AIR quality improvements in Dorset are encouraging rare species of lichen and moss to grow.

Details of the change emerged during a survey in the Gillingham area of North Dorset by the Three Rivers Partnership.

Its work found a total of 108 lichen species and 57 moss species, two of the lichens and one species of moss being in Red Data Lists of endangered species, while one lichen and two mosses were classed as nation-ally scarce.

The survey, funded by a £3.71 million Liveability grant administered by North Dorset District Council and part-funded by the Environment Agency, focused alongside the three rivers that run through Gillingham - the Lodden, the Shreen Water and the Stour.

The survey concluded that there had been a fall in sulphur dioxide levels in the area which had prompted pollution-sensitive species to colon-ise young trees.

Work revealed that these species were noticeably absent from older previously polluted trees.

Species present indicated an increase in levels of ammonia and nitrogen with nitrogen-tolerant species widespread and nitrogen-sensitive species very rare, indicating changes in the area's air quality.

Agency spokeswoman Emma Rothero said: "The results of this survey just indicate what a complex picture biodiversity is.

"We are surprised and pleased to see that the level of sulphur in the local air quality is improving.

"One particularly interesting find is the rare pleurocarpous moss or Blood Moss which was discovered on the silty base of a willow along the Lodden north of Woodwater Farm. The only sites in southern England for this specialised species are in Dorset where it is confined to the upper Stour and its tributaries. Since 1980 it has only been recorded on one site, at Cornford Bridge."

She added that Gillingham town features a number of old man-made structures such as bridges, churches and walls, most of which are built of limestone which is very favourable to both mosses and lichens.

Lichens are best developed on old tombstones in the churchyard and the cemetery, including those made of limestone, granite and marble.

The Liveability grant, which has funded the study, is for the creation, management and use of public open space in North Dorset.