People are boobs. At least, you could draw that conclusion from the discussion at the World Summit on Sustainable Development taking place in Johannesburg. In the blind pursuit of "development", man unwittingly damages nature - and his own quality of life. The only open issues are what rate of damage to tolerate and how to manage that damage through public-private co-operation.

This conclusion is true, some of the time. But to accept it wholeheartedly is to ignore that development can sometimes benefit nature, along with man. And occasionally, checking development in the name of nature - limiting growth to "sustainability" - turns out to be boobyheaded as well.

Consider the US's troubling forest fires, some of which continue to rage even as the Johannesburg summiteers convene. President George W. Bush is calling for a return to more intense logging to slow the flames. His critics dismiss his position as pure politics: Republicans crave the vote of logging states - Oregon, Washington and, the fates willing, elusive California.

You could argue, though, that what is politically expedient is also correct, and that more logging can save many millions of acres of woodland. Herewith that argument, pulled together by scholars at Perc, a free-market group in Montana.

At the end of the 19th century, much of the US was forest. But logging was proceeding across the land at a furious pace. Washington was concerned that American forests might experience a version of agricultural Britain's Tragedy of the Commons, when overgrazing turned lush fields into dusty ones, and animal husbandry failed. To forestall a "timber famine" Washington created the Forest Service. That early conservationist, Theodore Roosevelt, helped inspire the project. The idea was to manage tens of millions of acres of public land to rationalise the tree harvest, government contracting with logging companies. The goal was similar to that of the current summit: to make development decisions that yield "the greatest good for the greatest number in the long run".

As now, wildfires were also a concern. A 1910 firestorm originating in the Bitterroot Mountains burned 3m acres in Montana, Idaho and Washington. Its smoke was said to reach as far as New York.

For 50 years, the Forest Service worked conscientiously. In the 1940s, with a national advertising campaign, it created "Smokey the Bear". Smokey's motto became known to every American, thanks to some assiduous pro bono work by the advertising people at Foote, Cone and Belding: "Only you can prevent forest fires". The campaign worked. In the years following Smokey's arrival, fires decreased by 90 per cent.

In the 1970s, 1980s and 1990s, the Forest Service began pursuing a third goal: preserving nature. Logging, especially "clear-cutting" hundreds of acres, was halted. In the famous case of the endangered northern spotted owl, authorities banned clear-cutting on 17m acres in the Pacific northwest to save the bird.

All this did much good: today about a third of the US is forest, the same share as in 1920. Some parts are even more heavily forested than in memory: at the end of the last century about 85 per cent of New Hampshire was covered with forest, compared with only 50 per cent a century earlier.

But these benevolent policies - no fires, no clear-cutting and preserving nature - also laid the ground for great trouble. Unlogged and without periodic natural burns, forests and thickets grew so dense that they became tinderboxes. In the late 1980s, a fire at Yellowstone National Park scorched a third of the park. More recently, there has been a series of fires in Arizona and Montana. In 2000, Bitterroot burned again. This summer millions of acres in Arizona, Colorado and Oregon have been eaten away by fire.

One way we know the fires are partly the result of federal policy, says Roger Sedjo, a forest expert at Resources for the Future, an environmental think-tank, is because so many fires are on public land. The older trees there (public lands are less logged) are simply more susceptible to fire. Private land, where logging is often less restricted, have seen fewer disastrous blazes. So has the Manitou Experimental Forest in Colorado, which was selectively logged to test the "thinning" hypothesis.

By now the problem of overzealous conservation has been generally acknowledged; many players in the forest fire debate now advocate some form of "thinning". But environmen- tal lobbies still oppose cutting to such a degree that they are even stopping thinning. A consortium of public and private entities recently wrote a plan for thinning in the area around Flagstaff, Arizona. But legal appeals by environmental groups have so far blocked the plan; and the area is now highly vulnerable to wildfire.

America's forest saga offers a challenge to the Tragedy of the Commons dictum. The usual lesson drawn from the "tragedy" is that more regulation is necessary. But in the current instance, the tragedy has occurred precisely because of regulation of communal property - national forests - even though that land has been held with the specific aim of preventing the logging equivalent of overgrazing.

The free marketeers' explanation here would be that the Tragedy of the Commons is really about the failure of private-public co-operation, not private greed. And that even a well meaning government agency can be a worse steward than a private sector owner. In other words, all-private ventures can sometimes yield more socially beneficial results than oh-so-popular public-private ventures.

The burning skies of America's west are not visible in Johannesburg. But they are worth calling to mind as planners consider the future development landscape. Sometimes it is not the development but the sustaining that is the problem.

© Copyright 2002 Financial Times