The Ramblers – a charity for walkers – has carried out extensive analysis of how footpaths have changed over the past century.
Research from the Ramblers and the New Economics Foundation think tank shows the average postcode in Monmouthshire has 6,800 metres of footpath within a 10-minute walk – the most of anywhere in England and Wales.
The average Welsh postcode has around 3,500 metres of public rights of way within a ten-minute walk.
Public rights of way are paths that anyone has a legal right to use. While these are predominantly used by walkers, they can include bridleways also used by cyclists and horse riders.
In addition, by comparing historical and contemporary maps, the charity has estimated 358 miles of protected footpath has been lost in the former Monmouthshire area since the turn of the 20th century.
However, the charity has warned people across the country are missing out on the benefits of walking in nature.
Jack Cornish, head of paths at the Ramblers, said readily available walking routes can have a "massive impact" on health outcomes.
However, he warned these currently benefit "the old, the healthy, the wealthy and the white", while those in more deprived areas have far less access to nature.
The charity has further called for a £650 million investment in paths across England and Wales – which they say could pay dividends in improving the nation's health.
In total, nearly 50,000 miles of public right of way have been lost over the past century.
In recent years, the Welsh Government has been exploring the possibilities of "social prescribing", where patients are prescribed activities including walking and cycling, as an alternative or alongside medication.
The practice has been touted as a new way to improve physical and mental wellbeing.
Figures from the Welsh Government show around half of people walked more than 10 minutes to get somewhere each week in 2022-23 – down from 60% in 2019-20.
A spokesperson for the Department for the Environment, Food and Rural Affairs said: "We are committed to increasing access to nature and our Environmental Improvement Plan sets out our ambition for every household to be within a 15-minute walk of a green or blue space."
"We are working to reduce other barriers preventing people from accessing green and blue spaces, including through our £14.5 million ‘Access for All’ programme which includes a package of targeted measures to make our protected landscapes, national trails and wider countryside more accessible for all communities," they added.