Getting in touch with nature can help keep people fit, reducing the burden of sickness on the health service, conservation experts say.
Long walks are good for you
Natural England is launching a campaign to get people to spend more time outside among the country's wildlife and natural environment.
It said being close to nature could cut stress and increase physical activity.
The conservation agency said the aim was to help prevent ill-health, such as obesity, rather than treat it.
Natural England health adviser Dr William Bird said: "Increasing evidence suggests that both physical and mental health are improved through contact with nature.
"Yet people are having less contact with nature than at any other time in the past. This has to change."
Dr Bird said children with attention disorders had been shown to improve when they had contact with nature, and people recovering from operations had been shown to need less painkillers if they looked out on to green fields.
He also said people were more likely to keep up regular exercise regimes if they took place in natural settings, rather than in a gym or leisure centre.
The aim of the campaign is to get people to have more contact with the natural environment where they live by promoting green spaces and encouraging health professionals to incorporate them into the advice and care plans they give to patients.
Natural England is working with the BBC and more than 300 partners, including councils and health charities, to promote its campaign, called Breathing Places.
South Downs Way
It will be the first of four campaigns to get people more involved with nature.
Liz Cleaver, controller of learning at the BBC, said: "These campaigns now provide the public with the opportunity for people to get outside and to get actively involved with nature close to where they live.
"That's great for wildlife - but it's also fantastic for everyone's health and well-being."
The campaign has also received support from the government. Dr Fiona Adshead, the England's deputy chief medical officer, said: "I welcome Natural England's commitment to encourage and enable people to make use of the country's outdoor space for physical activity."