Since 1985, Gallup's polling has included a question that reveals a fundamental fact about the relationship between the economy and the environment. Do you agree, Gallup asks, that "protection of the environment should be given priority, even at the risk of curbing economic growth"? Or should economic growth "be given priority, even if the environment suffers to some extent?" Or are they "equally important?" Way back in the Reagan era, 61 per cent of Americans said the environment should get top priority, while 28 per cent put the economy first. Eleven per cent said the environment and the economy are equally important. In 1991, support for making the environment the top priority hit 71 per cent. But the next year it plummeted to 58 per cent. Through the rest of the 1990s, support for the environment crept back up, reaching a peak of 70 per cent in January, 2000. But then it plummeted again, to 57 per cent, a year later. It then slipped further, falling to 47 per cent at the beginning of 2003. But once again it started inching up, reaching a peak of 55 per cent in 2007. Then another slide started. In the most recent poll, conducted March, 2008, it's down to 49 per cent. What makes these results fascinating is how tightly they track the American economy. As the economy surges, stock markets rise, and unemployment falls, support for making the environment the top priority rises. When the recessions hit, stocks tank, and unemployment rises, concern for the environment drops. The big drop from 1991 to 1992? Recession. The drop after January, 2000? The bursting of the tech bubble and, later, another recession. Across the years, the correlation is almost eerily precise. Given the current economic crisis, I'd bet my house that support has fallen to a record low. And no, this isn't a mirage of polling. In the United Kingdom, organic food sales grew by an average 16 per cent a year between 2003 and 2008, as shoppers happily paid more for goods they believed were better for them and the environment. But "in the coming years," research group Mintel warns, "sales are forecast to dramatically slow and growth is unlikely to hit previous levels any time soon." In the United States, the stock price of organic giant Whole Foods reads like a chart of the economy at large: rising from 2001 to 2006, a flat year in 2007, a collapse in 2008. Of course, it's not news to anyone who follows the issue that environmental concern rises and falls in tandem with the economy. Among pollsters, political advisers and environmental activists, it's almost a truism. What this means for environmentalism is also pretty obvious. Green policies require popular support. Popular support requires a thriving economy. Ergo, green policies require a thriving economy. It's not complicated, is it? And yet, environmentalists often show little interest in the health of the economy. Some go further and flatly oppose policies that support economic growth in the belief that growth in almost any form is bad for the environment. Whatever its merits in theory, the anti-growth philosophy ignores the practical realities of getting things done in a modern democracy. You want clean energy technologies? You want green transportation, high-yield sustainable agriculture, and a dozen other sweeping innovations? They all take money and popular support. How do you generate money and popular support? Economic growth. There is no other way. The steady-state economy may be an interesting topic of research. It may be a worthy goal in the future. But it is not relevant today. To see how badly environmentalists hurt themselves by failing to look at problems through an economic lens, consider an issue that is central to environmentalism: population growth. For decades, greens have been warning about over-population. And with good reason. If populations outstrip resources and technological innovation, there will be hell to pay. But in the developed world, fertility rates fell below replacement level -- 2.1 babies per woman -- more than 30 years ago. In Canada, fertility is around 1.6 babies. It is even lower in Japan, Italy, Russia, and other countries, where population decline has begun. Wonderful, say most environmentalists. Fewer people means less consumption and pollution. These nations are lucky. Soon, they will be cleaner and greener. But this ignores the economic effects of rapidly shrinking populations. They are disastrous. The best that can be hoped for is stagnation. At worst, economies will shrink as fast as populations. And that, inevitably, will lead to plummeting concern for the environment. Still, a hard-nosed green might think there's a good tradeoff to be had here: People may care less about the environment, but the population decline will be so beneficial that the overall environmental effect will be positive. Think again. Population size is only one factor in environmental damage. Far more important is behaviour. A small population that lays waste to forests, burns coal with abandon, and merrily dumps all its waste in the nearest river can do far more environmental damage than a large population that finds this barbaric. This isn't theory. The populations of every industrialized country were far smaller 75 and 100 years ago than they are today and yet, in all these countries, most environmental indicators were far worse 75 and 100 years ago than they are today. What changed was economic growth: Growing wealth supported greater environmental concern and we changed how we live. There's every reason to think this process can work in reverse. Which is why smart environmentalists put the economy first.