Beware of simple solutions to complex problems. That is a crucial lesson from history; a lesson that intelligent people in every age keep failing to learn.
Later today (Thursday), a group of people who call themselves Ecomodernists launch their manifesto in the UK. The media loves them, not least because some of what they say chimes with dominant political and economic narratives. So you will doubtless be hearing a lot about them.
Their treatises are worth reading. In some important respects they are either right or at least wrong in an interesting way. In other respects … well, I will come to that in a moment.
With the help of science, technology and development, they maintain, human impacts on the natural world can be decoupled from economic activity. People can "increase their standard of living while doing less damage to the environment." By intensifying our impacts in some places, other places can be spared. Through reduced population growth, the saturation of demand among prosperous consumers and improved technological efficiency, we can become both rich and green.
There seems to be some evidence that such transitions could be taking place. In the UK, for example, Chris Goodall, drawing on government figures for raw material consumption, has proposed that we might have reached "peak stuff". Despite the resumption of economic growth, we appear to be using fewer material goods.
I don't dismiss the possibility that this represents a real transition. But in the same period (2000 — 2012), incomes have stagnated while the cost of rents and mortgages has rocketed. Perhaps we simply have less spare money than we had before. If so, we can expect the shift to last for only as long as extreme inequality and an economy dominated by rentiers persist. Admittedly, to judge by the way things are going, this might be quite a long time.
And even if it is correct, can the living world weather this trajectory? If, as the manifesto anticipates, all the world's people follow this presumed curve — their consumption rising until it matches ours, before it peaks and falls — the load imposed on the planet's living systems before the expected transition occurs is likely to be horrendous.
So far, so interesting. In these respects ecomodernism is challenging, provocative and a useful part of the cut and thrust of environmental debate. But then this polite (if utopian) vision takes a dramatic swerve. It's not just that economic activity should be decoupled from human impacts. Human beings should be decoupled from the land, through a massive and rapid urbanisation.
Of course, such processes are happening anyway, but the ecomodernists make it clear that they would wish away almost the entire rural population of the developing world. The US trajectory is the ideal to which they aspire: "Roughly half the US population worked the land in 1880. Today, less than 2 percent does."
This hope appears to be informed by a crashing misconception. The ecomodernists talk of "unproductive, small-scale farming" and claim that "urbanization and agricultural intensification go hand in hand." In other words, they appear to believe that smallholders, working the land in large numbers, produce lower yields than large farms.
But since Amartya Sen's groundbreaking work in 1962, hundreds of papers in the academic literature demonstrate the opposite: that there is an inverse relationship between the size of farms and the crops they produce. The smaller they are, on average, the greater the yield per hectare.
The most likely reason appears to be that small farmers and their families apply a lot more labour per hectare than large farmers do. The ecomodernists seem to have confused low labour productivity with low land productivity; a major and highly consequential mistake. From the ecological point of view, the metric that counts is land productivity: the less land you require to produce a given quantity of crops, the better.
In areas with little work, low labour productivity isn't necessarily a bad thing either, as it ensures that large numbers of people are employed, even though the pay is often very poor.
So what happens to those who were working in "unproductive, small-scale farming"? The manifesto prescribes the following: