The three great animals walked out cautiously into the woods of Wilder Blean in Kent. All had travelled a long way - the matriarchA female leader of a family or community. from the Highland wildlife park in Scotland, the two younger females from Fota IslandA wildlife sanctuary in County Cork. in Ireland. As they lowered their heads to sample the vegetation of their new home, they had little idea that they were part of a visionary new experiment.

"We want Wilder Blean to mark the beginning of a new era for conservation in the UK," said the head of Kent Wildlife Trust, Evan Bowen-Jones. "We need to revolutionise the way we restore natural landscapes, relying less on human intervention and more on natural engineers like bison, boar and beaver."

Many ancient woods in Britain were turned into commercialRun or maintained to make a profit. forests during World War Two. The tall, densely planted pine trees that now dominate Wilder Blean block out sunlight and make it harder for many species to survive. It is hoped that the bison will reverse that.

Bison are a keystone species, meaning that they can maintain an entire habitat. As the biggest land mammalsA male bison can weigh as much as one tonne. in Europe, they can transform woodland more effectively than humans could with chainsaws and heavy machinery. They have been described as "nature's woolly bulldozers".

They can create paths through dense vegetation, killing non-native trees by knocking them down, gnawing away their bark or rubbing against them. By taking dust baths, they create patches of bare earth. They also disperse seeds via their fur and dung.

All this should help plants, insects, birds, bats and lizards thrive. The pines will gradually give way to native oak, holly and silver birch trees, attracting birds like turtle doves and nightingales.

The three female bison will be joined by a male in August, and it is hoped that they will produce calves in the next year or so. They will eventually have over 400 acres of woods to roam, with special "bison tunnels" to take them under public footpaths. Walkers will be able to watch them in safety by keeping a respectful distance.

Other animals which treat landscape in the same way will also be introduced, such as Exmoor poniesNamed after an area of Devon and Somerset where they roam freely., Longhorn cattleAn English breed with horns curving around the face. and iron-age pigsThey actually date from the 1980s, when an ordinary pig was crossed with a wild boar to create something close to an ancient pig..

Wild bison became almost extinct in Europe a century ago, as a result of uncontrolled hunting. They only survived through captive breeding and rewilding in countries like Romania and the Netherlands. Today there are over 7,000 of them: the biggest herd, in Poland, numbers around 1,000.

Rewilding has many supporters, including the singer Ellie Goulding. "The idea that we can reverse biodiversity loss... just by letting everything take its natural course once in a while - is pretty damn cool," she writes in The Guardian.

But not everyone shares her enthusiasm. In The Spectator, Harry Mount argues against "the misguided Manichean view that nature is beautiful and anything done by man is ugly". In fact, he says, "the sublime beauties of the British countryside are almost entirely thanks to man playing around with Mother Nature".

Yes: Nature always knows how best to do things, creating a balance which man has disastrously disrupted. We need to get back to the way things were before humans changed the land through agriculture.   

No: Climate change has gone too far for that. The only answer is to make radical changes to the way we live our lives, put an end to fossil fuels and invest heavily in green technology.

Or... We should manage land everywhere more carefully. Rewilding is great for some places, but we need agriculture - done in a responsible organic way - to maintain the world's food supplies.