Tuesday, July 8, 2014

Climate Misconception #13: Population growth is the underlying problem behind climate change

In my experience, this meme shows up primarily among people who have studied biology, and who mistake human beings for Drosophila.  Yes, under controlled conditions fruit fly populations will increase exponentially until they reach carrying capacity and crash.  It’s a powerful image, and whenever an environmental issue comes up, there will be students of Drosophila, cultured bacteria and other life forms who tell us that, whatever we think the cause is, the real, underlying cause is overpopulation.

For the record, I think there are too many humans on the planet, and I hope population growth stabilizes quickly.  There is certainly pressure on many natural resources because of our numbers, and we displace the habitats of other organisms in our zeal to maximize our exploitation of the planet.  Besides, it would be nice to have more natural areas for solitude and recreation.

But this has little to do with climate change.  The argument is essentially the same as in the previous post concerning economic growth.

We have to systematically reduce fossil fuel use until it hits zero by mid-century.  Isn’t is obvious from simple arithmetic that the key variable has to be carbon consumption per capita and not the number of capita’s?  Short of a mind-bending catastrophe, how can human population fall sufficiently over the coming decades to make a significant dent in greenhouse gas emissions?

In any case, humans aren’t fruit flies.  Throughout history and what we know of prehistory we have regulated our reproduction in various ways.  At this point, the majority of the world’s people live in societies that are at or near the final stage in the demographic transition—low death rate, low birth rate.  There are still hundreds of millions that have yet to arrive, however, and of course they should be encouraged.  The measures that have been shown to work are the extension of education and women’s rights, social welfare programs and economic growth, all of which are desirable in themselves.  Stabilizing the world’s population at, say, eight rather than nine billion people would be a wonderful thing, but at best it could take us only about an eighth of the way toward reaching our carbon goals—and actually a lot less because demographic stabilization is way too slow.

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Michael A. Lewis said...

No, climate change is not caused by human population growth alone.

The impact of human life on the biosphere is a function of the rate of per capita consumption multiplied by population.

We can reduce our impact on the natural world by reducing our population, reducing our consumption, or a combination of both.

In a finite world facing the twin specters of climate change and Peak Oil, it would be wise to choose the combination of population reduction and reduction of consumption that gets us to a steady state economy as soon as possible.

For more information, visit http://steadystate.org

Peter Dorman said...

Michael, I checked out the website you linked to. I couldn't find anything that acknowledges, much less responds to, the points I made in my post. If you think I've missed something, would you care to quote specific text from steadystate.org and specific text from either this post or the previous one? Thanks.

Incidentally, peak oil, if it arrives soon, would be good for the climate.

Michael A. Lewis said...

Hi Peter:

Please read: Population and a Dose of Common Sense, http://steadystate.org/population-and-a-dose-of-common-sense/

Peter Dorman said...

Repeat: could you put a pair of quotes together? I'm asking because I believe it's not possible. If I'm wrong I'd definitely like to know.

Peter Dorman said...

OK, I'll try one more tack. Michael, you're probably a nice guy and I'm giving you a hard time. So let's try this.

First, grant me that, if someone says X is impossible, the onus is on that person to justify it, and not on someone else who says that X is possible. Anything is possible in this universe of ours except for the things that are shown to be impossible. So this means the ball is in your court, OK.

Now here's the situation. You say that permanent economic growth is impossible in a finite world. I say I don't agree. So now it's up to you to give me a reason for why I should be persuaded; just repeating the claim doesn't count.

As part of your strategy, you can poke holes (if you can) in the arguments I gave in my two posts.

Incidentally, no, infinite population growth is not possible on this planet. I accept that, and while I think likely differences in rates of population growth won't have much bearing on whether we come in under our carbon budget, I recognize that population already presses against resources in a general sense, and it would be good to keep further population growth to a minimum.

This is mainly about economic growth and secondarily about the contribution population policy (briefly touched on in the post) can make to climate goals relative to other policies.