Picture a forest. A Scottish crossbill rummages for conifer cones, a capercaillie fans its tail, a red deer skulks in the shadows, while a beaver gnaws thoughtfully on a tree.

It could be a classic picture of wildlife in Scotland, but for one thing. No beavers. Hunted for their pelts, there have been no wild beavers in the UK since at least the 16th Century.

It can't be ethical to introduce a species which one is then going to kill   Prof Andrew Linzey Animal ethicist

Now two groups in Scotland plan to remedy that. The Scottish Wildlife Trust and the Royal Zoological Society of Scotland have submitted an application to the Scottish minister for the environment to bring back beavers in a small-scale experiment which could lead to a wider reintroduction.

Such "reintroductions" are now a common tactic in the global conservation movement, with plans in the UK to reintroduce wildcats and bring wolves back to Scotland.

The measures are aimed at restoring habitats and providing a more natural path to conservation. Wouldn't it be better to control the deer population in Scotland with wolves, rather than rely on man-made methods, the proponents suggest.

Poetic return

But reintroductions are not without controversy. In mainland Europe, the reintroduction of bears and wolves has met with hostility from farmers worried about livestock being killed.

And there is a key question. Should man attempt to manipulate habitats and eco-systems, even if only to repair the damage done by man in the past?

There is a certain poetry in the return of some animals, something compellingly romantic about a wolf staring cold-eyed out of a snowy forest. And the beaver has its own appeal.

If wolves are reintroduced would hunting them be allowed?

The Scottish Wildlife Trust talks of a "charismatic creature", citing a study which estimates that beaver-tourism could be worth £101 per household.

Regarded as a "keystone" species, beavers will help renew and create wetland which will help "frogs, toads, water voles, dragonflies, birds and fish".

But in Estonia, the return of the beaver has caused problems.

"Beavers have caused floods in forests, which means the forest may perish because of the excessive damp," says Kaarel Roht, senior specialist in the forest department at the Ministry of the Environment.

"Beavers can also close drainage canals with dams to get the food, flooding big areas of land and hindering agriculture."

Culling question

And the solution to this? In 2006, 7,368 beavers were killed in Estonia.

This raises a serious question. Is it acceptable to reintroduce a species which then has to be controlled with culling?

Professor Andrew Linzey, director of the Oxford Centre for Animal Ethics, says no.

BEAVER TRIAL Application for trial in Knapdale Forest, Argyll 15-20 beavers in control zone Trial could start spring 2009 Aim to create more wetland First wild beavers since 1500s

"It can't be ethical to introduce a species which one is then going to kill. Many people who want to reintroduce species don't seem to have an understanding that ecology is an evolving process.

"To reintroduce a species after hundreds of years is to profoundly disturb that ecology. There is no pristine state we can move back to."

But this ethical position is diametrically opposed to that of the conservation fraternity.

Craig Hilton-Taylor, manager of the Red List Unit at the World Conservation Union (IUCN), says culling is sometimes necessary.

Last resort

In Africa, after years of conservation work, including animals being moved to new areas, the elephant population has risen in many countries to the point where culling is seen as necessary by the authorities.

"You want to keep the balance in the system. You have to allow culling... but the thing for us is that it is humane," says Dr Hilton-Taylor.

Accepting culling as a last resort, conservationists focus their efforts on making sure reintroductions are sufficiently well-evaluated that episodes of dramatic overpopulation and animals failing to thrive in areas are kept to a minimum.

Attitudes towards beaver culling would be hard to predict (Picture: Niall Benvie)

"There are lots of reintroductions happening without them being well thought through. Huge amounts of money gets spent on these things," says Dr Hilton-Taylor

"In the case of gharial [Indian crocodile-like reptiles], 10,000 animals had been put back into the wild but the success rate has been appalling, losing them so rapidly."

If beavers should be re-introduced across Scotland or indeed across the whole of the UK, no-one can guarantee that in 20 years they will not have thrived to the point of needing to be culled.

And how the British public will react to the prospect of cute beavers being killed is anybody's guess.

The Confederation of Forest Industries is, needless to say, worried about the prospect of beavers returning, and it questions exactly how "native" beavers can be regarded as in its submission to the beaver consultation exercise.

Profound disturbance

"Due to the interval since beavers were extant in GB (around 400 years) the proposal is in reality one of an introduction of an alien species, and that into a completely different, man-made environment compared to that which existed all those centuries ago."

It is a sentiment that Prof Linzey agrees with.

"It is a big mistake to treat it as though it was a page with holes that have to be filled because they were once filled.

Scottish wildcats must be shown to be a separate species (Picture: Neville Buck)

"An act of introduction is an act of profound disturbance. It needs to be looked at very carefully indeed."

The plans to reintroduce wolves in Scotland could be timed to coincide with the return of beavers, in the hope they would help manage the population. But no-one can say that the wolf and beaver will thrive to the same degree.

And exactly how one chooses to interfere with habitats is a complicated business.

The Aspinall Foundation is working on a plan to reintroduce the native "wildcat" or reinforce a current population, using captive animals. It is said there are still wildcats in Scotland.

But before an application is made, there must be a study of the DNA of the captive animals. If they prove not to be a separate species from the domestic cat, the reintroduction plan will go no further.