In tonight’s IQ2 debate, Professor Steve Keen will be speaking on the “For” team, alongside Dick Smith on the topic “If we keep populating we will perish”: while some wish to grow the nation to spur economic development, others fear that the national population has already exceeded the “carrying capacity” of our land. Should humanity work actively to reduce its numbers, or leave nature to restore the balance? The following is an extract of Professor Keen’s speech.

Two centuries ago, Thomas Malthus argued that the masses faced a future of starvation, because “population, when unchecked, increased in a geometrical ratio; and subsistence for man in an arithmetical ratio”.

We know today that Malthus was wrong. Food production rose geometrically (or rather exponentially) along with population, as technology increased yields.

Malthus’s belief that “the passion between the s-xes will remain nearly in its present state” was also false. In modern parlance, Malthus got his “feedback effect” wrong: rather than rising incomes resulting in more children per family, it resulted in less — from seven per family in Malthus’s day to about two today.

The consequence of these trends was the opposite of what Malthus predicted.  Rather than misery rising, the middle class and mass consumption did — at least in the West.

But what are still called “Malthusian” concerns are still with us today, because of a third factor that did not even figure in his reasoning: the physical limits of planet Earth. Human population today is 10 times what it was when Malthus wrote, and energy use per person is one hundred times as high. While Malthus was wrong about the causes, could Malthus times a thousand be right about the symptoms?

The 1972 Club of Rome Report said so, but as everyone knows, their predictions were wrong too.

Everyone, that is, who hasn’t read the Report itself. Few publications have been as demonised, derided, and misunderstood, as the “Limits to Growth”. For starters, the report concluded that it was possible to have indefinite economic growth. Indefinitely improving living standards weren’t ruled out.

What the report did reject was the possibility of indefinite “laissez-faire” growth — or more accurately, “Devil-May-Care” growth. In reaching that conclusion, they were careful not to make Malthus’s mistake of ignoring feedback effects. The approach they used is known as systems engineering, and while it was novel then, it dominates how engineers design new products today.

They modelled the world as a system with five key factors — population, technology, pollution, food production and resource depletion — where each factor interacted with the others. Rising population depleted resources, for example, but improved technology increased living standards and reduced population growth, thereby reducing the rate of resource depletion. Working from data before 1970, they derived trends in these five factors, and then modelled what this implied could happen in the next 130 years.

Their prediction was that at some time in the early 21st century, food and industrial output per head would peak and then decline; sometime later, pollution would peak and then fall, and by the mid-to-late 21st century, population would also fall. Average living standards would fall back to those of the mid-1800s.

This is the bleak result for which the Limits to Growth is known, but there was also a rosy scenario with average living standards three times higher than those of 1970. So it wasn’t all bad news.

There’s just one catch: their rosy scenario involved achieving zero population growth by the beginning of the 21st century. Unless population growth was, to use Malthus’s word, “checked”, they concluded that ultimately a crisis would occur.

It wouldn’t help merely to reduce pollution, or increase technology, or improve food yields, or even find five or even ten times as many resources as we can currently muster. If we didn’t also deliberately stabilise the human population, then interactions between population, resource depletion and pollution would ultimately do it for us.

Four decades after the Limits report, we’re still a long way from zero population growth. Though some wealthy countries like Japan and Germany have falling numbers, total global population is still growing as quickly as it was in the 1970s. If it continues to grow at this rate, there will be more than ten billion people by the end of the 21st century.

Only there won’t be, according to the Limits argument: feedback effects from the other key global factors will cause an ecological crisis well before then that will cause population to plummet.

This pessimistic conclusion is something that the anti-carbon tax lobby would doubtless reject, but ironically it has a sting for the pro-carbon tax lobby as well. The raison d’etre of a carbon tax is to prevent a crisis caused by rising pollution, but the feedback analysis in Limits argues that this isn’t enough. Unless we also end population growth (and increase food production, and improve technology, and reduce resource depletion), humanity will still experience an existential crisis sometime in the 21st century.

Given our failure to control just one of the factors that affects the sustainability of human civilisation, the odds that we’ll control the other four are negligible.

Two and a half centuries later, the Reverend Malthus may have the final, hollow laugh.

*Tonight’s debate is part of the Sydney series of the IQ2 debate, at  City Recital Hall, Angel Place … Professor Steve Keen is Associate Professor of Economics and Finance at the University of Western Sydney. He was one of the handful of economists to warn of the impending great financial crisis as early as December 2005. Keen won the Revere Award for being the economist whose work is most likely to prevent a future financial crisis. His is the author of Debunking Economics.