Trees

The Whitebeam Family

As many as ten per cent of the world's tree species face extinction, including some found only in the UK. According to new research, three-quarters of all the threatened species have no legal protection.

The most threatened tree species in the UK are all inter-related. Each tree is a clone of another.

Anyone concerned about genetic engineering can relax - these are not products of some geneticist's laboratory. Instead, they exist because of a natural creative process dating back to the ice age.

The trees known as whitebeams are very good at reproducing, but not so clever when it comes to moving around and colonising areas. Because they are copies of their parents they cannot adapt to changing circumstances and locations.

All 11 UK tree species on the list published by the World Wide Fund for Nature, are from the Sorbus group. One such species is the highly rare Ley's Whitebeam, which can only be found in the wild on one hillside in the Brecon Beacons, in Wales.

There are just 16 examples left of this tree, which was probably created shortly after the last ice age, when the Rowan tree and the Rock Whitebeam reproduced.

Nature is not the only reason though - man does not help either.

According to the World Conservation Monitoring Centre's Website showing the full list of trees, quarrying has destroyed some of the sites the species did manage to colonise nearby.

Another endangered species is Sorbus Wilmottiana - or Wilmott's Whitebeam - with only 20 examples managing to live on in the Avon Gorge, where three of the other ten species can also be found including the Bristol variety, whose numbers are slowly growing.

However the Wilmott's variety is causing greater concern. The new World List says there have been recent reports of the illegal collection and cutting down of trees in the gorge, despite attempts to protect the species.

Tony Robinson from English Nature, who works in the area, told BBC Radio 4's Today programme that the whitebeams are actually very good at forming new species.

But it is then that their problems start.

"The Whitebeams are very much trees of open space - rock faces and open slopes.

"Most people know Mountain Ash which is actually a member of the same group as the whitebeams and this grows in very open, mountainous spaces."

He also explained how they can be protected: "What we're trying to do here in the Avon gorge is retain the open spaces, the rocky open cliffs and slopes."

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Woolly Willow

The species is restricted to Arctic and sub-Arctic Eurasia and in the UK is confined to Scotland. In GB woolly willow is classified as Vulnerable. It receives general protection under the Wildlife and Countryside Act 1981.

Woolly willow is one of a number of bushy willows found only in mountain areas. In other parts of the world these willows form high altitude scrub above the tree line but in Britain are usually present only as relict scattered bushes found on ledges inaccessible to grazing animals, on cliffs and in stream gorges. The woolly willow is further restricted by its requirement for calcareous soils.

Vegetation mapping of all upland SSSI in Scotland suggests that 2000 ha of land was occupied by willow scrub with woolly willow before the vegetation was modified by the influence of man. It now occurs in only 12 locations in Scotland. All but one of these populations are very small (less than 100 plants) and four are of single individuals. Willows have separate sexes and so these single bushes are now incapable of regenerating without artificial help. At least two recorded populations have died out since 1950.

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