Parks and green spaces generate health benefits that would cost more than £34bn if they did not exist, research by Fields in Trust has suggested.
The charity, which protects green spaces, also found that parks save the NHS about £111m a year.
The report coincides with the launch of a five-year plan to protect parks.
Green spaces can improve overall health for all, including "the young, isolated and the vulnerable", said parks and green spaces minister Rishi Sunak.
In the report, Revaluing Parks and Green Spaces, it is calculated that people would need to spend £974 each year to achieve the same level of life satisfaction they get from parks if they were not there.
That individual figure was then multiplied by the adult population, and the findings showed that parks generate more than £34bn of benefits.
The total cost saved by the NHS is based only on prevented GP appointments and does not include savings from non-referrals for treatments and prescriptions.
The research comes at a time when 95% of park professionals say they are concerned about the lack of investment in green spaces, and 16% of people believe their local park is under threat of being built on.
Fields in Trust, which protects more than 2,700 spaces in the UK, has also launched a five-year strategy aimed at bringing 75% of the population within a 10-minute walk of a green space by 2022.
"Our parks are precious and I want to improve access to them for everyone," said Mr Sunak.
"These findings will play an important role in informing how we achieve this goal."