out in space to deflect sunlight, to reduce global warming, or fertilize the oceans to draw down carbon dioxide from the atmosphere. To me, that's arrogant. Life has been on our planet for 3.8 billion years, and it's had many upheavals — plate tectonic collisions, asteroids, volcanic activity. It has always sustained itself in one form or another. Not the same species — but one form or another.



I think it's arrogant for us to think that we have a moral obligation to save life as we know it.My suggestion — it may not be realistic — is that we become a global society, and we recognize that we are heading toward exceeding our carrying capacity, and we humanely reduce our numbers.If things get out of control, there's just too many people.



If our numbers are small enough, we become adaptable. My suggestion is for the United Nations to get the population scientists and the sociologists together and figure out ways to humanely reduce our numbers or level them off at the carrying capacity. ... I consider it all an open question. It's something we need to start thinking about now — not 100 years from now.