This last, lonely walker was imagined by science-fiction writer Ray Bradbury, in a dim future when walking is forbidden and pedestrians are considered criminals. His 1951 short story The Pedestrian depicts a misty evening when Mead is arrested by police for just walking – with no particular purpose or destination in mind. "Walking for air. Walking to see," he says, before being locked inside the sinister-sounding "Psychiatric Centre for Research on Regressive Tendencies".

Bradbury's story was set in 2053 and seems aeons away from our own time. But already, people who walk are relative curiosities. Less than one in five Australians aged 15 and over walked for exercise in 2013-14 – the latest available ABS figures – down from 24 per cent in 2011-12 (even then, it remained our most popular physical recreation activity). The number of walkers dropped by more than 700,000 over that time – from about 4.2 million to 3.5 million.

While we might still walk short distances to the bus stop and train station, the notion of walking for sheer pleasure is emerging as something strange or startling. Committed walkers such as Tara Wells, of Caringbah, in Sydney's south, are increasingly thin on the ground.

"People have become disconnected to walking for the sake of it, possibly because of laziness and apathy," she says. "These days, it is easy to go your air-conditioned house to your air-conditioned car to your air-conditioned workplace and not even notice what you've been missing because your life is so full otherwise.

"When I take the time to get out there at the pace of the walker,  I feel much more connected to myself, the people around me and the world in which we are living."

Walking is in decline worldwide. The proportion of young Australians who walk, ride or scoot to school dropped 42 per cent between 1971 and 2013, according to Active Healthy Kids Australia. In the United States, there has been a comparative long-term slide of 35 per cent in school children taking "active transport" – it's similarly down 23 per cent in the United Kingdom and 12 per cent in Canada.

Walking has suffered most in countries that are heavily reliant on cars. Passenger vehicle ownership in Australia increased from 153 cars per 1000 people in 1955 to 568 in 2013. Multibillion-dollar road projects such as Sydney's WestConnex and Melbourne's Western Distributor toll road plan, reinforce the sense that cars are the way to go.

Witness the queues of cars at school drop-off and pick-up zones, or the traffic jams in suburban streets on Saturday mornings. Walking is regarded as dead or wasted time in an otherwise busy day. Walking is something older people do. Even the word "pedestrian" designates it as dull and uninspired.

When we do walk, it's typically to the bus stop, train station or car parking station, often while staring at mobile phone screens. For many of us, the notion of walking for pure pleasure might as well be sci-fi.

Dr Lina Engelen, a research fellow at the Sydney Medical School, within the University of Sydney, recalls regularly walking to school and sporting activities as a child. Parents today are less likely to let children roam free, she says. "We are getting busier and we don't really have time to walk kids to school or to different places," she says.

"And that combines with the idea of our society getting less safe, which it isn't. Fear mongering means people don't let their kids walk themselves and will drive them."

Active Healthy Kids Australia, a collaboration among researchers in physical activity and health, says children used to enjoy a much larger "roaming radius". The group's 2015 report card on active transport – which gave Australia a middling mark of "C" – cited a UK study that children were failing to venture much further than their front yard. The typical distance that an eight-year-old navigates on their own by foot or bike has declined dramatically: from more than 9.5 kilometres in 1919, to 1.6km in 1950, 800 metres in 1979 and 270m in 2007.

The report's authors attributed the growing reliance on cars, in part, to an increase in the distances children travel to school – due to urban sprawl and the preference for private schools over local public schools. But they questioned parents' concerns about stranger danger and road safety – noting that children are more likely to be harmed by someone they know and that rates of pedestrian accidents are low and getting lower.

The slow demise of walking goes beyond the schoolyard. Driving is the dominant mode of transport to work or full-time study for the vast majority of Australian adults. The percentage of adults who instead walked fell from 4.4 per cent in 2000 to 3.8 per cent in 2012, according to the ABS.

Engelen says while the trend of wearing activity trackers, such as Fitbits, may have increased rates of recreational walking, overall "discretionary" walking has been falling for decades – particularly those incidental, short trips to the supermarket, bank or soccer practice.

Many people simply prefer not to walk, she says. "It is seen as just easier and more comfortable to get in the car, especially if it's a rainy or cold day.

"And perhaps walking is not considered as cool as other forms of physical activity. People are more keen to say that they do scuba diving or are training for a triathlon – something that would impress people a bit more than saying 'I walk'. Anyone can do it, so you are not so special."

'It shouldn't be a big deal that you have gone for a walk'

The winter sun is high above Cronulla Beach, in Sydney's south, where even the dogs are blonde. Young mums in bikinis drag double prams across the sand. Leathery men stick mobile phones down their budgie smugglers.

Tara Wells walks by in jeans and pink Converse shoes. She's no Leonard Mead – there are plenty of people out walking today but they're mostly dressed in active wear, intent on working up a sweat.

Wells, 39, has three children under four and finds scant time to exercise. She prefers "incidental walking" – to train stations, the shops or the library. She spent her honeymoon with husband Ian, who runs Sydney Coast Walks tours, walking most of the way from Manly to Bondi.

That's an unusual honeymoon, I say. "Yes," she says.

In 2010, after suffering sudden onset rheumatoid arthritis, she could barely walk and recalls standing at the bottom of a busy train station escalator in anger. "All these people had two perfectly good legs and I couldn't understand why they weren't using them," she says. "I think it's laziness and apathy. I knew that once I got my health under control, which it is now, I would never take my legs for granted."

She says that walking "recharges" her body and mind. "It gets the blood flowing and I feel more connected to myself and to the world. When I walk I can feel the ground under my feet, I can feel the blood pumping through my veins, I can feel the wind through my hair. And all of that helps me remember who I am, rather than just my role as a mum."

Conversations flow better when you're walking, she says. And so we stroll along the foreshore, talking about walking and children and walking with children. We're overtaken by people hurrying by with small dogs – including one in a hi-vis dog jacket.

"What's been lost along the way is just walking for the hell of it," Wells says, watching them go. "It shouldn't be a big deal that you have gone for a walk. I think we have forgotten how easy it is and what your legs are there to do, if only we would use them."

'A way of sharpening up the senses'

Walking is an instinctive process that enhances the body and mind. A Stanford University report in 2014 found walking increases creativity – even when it's on a treadmill. Other studies associate regular walking with a reduced risk of dementia, depression and low self-esteem.

History suggests that an aimless kind of rambling, with no destination or Fitbit tally in mind, seems best for agitating the mind. Poet William Wordsworth is estimated to have walked almost 290,000 kilometres in his life, much of it about England's Lake District. Virginia Woolf sought inspiration while strolling through London's parks. Charles Dickens walked the streets all night, coming home at sunrise.

British writer Geoff Nicholson, author of The Lost Art of Walking, says there's something about the pace of walking and the pace of thinking that go together. Wandering about near his home in the Hollywood Hills helps him to compose novels or solve plot twists. "For me and for a lot of people it is a way of sharpening up the senses," he says. "If you drive down the street, you see things running by the windscreen – they're here, they're gone. But walking helps you see what's there with greater clarity."

Today, Nicholson, 63, has walked up a hill and down again – taking him about 55 minutes in total. He also likes walking in big cities and discovering "strange little corners and alleyways and detours". "Being alone and not needing a car or bus or any other form of transport other than yourself, makes you self-reliant," he says.

Plodding along has some philosophical good, he says. At some point along the long, lonely road, the walker might become the walk – inseparable from the act of putting one foot in front of the other. It's a "zen kind of thing", he says.

"Not wishing to sound too spiritual, there is that sense of belonging, of oneness," he says. "Sometimes I am just a guy trudging along and wishing I was home. But at its best, the body, mind, soul and landscape all come together and raise you up in some way."