Tomorrow the U.S. population hits 300 million, and to mark the occasion this week's edition of the Becker-Posner asks the question "Should We Worry About Overpopulation?". Judge Posner provides his number one reason to worry:
The greatest costs of further population increases are likely to be costs external to individual countries and therefore extremely difficult to control by taxation or other methods of pricing "bads," because most of the benefits of these measures would be reaped by other countries. These are environmental costs, mainly global warming and loss of biodiversity, about which I have written at length in my book Catastrophe: Risk and Response (Oxford University Press, 2004)...
If, apart from poor countries, the major costs of population growth are external to the particular nations in which population is growing, there is very little that can be done, given the weakness of international institutions, which is due in turn to the number and diversity of nations that have to be coordinated for effective action against global problems. Moreover, limits on immigration do not reduce global population growth and thus do not respond to the global-warming problem.
Clearly, with per capita income, technologies, and pricing held fixed, greater population would lead to increased congestion and emission of more harmful pollutants. But there is no reason to believe that these variables will be held fixed. Per capita income will be growing, and given my arguments above, perhaps even faster with larger populations. Then the so-called Kuznets environmental curve will kick in. This curve summarizes a well-documented empirical relation that as a country's income begins to grow, at first its environment gets worse. Then, however, the environment gets better as the country spends more on reducing pollutants and has better technologies to do this.
My argument above also suggests that technologies to control pollution are likely to be rising in population, country or worldwide, because the market for these technologies from both the private sector and from governments would expand... while I am not claiming to have disposed of the many legitimate environmental concerns of greater population, I do believe that they are considerably exaggerated by neglecting the Kuznets curve, and the effects of exogenous and induced technological advances.
My instincts are to side with Becker's optimism, but some will be distressed by stories like this one, from the Irish Examiner:
With few exceptions, the world's big industrialised nations are struggling to meet the greenhouse gas reductions they committed to achieve in the embattled Kyoto pact on climate change.
Europe is veering off course, Japan is still far from its target and Canada has given up.
The latest figures are grim news for the agreement's supporters and welcome ammunition for the told-you-so camp in such non-Kyoto nations as the US and Australia.
I'm inclined to the belief that the Kyoto protocol was just poorly conceived, but that still leaves open the challenge posed by Posner: How to implement solutions where no supporting institutions exist?
A loosely related plug: Edward Hugh muses on the trend rate of growth in India, at The Indian Economy Blog.
An unrelated plug: Kash Mansori now has a blog of his very own.
UPDATE: OK, now my plug for Kash's blog is totally related.