The human shark destroys its habitat

The 20th century was a fair span for one queen-mother and the merest nano-second in the history of life on earth. But in that 100 years, human activity has whipped up the pace of change into a runaway ecological crisis. Leaving aside the thoughts of Ecclesiastes about the illusion of novelty (nothing new under the sun, etc), the human capacity for messing up the planet is indeed without precedent.

The area of soil now degraded by our species (about two billion hectares, or the area of North America) is actually now bigger than the world's cultivated area. One picks the statement almost at random from the sweep of fact in this remarkable book. It takes the theme pioneered in Clive Ponting's Green History of the World (1991) and updates, elaborates and synthesises it to masterly effect.

For an historian, Professor Neill uses words like experiment and gamble a little too freely, as if there were some racial mind, some evolutionary strategy in charge of our ecological misadventure. But while so much of human destructiveness is casual and blind, there are plenty of notable ecological follies that owe their origins to men (always men) sitting round a table.

The classic of the century had to be the Stalinist catastrophe of the Aral Sea. Arrogantly diverted to the irrigation of cotton-growing, this great lake is now ending as a salt-pan the size of Ireland.

Close behind it, the Aswan dam in Egypt now powers factories to make fertiliser to replace the fertility the Nile floods once delivered for nothing - a choice that China seems doomed to repeat in the damming of the Yangtze.

OFFICIAL policies on migration are helping to decimate the great rainforests of Brazil and Indonesia, official subsidies underpin the progressive exhaustion of wild fish from the oceans. Development banks, lending billions to poor countries, have conspired in all manner of ecological fiascos. Yet we all do that: for every tonne of car manufactured, there are 29 tonnes of waste.

In the context of human guilt it is fitting that the villain of destruction of the ozone layer should have the blank, cloned visage of any US company Vice President/Marketing. In fact, Thomas Midgley was a very clever chemist, but in inventing the first of the chlorofluorocarbons (CFCs), he had more impact on the atmosphere than any other single organism in earth history. Looking at his somewhat pointless portrait (the illustrations in this book are understated, to say the least), one thinks: if it hadn't been him, it would have been somebody else.

From his vantage point in Georgetown University, Professor McNeill teases out some interesting propositions. He suggests that while humankind has enjoyed great biological success on the strength of adapting to change (as has the rat), it has behaved in the 20th century more like the shark, an organism fine-tuned for survival in stable conditions.

For national regimes of all kinds, perpetual economic growth has been a fetish, and while this might work in a world with empty land and unlimited resources, economists have ignored nature - just as ecologists, for the most part, have preferred to ignore humankind.

Those responsible for policy, while acting like conservative sharks, see a regime of perpetual ecological disturbance as normal. In fact, the current situation is an extreme deviation from any of the durable, more normal states of the world over the span of human history. Historians and ecologists, says McNeill, both so skilful at making connections, should get together to sort out our possible futures.

Michael Viney is an author and an Irish Times columnist