Why doesn't anyone walk anywhere any more?

In the slipstream of the brisk young women who zoom off over the hill to distant jobs each morning, the silky tufts of roadside thistledown are launched upon the air. Stepping out again from a blackberry bush, I resume a walk before breakfast.

The early sun glitters in the hillside rushes and bathes each grazing ewe in its own fleecy aureole. I am filled with happy thoughts of autumn: cool winds and vivid colour; landscape and ocean lit once again for opera.

Never do I feel more solitary as a human being than walking on a Connacht country road. On the shore or the rough hillside, there is at least a sense of natural locomotion, of doing what my species does to get around: the hare has four legs, I have two.

On the road, I lose this feeling of my body being part of nature; I am aware of the gratuitous nature of going somewhere without having to. The day-long emptiness of the road, relieved by the passage of single cars, tractors and the occasional lorry, reminds me how much the rural world has stopped walking.

Flocks of sheep that, 20 years ago, were driven past the gate by a man and a dog now proceed routinely ahead of the farmer's car (the dog, on occasion, riding in the passenger seat). The end of manual turf-cutting, and thus of donkeys and creels, has cancelled a whole seasonal procession between the townlands and the bog. Even a priest out walking with his breviary has vanished from the scene.

He, at least, matched walking with the pace of thought at two or three miles an hour. This was also the rhythm of such Romantic philosophers as Jean-Jacques Rousseau: "I can only meditate when I am walking. When I stop, I cease to think; my mind works only with my legs". Wittgenstein felt the same way, except he was a pacer, up and down (how much inspiration is being sacrificed today for the simple lack of office pacing-space?).

Rousseau, writing in the mid-18th century, stood at the beginning of walking as a conscious cultural act rather than a means to an end. So I am told in an engrossing new book by a young San Francisco woman, living in a city in which more than a thousand walkers are injured by cars every year. Rebecca Solnit's Wanderlust (Verso) is the first general history of walking and she has shown how much we could do with one.

A few years ago, in his massive Landscape and Memory, Simon Schama set out to show that our relationship with landscape and nature has been shaped by cumulative, almost-unconscious references from art and literature. Solnit chronicles how walking in the landscape for its own sake was forged into a fine art in the company of such Romantics as William Wordsworth ("a trailside god") and America's Henry David Thoreau. But at least she doesn't argue, as some post-modernists want to, that all experience of nature must be "a cultural construct".

Wordsworth, at 21, set out to walk 2,000 miles, on the road well ahead of Kerouac. But it was his readiness to take to rough country, even in winter, that launched a new aesthetic of walking. "When we walk," agreed Thoreau, "we naturally go to the fields and woods: what would become of us, in a garden or a mall?" (A mall, in his day, was a sheltered walk or promenade: a Grafton Street without shops).

A century ago, the naturalist Robert Lloyd Praeger walked across-country through most of Ireland, cataloguing plants and where they grew. "There is little," he could say in The Way That I Went (1937), "especially in the agricultural and hill-regions that make up most of the country, to prevent your wandering where you please." Hesitating at a ditch, "a friendly hay-maker in the next meadow will hail you: You'll fin' a footstick down beyant the fince . . ."

Today, when many small farmers seem to associate such intrusion with Europe's designs on the landscape's habitats, a walker can be dogged by fear of interception - a mood which curdles the whole enterprise: a walk, as Thoreau said, is nothing if not the adventure of a free man.

For all its rural antiquity, Ireland lacks the web of old footpaths, bridlepaths, and rights-of-way, often documented and preserved since medieval times, that guarantee a walker's access in countries like England. The rights-of-way created or enshrined in the division of the Irish countryside by the Land Commission are now largely secret to their communities, if not already quietly erased.

The best hope now seems to be a section of REPS (the Rural Environment Protection Scheme) which offers farmers a supplementary grant if they guarantee access to their land by legal agreement with a local development or tourist group.

Some minimal network of local by-ways, clearly marked, would do a lot to restore some amiable feeling to the small-farm countryside, and even to the hinterlands of city suburbs.

Walking, even a mile or two a day, is an act of resistance to an increasingly mechanised world. In a devastating chapter of Wanderlust, Solnit deals with "the disembodiment of everyday life" by mobile machines that make the body redundant, distort the experience of space and time, and blunt all sensory contact with the Earth (the "risk" of showers!). The body is now exercised "as one might walk a dog" using gym machines to simulate the effort of redundant physical work.

If the lack of walking makes our bodies soft, what has it done to our minds? What kind of reality are people relating to, in which distance is confused with time and even the act of walking seems worth faking with a treadmill machine? Here is a mind under siege from dawn to dusk, no longer open to sorting experience or reflecting on it, or to using the body's rhythms to anchor thoughts in a sense of self.

For many Dubliners, a weekend escape to the Wicklows is a necessary reality check, and a new guide from Ashford ecologist Richard Nairn will add to its pleasure and interest. In Discovering Wild Wicklow (Town House and Country House), he brings a naturalist's eye to 18 walks over wonderfully diverse terrain, each with its own community of plants, animals and birds. From the red squirrels of the Devil's Glen to the merlins and kestrels of the Kilcoole marshes, autumn is the time to get out there.