The native red squirrel?shown on the cover of this week’s magazine?is an enchanting animal. Timorous and elusive, its russet coat and tufty ears are now, for anybody in England’s South or Midlands, more familiar from the works of Beatrix Potter than sightings in the wild.

The culprit is the American grey: a larger, constitutionally more robust animal, capable of digesting nuts when they are green, which deprives the more fastidious red of its diet. The red’s territory has shrunk until its southern limit on the English mainland (they still survive on the Isle of Wight) is little short of Hadrian’s Wall. The grey is also threatening the red through disease. Greys are carriers of squirrel pox; it causes them little more discomfort than a common cold does to humans. Red squirrels which are infected die a horrible death. It has been calculated that there are some 140,000 red squirrels in the UK, compared with 2.5 million greys.

It has reached the point where serious action must be taken to save the red squirrel. This is why Country Life made the control of invading, non-native wildlife a demand of its Countryside Manifesto, published earlier this year. The enemy is not only the grey squirrel. Mink which have escaped or been ‘liberated’ from mink farms threaten the existence of ‘dear good old Ratty’, the water vole. In areas from which mink has been eliminated, water vole numbers have recovered.

Muntjac deer, once an ornament in the park at Woburn Abbey, have become a pest, browsing on bluebells, primroses, orchids and young trees. Below the water, zebra mussels from Eastern Europe are capable of causing serious environmental damage, by blocking pipelines. ‘In the Great Ouse, we’ve had cases of boats crashing because their propellers have become so encrusted,’ comments Dr David Aldridge, a zoologist from Cambridge University. In the US, the zebra mussel is said to cost industry £3 billion a year. American signal crayfish, Asian clams and Chinese mitten crabs are all devastating native species. Canada geese are as greedy as flocks of sheep. We forebear to mention vegetable intruders such as the Japanese knotweed, so difficult to eradicate, or even the rhododendron, which has leapt the garden wall to colonise the west coasts of Wales and Scotland.

Concerted action can sometimes contain or remove unwanted mammals. Hedgehogs which predate on the bird life of South Uist are being culled. In the 1980s, MAFF eradicated the coypu?a kind of rodent, bred for its fur ?from East Anglia. A similar campaign should be waged against mink. However much some of us would like to see an end to the grey squirrel, we accept that annihilation is not an option. People who have never seen a red squirrel regard the grey as a friend. But there are other measures that can be taken.

Sterling work is being done by Red Alert North England, run by the

Northumberland Wildlife Trust on behalf of the northern wildlife trusts and their partners. Funding to the tune of £1.1 million has been secured from the Heritage Lottery Fund and elsewhere for the next three years. But spread across 16 reserves in Lancashire, Cumbria and Northumberland, this is not the bonanza it might seem. Further money is urgently needed for research into measures that will contain the greys, control squirrel pox and support the reds.

As vermin, grey squirrels can be shot. Poison bait can be laid under licence where it can be established that they are damaging forestry. There has also been some discussion that, theoretically, squirrels could be neutered through genetic engineering, although it is unlikely that this would be acceptable to the public. But the best means of reducing numbers is thought to be contraception. So far, the only contraceptive method that scientists have developed involves capturing squirrels to administer it. However, as vermin, grey squirrels must be destroyed if they are caught. Research is therefore required into an effective contraception that the greys can take through feed.

It will also be important to understand more about squirrel pox; at present, naturalists do not know if it is transmitted by breath, urine or saliva. We urge Defra to fund this research. Landowners in the north of England can help support the red squirrel by planting silver birch, aspen, hawthorn and other broadleaf trees bearing small seeds (visit www.forestry.gov.uk).