In its latest work on the relationship between green space and health, Natural England estimates savings of £2.1bn a year through improving green space.
The figures follow the launch of its Natural Health Service campaign last month (HW, 31 July).
A key part of the campaign is the Walking for Health initiative (formerly known as WHI), which has been expanded by Natural England and the Department of Health to provide £11.3m investment for the next three years.
Through this scheme alone, Natural England has calculated that around £81m could be saved by the health service.
The report - An estimate of the economic and health value and cost effectiveness of the expanded WHI scheme 2009 - notes that for every £1 invested in the programme, £7.18 of health benefit is delivered.
Author Dave Stone, a specialist in environment and human health, explained: "People who perceive easy access to safe green spaces report higher green-space use, more regular physical activity and lower risk of obesity.
"Therefore, access to safe and convenient green space is likely to be an important environmental factor in public health efforts aimed to promote physical activity and reduce obesity."
The costings are likely to provide a significant evidence base for lobbyists to argue for investment in quality parks and green spaces.
Endorsement from Defra secretary Hilary Benn could also prove positive. "Green spaces are good for us," he said during the launch of the Natural Health Service last month.
According to CABE Space head of public space Peter Neal, the savings could be even greater than those set out by Natural England.
"It is really encouraging to see more work done in this area because it is difficult to get hard empirical evidence," he said. "But if one starts looking more broadly at a radical urban greening programme, there could be significant greater health benefits.
"For example, greater tree coverage and green areas can improve air quality, which could tackle childhood asthma, which is not ad-dressed directly in this work."
The Natural England work builds on a similar scheme run by the National Trust and promoted in its 2008 Nature's Capital report.
That study points out there are significant cost savings for Primary Care Trusts in recognising green exercise and highlights projects such as a health walk at Clumber Park, in Nottinghamshire, supported by Doncaster & Bassetlaw Primary Care Trust and Bassetlaw District Council.
Parks campaigner Alan Barber told HW the latest figures helped provide evidence to the Government of the value of investment in green spaces, but added that quality was important. He said: "It is no good simply to say access to green space is good for health, whatever its condition, features or facilities.
"The Government will accept the argument because they don't need to do anything. However, Natural England has got its foot in the door and should be able to persuade secretary of state for health Andy Burnham."
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