Fred Pearce on the UN Population Revisions

Hi Folks - Back from the wedding and shivaree, and catching up...slowly. Tired and have much farm stuff to catch up on as well, so bear with me one more day.

In the meantime, Fred Pearce has a great essay in Nature on what's wrong with the UN population revisions that anticipate 10+billion by the end of the century. As you'll remember, I'm pretty dubious about the underlying assumptions of the model as well - it doesn't have anything to do with the real constraints we're facing. The Pearce article is well worth a read, even though I don't agree with all of his assumptions about the current trend's inevitable progress.

The latest global population projections, published by the United Nations last week, say that the world will be awash with 10.1 billion people by 2100, a billion more than previously supposed. Already, there is talk again of a ticking population time bomb.

But a closer look at the assumptions behind this scenario shows it to be perverse and contradictory. In fact, it looks more like a political construct than a scientific analysis.

The heart of the problem is this: the new UN estimates record that both world population and global fertility rates are currently slightly lower than presumed when the last projections were made two years ago. Yet, they project significantly higher growth rates than those estimated two years ago.

This paradox is created by a seemingly arbitrary change in assumptions about future fertility that requires a proper explanation. And quickly. Plans to cope with an increasing array of global challenges -- not least climate change and food policy -- are predicated on the UN's demographic projections. The past few years have seen a plethora of scientific papers asking 'can the world feed 9 billion?' It won't be long before the work is revisited to see whether we can feed 10 billion.

We are doing quite well at defusing the population bomb. Women today, on average, have half as many babies as their grandmothers did. World fertility has fallen from 4.9 children per woman in the early 1960s to an expected 2.45 between 2010 and 2015, a projection revised down from the 2.49 figure of two years ago.

The trend is near-universal.

To my mind, the UN uses cornucopian assumptions about what will enable reproductive growth, while Pearce is using similarly cornucopian assumptions about what might lead to a decline - for example, about globalization's ability to support continued urbanization (a question totally apart for the moment from whether continued urbanization is a good thing). But he's right that the UN projections are political, rather than scientific, and I'm glad to see that point raised.

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The 20th century population explosion was possible in large part because of commercial fertilizers (increased food production) and better medical care (fewer deaths at birth, from disease, an older population kept alive), both of which are predicated on the use of petroleum-based products.

Any "study" which ignores peak oil and increase consumption of oil isn't a serious study. Even if we drastically reduced oil use both personal and through international trade, there will still be problems down the road. I'd hazard a guess that we won't be able to feed five billion in 2100, never mind 10 billion.

And I wouldn't doubt the UN "study" doesn't take into account diseases evolving a resistance to drugs. Diseases once thought cured or eradicated could make a comeback (re: swine flu). Without new drugs or the inability to invent new ones, we could see life expectency to return to pre-industrial rates.