SOME of Scotland's oldest native species are among the most threatened plants in our environment, according to the most detailed study of native flora ever made.

An "at risk" list has been drawn up of the 13 most endangered vascular plants after a two-year survey and analysis of the whole of the British flora.

Vascular plants are those that contain vascular tissue such as flowering plants, conifers, ferns or clubmosses.

The study, carried out by botanists from across the UK and Ireland, shows that of the 1756 vascular plants, 345, or 20-per cent, are threatened. Among them are the corn buttercup, which came to Britain with Roman farmers as they introduced new crops such as the opium poppy, peas and beans, and which has now been classified "critically endangered".

The plant's sharpest decline has been in the last 30 years during which the number of square kilometres that it covered dropped by 81-per cent.

The purple milk-vetch, a small perennial herb which grows on sandstone sea cliffs in Scotland, has been classified as "endangered".

Once abundant in chalk soils in the south of England and limestone soils in the northeast of England, it is now mainly confined to the east coast of Scotland down to Lincoln and East Anglia.

Eyebrights, small semiparasitic plants, were once used to treat eye disorders as, according to the doctrine of signatures, plants healed the organ in the body they resembled.

The tiny white flowers of eyebrights, which have suffered serious decline and now cover only 38-per cent of the area they once did, in close-up are blotched with yellow and purple stripes like a bruised eye.

The vascular plant study was carried out by a partnership coordinated by the Joint Nature Conservation Committee, a government agency.

The group was chaired by Lynne Farrell, of Scottish Natural Heritage, who said: "We are losing some of our nice, special things. The new data tells us how things are changing, and it tells us they are changing faster than we think and also that the change is wider-spread across Great Britain than we thought it was.

We've not just looked at the very rare things, we've looked at the whole of British f lora, so all the plants that occur throughout the country were looked at."

Ms Farrell said the decline of so many species was the result of a number of environmental factors working independently.

Habitat loss is a major factor - we've lost many wetlands in particular. Herbicides, buildings and roadworks are also responsible, a lot of the arable land has now gone under concrete.

"Climate change is another factor, but I think we're looking at the beginning of that, so that a lot of our northern species in Scotland may retreat, as it were, higher up the mountain into slightly colder places. And grazing too is also a factor. A lot of our grasslands are overgrazed."

Ms Farrell said it will be difficult to halt the decline of the plants, and added: "The wider implications are that, if we don't have any plants, we won't be able to live and breathe the way we do."

AT RISK

Endangered

Purple milk-vetch

Eyebright Y

ellow bird's nest

Vulnerable

Prickly poppy

Night-flowering catchfly

Holly fern

Dodder

Field gentian

Frog-bit

Henbane

Lesser butterfly-orchid

Mossy saxifrage