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. They had little idea 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.

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 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 with chainsaws. 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. 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, it is hoped they will produce calves. 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 from a respectful distance.

Other animals which treat landscape in the same way will 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.

Rewilding has many supporters, including 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.

In The Spectator, Harry Mount argues against "the misguided Manichean view that nature is beautiful and anything done by man is ugly".

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.