By Alex Kirby
BBC News Online environment correspondent
Some of England's rich variety of wild plants is disappearing in the face of an onslaught by pollution and invading competitors, the UK Government says.
Cornflowers: Doing well (Image: Peter Wakely/English Nature)
A survey of English biodiversity found plants in trouble in and near fields, along river banks and in woodlands.
But river quality is improving and more of England is being farmed in a way that also respects the environment.
In the UK as a whole, the wild bird population has risen by 5% over the last 10 years, the government says.
The survey report, Measuring Progress: Baseline Assessment, is published by the Department for Environment, Food and Rural Affairs (Defra) as part of its strategy for improving biodiversity in England.
Depending on plants
It notes two negative trends: an increase in nutrient levels (especially phosphates) in rivers, and a decline in wild plant diversity in fields and field margins, river banks and stream sides, and woodlands.
The report says the decline has been most severe in infertile grassland and hedge bottoms. Plants are important food sources for many birds and insects.
Saltmarsh: In trouble (Image: Peter Wakely/English Nature)
Defra scientists say there are several reasons for the plants' plight, including fertiliser use which enriches the soil, and the nutrient enrichment of the rivers. Both can encourage the growth of species which overwhelm less chemical-tolerant plants.
The Environment Minister, Elliot Morley, said: "The key issue for plants is light. If you get invasive species like nettles which shade out the natives, they'll die."
He said one plant, the starry breck lichen which grew in eastern England, appeared to have become extinct in 2002, probably because of airborne pollution.
The chief executive of the Natural Environment Research Council (Nerc), Professor John Lawton, underlined the dangers of this sort of pollution last September.
He 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."
The report says the number of wild birds in England has begun to stabilise after a 20-year decline, with water and wetland birds increasing by 7% since 1975.
Lapwing: Still in decline (Image: Nick Watts/English Nature)
Farmland birds seem to have stabilised since the mid-1990s, and nine species of town and garden birds have increased by 10% since 1979, though sparrow and starling populations have fallen by 60%.
The Royal Society for the Protection of Birds said if the government delivered on the reforms of the European Union's common agricultural policy, the future for birds could be good.
But if it gave the go-ahead to genetically modified (GM) crops, that would be "another kick to farmland birds".
GM trials 'limited'
Last month Lord May, president of the UK's Royal Society, said both opponents and supporters of GM technology had misrepresented the results of the recent trials of their effects on farmland biodiversity, the field scale evaluations (FSEs).
He said: "To generalise and declare 'all GM is bad' or 'all GM is good' for the environment as a result of these experiments is a gross over-simplification, but statements from both sides in the GM propaganda war have claimed 'victory' based on these findings."
Dormouse: Looking better (Image: John Robinson/English Nature)
Mr Morley told BBC News Online: "I think there's some truth in that. People on both sides tried to read more into the FSEs than was there.
"The key finding was what they showed about the impact of chemical management. It was the chemicals that were used on the trial crops that affected the biodiversity, not the GM traits themselves."
Across the UK, Defra says, "the population status of 106 bird species is 13% higher than it was in 1970, although there has been a small increase compared to 2000".
But farmland bird numbers remain at below 60% of their 1970 level, and woodland birds about 20% lower.
The survey was compiled in conjunction with the Royal Society for the Protection of Birds and the British Trust for Ornithology.