England's green and pleasant land is in catastrophic decline, with some of its most precious wildlife at risk of disappearing for ever, the first comprehensive report into the nation's natural life has shown.

In a landmark study into every aspect of the environment, the government advisory body Natural England has compiled research from all corners of the countryside, from woodland and wetland to marine life and salt marsh. Its findings make for bleak reading. Under siege from climate change, development, pollution and aggressive new farming methods, the country's biodiversity is already significantly less rich than it was 50 years ago, The State of The Environment report said.

Just 3 per cent of grassland is rich in native plants and a fifth of the countryside is already showing visible signs of neglect, it reported. The collapse of this habitat is having such a devastating effect on native species, including the red squirrel, the turtle dove, the bumblebee and the adder.

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"If we don't act now, there's a real danger some of our most precious wildlife will be lost for ever and our lives will be poorer for it", said Helen Phillips, chief executive of Natural England.

Conservation charities echoed her appeal, saying they hoped the report would be a springboard for government action. "This is a timely and hard-hitting call which the Government must heed and act upon," said Sue Armstrong Brown, the RSPB's head of countryside conservation. "We are now seeing the consequences of decades of ignoring environmental limits. Now, with the climate changing and wildlife crashing worldwide, it is time for a new green leadership. There has never been a time when human action has put so much wildlife in peril. The Government should support Natural England's plans and allocate enough money to put them into place."

The report makes clear that, with government commitment, the gradual decline could be combated and even reversed. Its authors are urging action on a series of recommendations which they say could save the natural environment from destruction. "England needs a new approach to conservation if we are to effectively tackle the modern pressures on land created by climate change and development," said Ms Phillips. "We need to find ways to manage our landscape to create a mosaic of uses so that we can help our wildlife survive – be it through new 'national park' around the length of England's coastline, better use of the green belt or improved use of public funding for farmers to deliver a better natural environment."

There are already signs that, with the right level of focus and funding, these schemes can work, with the notable success stories of reintroduced species such as the red kite, the large blue butterfly and the pool frog cited as evidence for the merit of long-term projects.

Numbers of native woodland butterflies species have declined by 50 per cent in 10 years, and their demise is all the more worrying as they are an indicator group – meaning that, as they respond quickly to changes in their environment, they act as a litmus test for the health of the natural world. Natural England has suggested that a return to traditional woodland management might tackle the fall in numbers. By using coppicing – the regular culling of smaller trees – the flowering plants they rely upon will be given the chance to thrive again.

The management of wetlands and salt marshes has also been analysed in the report, where native species are suffering similarly catastrophic falls. A major decline in wading birds native to unprotected wetlands has been identified, with, for example, the number of snipes down by 90 per cent. Agricultural and urban development has drained the soil in some areas, leaving it too dry for them to survive. However, by preventing further drainage, and reinstating raised water levels, this trend can be reversed.

Natural England has drawn up a manifesto of measures that it believes can change the fate of the countryside. It hasput tackling climate change at the top of its spending agenda for the £2.9bn of public money allocated to its cause. To carry this out, it plans to prioritise locking-in carbon, absorbing excess rainwater to prevent flooding and connecting wildlife sites. It will also be helping the Government find space for renewable energy by publishing a map of suitable locations for onshore wind farms.

Another key element of itscarbon plan is improved maintenance of upland areas, 29 per cent of which are now in an unfavourable condition. Peat – indigenous to such areas – absorbs more than half of the UK's carbon. But its properties are lost when it dries out, so Natural England has suggested avoiding upland draining and over-grazing in the regions to which it is native.

The Environment Secretary, Hilary Benn, said he believed the right measures, such as the planned investment of £2.9bn in agri-environment schemes over the next five years, could make a difference. "We also now recognise that climate change is presenting us with a new challenge in conserving biodiversity and managing our landscapes," he said. "We need new approaches to conservation, and we are working closely with Natural England to develop these."

But this has done little to reassure environmental campaign groups such as Friends of the Earth, who want a more fundamental overhaul of government policy. The group's campaigns co-ordinator, Paul de Zylva, said: "The Government must do more to safeguard our future. Green speeches are not enough – we need urgent action.

"Ministers must put the environment at the heart of all their policies – including transport, the economy, housing and planning – and invest in clean, green solutions that would make Britain a world leader in developing a low-carbon economy."

The key areas

*Woodland

Butterflies have declined by 50 per cent. The problem is particularly acute in the south of England.

What can be done?

Bring back traditional coppicing, regular felling of smaller trees to create open ground for flowers that butterflies rely on.

*Wetland

The snipe population is down 90 per cent in the Midlands and the South. Its habitat has been destroyed by over-draining from agriculture and construction.

What can be done?

Stop further drainage and restore water levels.

*Salt marsh

This is disappearing at an annual rate of 1 per cent, partly as walls are built to combat rising sea levels. Cord-grass is now found in only three sites in England.

What can be done?

"Managed retreat", where breaks are made in sea defences to let some land flood naturally.

*Arable

Monocultures and industrial farming have affected native species such as the cornflower. In 1960 there were 263 areas of 10 sq km with cornflowers. By 1985 it was less than 10. Now there is only one self-sustaining wild population.

What can be done?

As the flowers traditionally grow around cereal fields, a return to simpler cultivation practices, using lower chemical inputs and not cultivating to the edges, would give them a chance to thrive.

*Marine

Aggressive fishing is affecting not only fish stocks but also other marine life, such as the

pink sea fan, which is threatened by scallop dredging.

What can be done?

More sustainable fisheries management and an end to destructive dredging methods.

*Uplands

The drying of blanket bog could be catastrophic to the amount of carbon released into the atmosphere.

What can be done?

Reduce overgrazing, inappropriate burning and drainage.