The Big Question: Should animals that have died out in Britain be reintroduced into the wild?

Why are we asking this now?

Environmentalists hope beavers will soon be reintroduced to Scotland, subject to approval by the Scottish Executive. If the trial reintroduction gets the go-ahead three families of European beavers, about 15 to 20 animals, will be brought over from Norway and released into the Knapdale Forest in Mid-Argyll in the spring of 2009. Beavers were hunted to extinction in Scotland in the 16th century for their furs and a secretion, which provided one of the active ingredients in aspirin. Mammals have never been reintroduced into wild in the UK before, though four German beavers were released at a Lancashire nature reserve.

What exactly is reintroduction?

The deliberate release of animals into the wild, usually of species that are either endangered or extinct in a particular eco-system, but have survived elsewhere in the wild. Biologists only realised fairly recently, in the 1980s, that successful reintroduction from captivity needed extremely careful planning, given the skills mammals and birds need to learn in order to survive in the wild.

Why do we want to re-establish beavers?

Despite their absence from Scotland for the past 400 years, beavers are of huge ecological importance to the area and without them there is a gaping hole in the ecosystem. Their ability to create wetland habitat helps other species such as otters, who hunt in the ponds beavers create through building dams; water shrews and water voles, who share their burrows; and even birds, who can feed and nest in the dead wood beavers use in the dams. Damming itself improves river systems by reducing pollutants flowing through the water. Allan Bantick, chairman of the Beaver Trial Steering Group, calls them a "keystone species". A functioning ecosystem," says Bantick, "does not function as well as it might if it doesn't have all the components in place. The beaver has been missing for 400 years too long."

Why do some people oppose it?

An earlier proposal from Scottish National Heritage was turned down in 2005 and Robin Malcolm, the owner of the nearby Duntrune Castle Estate in Kilmartin, among other local residents, has called the present joint bid from the Scottish Wildlife Trust and the Royal Zoological Society "completely irresponsible". Rather than benefiting the local ecosystems, claims Malcolm, the beavers could inflict damage on trees and rivers. A widespread concern is the effect beavers will have on salmon populations. It is a common misconception that they eat fish, when beavers are in fact entirely herbivorous, but fisheries worry their dam building will impede salmon migration. In Norway, where beaver numbers have increased from 100 to 50,000, there has been no detrimental impact on salmon numbers.

Has reintroduction worked elsewhere?

Norway is the best example, but Britain is way behind all of its continental neighbours on reintroducing beavers, because of the bureaucratic quagmire which has slowed down the various proposals in Scotland. Twenty-four European countries have already successfully reinstated the species in their natural habitat. The current proposal is only for a "trial reintroduction", to identify any problems. If they do become a problem, says Bantick: "We've got a good and established hunting culture established in Scotland. This is just another animal that could be assimilated into that regime. That's the way it's treated in pretty much all other European countries."

Have other species been reintroduced?

As yet, no major mammals have ever been reintroduced into the UK, but there have been various successful bird programmes. The white-tailed sea eagle was returned to the Isle of Rum off the western coast of Scotland in 1975 and is now a major tourist attraction, attracting an estimated £2.5m to the Isle of Mull alone annually. reintroductions of the elegant red kite have been successful in various parts of the UK, particularly in the Chilterns. Black grouse numbers are currently rising in the Peak District.

What about in other parts of the world?

The reintroduction of all sorts of species is something of a trend at the moment, though interest tends to focus on the larger and more lovable creatures, or those most in danger of extinction. The International Union for the Conservation of Nature (IUCN) established a specialist group for the reintroduction of endangered species in 1988 which sets up and oversees such programmes all over the world.

Lynx have been successfully transported from Canada to the mountains of Colorado recently, where they had been all but wiped out by trappers. It proved difficult to establish the new lynx community in the United States but after five years there were roughly 40 new animals. If they are still doing well in another 10 years, they will be considered there to stay. Grey wolves have been successfully reintroduced into America's Yellowstone park.

Which species need reintroduction?

Six of the world's eight species of bear are considered "under threat" by the IUCN and high on their list of priorities. The giant panda is an endangered species and only 1 to 2,000 remain in China. Some reintroduction projects are under way, but suffer from a lack of suitable release sites. There have been a number of attempts to reintroduce rhino into the wild in India and parts of Africa, though this is a very fragile process involving tiny numbers.

The Dian Fossey Gorilla Foundation closely monitors groups of mountain gorillas in Rwanda, Uganda and the Democratic Republic of Congo and has attempted several reintroductions, with little success. The snow leopard, native to central and southern Asia, is an endangered species, the most at risk of all the big cats and desperately needs a successful reintroduction scheme in the Himalayas.

So is British wildlife set to change?

It was reported last year that British wildlife experts were asking US colleagues for advice on reintroducing wolves to Scotland. The Wolf Conservation Society is worried Britain is now too crowded for such a scheme to succeed. There have been significant attempts to reintroduce the brown bear to western Europe in recent years, but it is unlikely to be approved here given the bad press the species has received recently: a reintroduction scheme in the Alps ended badly when "Bruno" began misbehaving in Bavaria and was shot in the summer of 2006.

Should we consider wider re-introduction schemes across the UK?

Yes...

* Any species which once existed in the UK and was hunted to extinction is a valuable part of the country's biodiversity

* Re-establishing often distinctive species in an area can be a great boon to the local economy through increased tourism

* It is important, for both scientific and education purposes, that we are able to study animals in their natural habitat in the wild

No...

* Britain is far too overcrowded for the introduction of dangerous mammals such as wolves to be considered

* Our ecosystems have survived for hundreds of years since bears and beavers became extinct here. There's no call to bring them back

* Much of the land in the UK is privately owned. It is unfair to expect individuals to deal with the consequences of any such programmes