By Jonathan Amos BBC News Online science staff

The most comprehensive survey yet of plantlife across the British Isles was published by botanists on Tuesday.

The New Atlas Of The British And Irish Flora details the remarkable changes that have taken place in the countryside since the investigation was last undertaken in the 1950s.

This is not the gloomy story it was 20 years ago David Pearman, atlas editor

It shows how some familiar old species, such as the corn buttercup (Ranunculus arvensis) and burnt orchid (Orchis ustulata), have struggled to cope with the demands placed on them by climate change, modern agricultural practices, and pollution.

In stark contrast, the atlas reveals how tall plants, coastal species and alien invaders, such as the butterfly bush (Buddleja davidii), have often thrived in the altered habitats.

David Pearman, of the Botanical Society of the British Isles, one of the atlas's editors, stressed that not all the changes seen in the 40 years since the previous volume was written had been negative.

Still alarming

"Measures that have been introduced in the last 15 years have improved things. It was a scandal the way the deterioration in the distribution of plants was allowed to continue for so long, but in recent years we have begun to turn the corner," he told BBC News Online.

Corn buttercup: Another struggling to cope (Image by Pater Wakely/English Nature)

"I actually feel quite bullish in particular about the lowlands of Britain which have been undergrazed in the past. The grazing is now coming back and the plants are responding.

"I'm not saying that we don't still lose bogs and habitats to roads and factories, but this is not the gloomy story it was 20 years ago."

Not everyone, however, is prepared to be so positive. English Nature, the UK Government's own wildlife advisory agency, said the declining distribution of some plants was still alarming.

The agency claimed that many plants only held on in some locations because of the protection they received in Sites of Special Scientific Interest (SSSI), nature reserves and other areas in the rest of the protected sites network.

Car pollution

English Nature's botanical expert, Simon Leach, said: "Particularly in the lowlands, these places have become quite literally last refuges for many native wild plants.

"Populations of some of our rarest species - like pennyroyal, fen orchid, water germander and sharp-leaved pondweed - are now almost entirely restricted to SSSIs."

We are in danger of losing that archetypal English countryside with a rich range of flowers and butterflies Prof John Lawton, Nerc

And of great concern are the damaging effects brought on by the rise in the levels of plant nutrients in soils.

Overuse of agrochemicals is partly to blame for driving away species, such as lady's bedstraw (Galium verum) and field bindweed (Convolvulus arvensis), that like infertile soils, but this threat is now compounded by car pollution.

The nitrogen oxides expelled by vehicles are eventually rained out of the atmosphere, raising soil fertility to levels that can be tolerated by a different range of plants - many of which like the common nettle (Urtica dioica) are not very popular with the public.

"Pervasive spread"

Professor John Lawton, chief executive of the Natural Environment Research Council (Nerc), said: "There is as much nitrogen falling out of the air from car exhausts now as farmers put on the land with fertilisers in the 1950s. That is the scale of the problem."

He said the atlas should represent a wake-up call for policymakers on the issue. "We are in danger of losing that archetypal English countryside with a rich range of flowers and butterflies and other interesting insects because of nitrogen deposition from the atmosphere."

Another atlas editor Dr Chris Preston, from the Centre for Ecology and Hydrology (CEH), added: "This is the biggest and most intractable problem.

"It is easy, relatively speaking, to stop grasslands being ploughed up but stopping this all pervasive spread of nutrients is very difficult."

Volunteer army

The atlas took three years to produce.

Among the winners

Coastal species such as Danish scurvygrass (Cochlearia danica) have moved inland with the salting of roads

Its 910 pages and 2,412 maps contain the data collected by 1,600 volunteers, who visited virtually every corner of Britain and Ireland during different seasons to identify and document all the flora found growing outside people's gardens.

Data on nearly 3,000 species are included. The book's editors say it will be the defining botanical resource used to frame environmental policies that affect the UK countryside.

The atlas contains 750 species not listed in the previous volume.

Among the losers

Northern species such as hare's-tail cottongrass (Eriophorum vaginatum) have been pushed back by warmer temperatures

The data are catalogued according to the 3,880 10-by-10-kilometre squares used to by the Ordnance Survey to map Britain and Ireland.

The most species-rich 10-km square was found in Dorset (SY98). The area, which includes the town of Wareham, has an astonishing range of habitats, including heathland, chalkland, lowland rivers and coastline near Poole Harbour.

The atlas project was funded by the Department for Environment, Food and Rual Affairs (Defra), and spearheaded by the Botanical Society of the British Isles (BSBI) and Centre for Ecology and Hydrology (CEH).

The atlas is published through Oxford University Press, priced at �100.00 (hardback with CD-rom).