Nature reserves and national parks are not enough to prevent a catastrophic decline in nature, David Attenborough has told politicians, business leaders and conservationists, saying that every space in Britain from suburban gardens to road verges must be used to help wildlife.

Britain’s leading commentator on wildlife called for a radical new approach to conservation which did not bemoan the past but embraced the changes brought by climate change and a rapidly growing human population.

“Where in 1945 it was thought that the way to solve the problem was to create wildlife parks and nature reserves, that is no longer an option. They are not enough now. The whole countryside should be available for wildlife. The suburban garden, roadside verges ... all must be used”.

Attenborough, speaking at the RSPB’s Conference for Nature in London, said it was now understood that British wildlife was in grave peril of disappearing. “50% of the hedgehog population has gone in 25 years, 90% of the wildlife meadows have disappeared in 100 years; 60% of all wildlife is diminishing and in danger, with 10% doomed to disappear in the next decades. Nowhere in Britain is unsullied, is unaffected by human action. We now have a huge population living cheek by jowl with nature”.

But rather than lament the changes, he urged everyone to act. “We know climate change is happening. It is regretted by some but it is also to be embraced. It is causing great changes in the distribution of animnals and birds in the countryside. We must take advantage of that. It is very important that we accept there are things coming in ... We must recognise that new animals and plants are coming in. Others are moving north. We ought to be giving thought to wildlife corridors ... and not think that every new arrival is to be repelled.

“Because of the complex relationship society has with nature, it is obvious that our response to saving it must extend from every possible quarter too. With an increasing global footprint, mankind is intensifying the crisis for wildlife, but as individuals we can all be part of the solution for saving it too.’’

Watch the full video of Attenborough’s speech at the Conference for Nature

Deputy prime minister Nick Clegg, who will speak at the conference on Wednesday, pledged to keep funding the Royal Botanic Gardens at last year’s levels for a further nine months. The gardens, which are a major tiourist attraction, face a shortfall of around £5m and had their budget cut by £1.5m earlier this year.

Government funding for Kew will now be maintained at the same level as it was for 2013-14, until at least the end of the 2014/15 financial year, said Clegg. “Kew is one of the most important scientific and environmental institutions in the world. That is why I am so pleased to announce that I have secured £1.5m for Kew Gardens until at least April 2015 so its vital work can continue,” he said.

“This is something that I know a lot of people have been campaigning for and is a significant step towards protecting the future of our environment.”

Richard Deverell, director at Kew, said: “We welcome this government recognition of the Royal Botanic Gardens, Kew’s importance and the value of our work. In recent months we have been actively articulating this. This funding will go some way to assist us in achieving the transition to a sustainable future for Kew. However, it will not fully resolve the original £5m gap we identified in our budget for 2014/15 that we have been managing.”

Clegg also announced that the coalition planned to speed up the building of a 2,795 mile national coastal path round England, bringing completion of the project forward from 2030 to 2020.

The move was welcomed by the National Trust, the Ramblers and other countryside groups who had lobbied strongly for the trail for many years but who feared that the project was stalling. Only two short sections have been completed, with work starting recently on several other lengths. Until now, no indication had been given by government about when work might start on many long stretches.

“I’ve been pushing for this process to be speeded up. It hasn’t been easy, but I’m pleased to announce today that the government will be ensuring that the path is completed by 2020 by allocating extra funding,” said Clegg.

“Investing in the coast path is not just good news for walkers, but will help to breathe new life into our coastal towns and villages, boosting tourism and the local economy and reconnecting people with their stretch of coast, helping to promote health and wellbeing,” said Benedict Southworth, chief executive at the Ramblers.

The conference, which attracted politicians from all parties, heard shadow minister for natural environment and fisheries, Barry Gardiner, pledge to protect and enhance the public role of the Forestry Commission and to hold landowners who received large subsidies more accountable by insisting that they worked more for the public good.

He said landowners had worked for their own rather than society’s betterment in the past. “Progress has been opposed by big landowners since 1945. Public access has not led to the destruction of landscape. Increasing access is perfectly compatible with sound management of the environment.”