Like big kids everywhere, I would love to see it happen. The idea of resurrecting woolly mammoths fires the imagination on all cylinders. Last week interest in this marvellous notion was reignited by Professor Ian Wilmut, the man who cloned Dolly the sheep, ruminated about how it might be done. The answer, in brief, is that it pushes at the very limits of plausibility, but there's a tiny chance that, within 50 years or so, it could just happen.

Even if this minute chance is realised, please don't mistake de-extinction (as the resurrection business is now widely known) for reviving lost faunas and the habitats they used. At best it will produce a public cabinet of curiosities, at worst new pets for billionaires. There is an obvious, fatal but widely overlooked problem with de-extinction. The scarcely credible task of resurrection has to be conducted not once but hundreds of times, in each case using material from a different, implausibly well-preserved specimen of the extinct beast. Otherwise the resulting population will not be genetically viable.

For a species to have a reasonable chance of survival, across decades and centuries, it needs a wide genetic base: composed of a minimum of several hundred individual genomes. The European bison, or wisent, is considered a great success story: it was almost extinct a century ago; now there are 3,000. But it remains acutely vulnerable because the entire population has been bred from the 54 animals to which the species was reduced by 1927. The bison are plagued by problems associated with inbreeding, and a single cattle disease could finish them off, as a small genetic spectrum is less likely than a large one to offer resistance.

Last week the Born Free Foundation doused the excitement over the birth in Chester Zoo of two Sumatran tigers, a species that is critically endangered. It pointed out that the global population in captive breeding programmes is too small to be genetically viable: if tigers become extinct in the wild, they will soon become extinct in captivity.

So the double-page painting published by National Geographic in April, depicting tourists in safari vehicles photographing a herd of Siberian woolly mammoths roaming the Siberian steppes, is pure fantasy: the animals it shows are mumbo-jumbos. And that's a great shame. As experiments by the Russian scientist Sergei Zimov show, mammoths could play a key role in restoring the ecosystems that once supported them. Perhaps 15,000 years ago, hunters using small stone blades moved into the Siberian steppes. Their enhanced technologies allowed them to wipe out the mammoths and most of the musk oxen, bison and horses that grazed there. As a result, the great Siberian grasslands turned to mossy tundra, and have remained that way ever since.

These species sustained their own habitats. They recycled the soil's nutrients through their dung. Their grazing made the grass more productive and prevented it from growing long enough to kill itself. Long grass in Siberia flops over and insulates the soil, which then becomes too cold and wet for grass to grow. It's quickly replaced by moss, which is an excellent insulator, keeping the soil cold enough to prevent the grass from returning. Zimov has shown that when large animals are brought back, their trampling quickly breaks up the fragile layer of moss and lichens, allowing the grass to dominate again within one or two years. The grazers in this habitat, in other words, are keystone species: animals that exert disproportionate impacts on their environment, creating conditions that allow other species to live there.

Many of the large species we have lost performed such roles. They were essential to the survival of the complex ecosystems they dominated. Like the resurrection men, I dream of their return, and the ecological revival that might ensue. But it's not going to happen.

The one or two specimens that even the most ambitious de-extinction programmes will struggle to produce will live and die in zoos. Or, perhaps, in the private collections of the exceedingly rich people who could fund their revival. The bragging rights, admittedly, would be incomparable. "Come and see my woolly mammoth" must be the world's greatest lost chat-up line (though it could be horribly misinterpreted).

Lonely captivity is likely to be the fate of all the animals listed by the Long Now Foundation's Revive and Restore programme as candidate species: passenger pigeons, ivory-billed woodpeckers, dodos, great auks, moas, elephant birds, quaggas, thylacines, Pyrenean ibex, Steller's sea cow, Yangtze river dolphins, mastodons, mammoths and sabre-toothed cats. De-extinction is already attracting plenty of money and expertise. But if the necessary technologies somehow fall into place, sad and temporary exhibits for us to gawp at through the bars are the only likely outcome.

But before you despair, consider this: there are other means of restoring lost ecosystems, thousands of times easier than de-extinction, which could begin almost immediately. Restoring the Asian elephant to parts of its former range, for example (a project that, while the still-dead mammoth gets all the attention, is scarcely ever mentioned) would kickstart some key ecological processes. As large parts of Europe are vacated by farmers, enough land is becoming available to make the revival of Europe's lost megafaunas possible. We could consider bringing back the lions, hyenas and hippos that persist in Africa, and introducing Asian elephants that, while not native here, are closely related to the great straight-tusked elephants that shaped our woodlands.

Does this project not have the same potential to inspire as attempts at de-extinction – and the significant advantage that it can be done?

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• A fully referenced version of this article can be found at Monbiot.com