To an astronaut, Planet Earth appears as a vast ocean surrounding a bunch of islands, of which one of the smallest is Bermuda. This Island's first settlers, dreaming of riches to be made in ambergris, whaling, fishing and planting, must have realised as soon as they landed how finite it was, in size as much as in resources. There was no clay for making pipes or pots, no quartz for glass bottles or windowpanes, no metal nor coal to forge tools and guns. Hence Governor Nathaniel Butler's desperate plea, in 1620, to "send Yron and Cole, without which we cannot live (for we cannot live without fish, nor can fish without hookes?.". Economic self-sufficiency, which might be defined as the ability of a country to satisfy all its needs from within its own boundaries, was never an option for this tiny land which, from the very beginning, had to rely on subsidies and trade for survival.

Surprisingly, though, Bermuda ran into the next hurdle ? sustainability ? no more than three decades after colonisation. In 1639, as a result of the drastic depletion of fish, fowl and turtles, the failure of farming, and a rapid increase in population, Bermuda's leaders declared the Island to be "overpopulated in proportion to existing resources", and recommended emigration (the population then stood at fewer than 3,000). Seen as a history of resource use, Bermuda's economy proceeded from exploiting indigenous resources - hunting, fishing and shipbuilding - to trade and piracy, was repeatedly rescued from ruin by interludes of military significance until, in the mid-1800s, farming for export became the mainstay for almost a century. After World War II, tourism took over as the number one earner of foreign exchange, to be in turn eclipsed by offshore business from the 1990s on. Each economic activity left its mark on the Island's landscape, culminating in the galloping urbanisation we have seen over the past few decades. Each phase might have been sustainable in principle, yet each gave way to the next ? with no turning back.

Equivalent in area to Manhattan, Bermuda is now a city-state in the middle of the ocean. Like a city it trades its services to the world at large - international business and tourism - in return for practically everything it needs to survive: hardware, and consumables such as food and energy. The sustainability of such trade depends not only on the price, and on the ability and willingness of the partners to produce and deliver the goods, but also on a multitude of external factors of which, given Bermuda's isolated position, the global political environment is but one. If Manhattan were cut off overnight from the rest of the US, would it be sustainable? And who would suffer most, the city or the country? In spite of what New Yorkers might say it is clear that the city would come crashing down in short order, from food or energy starvation, or waste accumulation, whichever came first. Bermuda, not quite as densely populated but nevertheless carrying at least a hundred times more people now than it could ever sustain by fishing and farming, would be not much better off in such a scenario.

There is another way of looking at economic development, which is the transformation of nature into human tools: trees into hammers and houses, ores into cars and bulldozers, and oil into fuel to power it all ? a vast arsenal of tool sets in the end, from agriculture to fisheries, trade and transportation, medicine and culture ? all of it feeding on natural resources, for the benefit of a single species ? us. With nature as the raw material, such transformation is self-accelerating because the better the tools, and the more of them there are, the more efficient the conversion process becomes, and the faster the economy grows (a bulldozer will change the landscape more rapidly and thoroughly than a shovel). Yet there is good evidence that the price of economic growth is the loss of nature. Some such losses are irreversible, at least on a human time scale ? species extinction is forever, as is the exhaustion of natural resources such as oil. Other losses are gradual, and reversible in principle albeit at a cost; depleted fisheries can recover, and a paved road might conceivably be ploughed up and turned into a forest again ? although this is rarely done.

Each development brings about a narrowing of options for the future. A forest holds - in addition to providing services such as air renewal, water purification and climate control - the potential for many activities: hunting and timber, recreation, development. Once clear-cut for farming, however, its biodiversity is reduced to a single crop species; and once paved over and built upon, the forest has been irrevocably reduced to a single purpose: human habitation. Human tools retain their usefulness only as long as they are applied sustainably; once a resource is used up, tools become scrap. I would argue that a city represents the most sophisticated tool set there is in the human arsenal. (In the recent hurricane disaster in New Orleans, what made the city ultimately uninhabitable was not the loss of buildings but lack of water and food, and the surge of sewage and trash. On the other hand, judging from the ruins of past civilisations in Mesoamerica and Asia, it will take even a fast-growing rain forest more than a thousand years to reclaim a city). Clearly, what concerns me is the spectre of Bermuda's irreversible urbanisation.

Sustainability has been defined as satisfying the needs of today's generation without jeopardising the aspirations of tomorrow's. But can there be prosperity without economic growth, which is tantamount to a loss of nature? And yet: what is the alternative to sustainability ? Hit and run? Slash and burn? We may not come up with perfect answers, but I have no problem with being asked, like everyone else, what kind of Bermuda I want to see in the future. Nor do I have any doubt that most of us will want "better and more" of everything - jobs and leisure, boats and cars, education and pay, homes and a lot of green space around them. We may want less traffic on our roads but still get to work in time and comfort. We may want all the best facilities and services ? health care, sports arenas, container ports, waste disposal and recycling plants ? provided they are not located in our backyard. We may have to re-develop existing tools rather than develop from scratch; and there will need to be trade-offs between the short-term profit of turning all of nature into 'people stuff', and the long-term benefit of leaving enough of it alive and well so it may continue to deliver its vital goods ? clean air and water, biological diversity, space, and beauty.

The quest for sustainability may well be the tallest order that any economy has ever faced, especially one as small, sophisticated and successful as Bermuda has been for over half a century. It has become clear, though, that human business can only thrive in the long term if it is integrated in the larger framework of nature's business, global ecology. There is no shortage of human endeavours, large or small, that have run afoul of resource limitations ? from the ghost towns of the gold rush to crashed island societies such as Easter Island or Nauru. Continued reliance on the "invisible hand" of individual gain to steer one species ? us ? collectively to ever-greater prosperity is, in the face of shrinking resources and mounting environmental woes, nothing less than wishful thinking.

Nor does the "invisible hand" work for other species, for that matter. It seems that nature knows no favourites. I used to be taught that balance reigns supreme in nature: no predator ever extinguishes its prey; no parasite will ever kill its host, and no organism will ever bring about its own demise by abusing its environment. Wrong.

My favourite eye-opener is about puffins. In 1890, more than a quarter million pairs of these funny seabirds that look a bit like parrots were nesting on Grassholm, a 20-acre island off the coast of Wales. At bird densities of 2-3 pairs per square meter, though, the island's vegetation was eventually destroyed, and the soil was so severely eroded that, by 1928, all that was left were isolated tussocks of turf sheltering no more than 200 pairs of puffins. The silly birds had literally wrecked their own island. Thriving on a seemingly limitless supply of fish in the ocean, out there, they had succumbed to a serious bottleneck at home.

Is there a lesson to be learned?

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