In Co Clare there's a cave I like to visit: a great big gloomy tunnel descending into the hillside. It doesn't have built-in lighting or tourist guides, but there's nothing very dangerous inside: one requires only a torch and a pair of wellies. It also comes with a legend - it's said to be the place where a long-dead chieftain found his fairy bride.

Eight years ago, I visited this cavern with my girlfriend, in the course of a golden break in the Burren during which she became my fiancee. Things have moved on: last week I left her in the house we were renting nearby and went to the cave with our daughters, aged six and three. The cave lies at the end of a rutted track which runs through fallow fields. We'd asked the lady at the farm where we parked if she owned the land; she didn't, but knew the farmer who did. He wouldn't object to our presence, she said.

We had a delightful trip and, a little muddy, returned along the track. The three-year-old was riding on my shoulders, and I was holding my other child's hand. Then we heard the sound of a tractor and turned to greet the man driving it. In reply we were subjected to a ferocious and terrifying attack.

He didn't actually hit any of us; but when an apparently sane, middle-aged man yells the foulest obscenities in the face of small children, the effect is physically shocking. There was no expletive left unused: mercifully the worst of them passed my daughters by because they were not familiar and his accent confused them. It did not confuse me.

Of course, we had been trespassing, but we had stayed on the track. There was no damage to his property. In the safety of the car, the children cried all the way home.

I know this was an extreme incident: the sort of thing which if it did happen every day, would soon leave Ireland's tourist trade in ruins. Yet it seemed to crystallise a thought which had been taking shape in my mind for much of the preceding fortnight - that the astonishing changes which have overtaken the Republic, and especially its economic boom, are not without their downside.

I don't want to overstate the case: since that first holiday in Clare, my wife and I have returned every year. We will be back. Some people may enjoy spending holidays getting wasted and basted in Greece or Ibiza, but strange to tell, we like nothing better than escaping London's oppressive August heat amid the gales, drizzle and magnificence of Ireland's Atlantic coast.

We love the music, the mountains, the food, the Murphy's. And we also love the people: their unsolicited interest and hospitality; their warmth, culture and charm.

FOR a long time, we've thought they enjoyed seeing us. But for the first time, this summer, we found ourselves wondering if that was the case: and whether the intangible qualities which made Ireland different from anywhere else we've visited were vanishing before our eyes.

In the years since 1989, we'd been to Kerry, to Wicklow, and (several times) to west Cork. But we hadn't been back to Clare, and so the contrast between then and now was all the more noticeable.

In little towns like Corofin, where there used to be one shop open if you were lucky, there's now a bustling High Street, and daily deliveries of items such as fresh French bread. The boom in Ballyvaughan has turned old bars into bijou eateries where you can wash down oysters with Cabernet supplied by the Australian wine-exporting commission next door.

Galway city is unrecognisable, its teeming streets and designer emporiums reminiscent of Covent Garden, even Paris or Rome. And everywhere you go, there is building, building, building: hideous white bungalows, as appropriate to their setting as a tower block, and (more rarely) beautiful new houses which combine traditional materials and striking architectural flair.

But this isn't an article about Ireland's grave need for tighter planning and conservation laws. Nor would I do anything but welcome Ireland's prosperity: from a purely selfish point of view, it has led to a huge improvement in the quality of roads, food and service. It's just that I have this teeny, nagging worry that in getting rich, it might be losing out in other ways. It's difficult to be specific about a feeling like this, difficult to identify incidents whose cumulative effect amounts to a change in atmosphere. But one of the things I did notice this summer, in hamlets as much as bigger towns, was that the people who serve in shops and restaurants have become just like their counterparts in London: not quite rude, but almost; brusque; businesslike; pressed for time; keen to get on to the next customer.

In the not-so-old days, if one went into a shop in Ireland, especially if accompanied by children, one was guaranteed a conversation about coastline and comfort, culture and craic. One would be asked where one was staying; advised about local attractions; invited to join a chat which might, in the course of a fortnight's holiday, blossom into friendship.

This is no longer the case: it is as if the whole of Ireland is in a hurry and, like the White Rabbit, getting increasingly cross about it.

When in Galway we once or twice did fall into conversation. The fact that we were staying in a small hamlet was no longer a cause of pride but a subject of fun: "What's to do there?" And in the little hamlet, the people who ran the local shop knew no more about us at the end our holiday than they had at the beginning, and we no more about them. On the beach there were lots of Irish families doing the things that families do. But here again, in contrast with the recent past where we might end up sharing picnics, they seemed to want to do it on their own. Their children stuck with their own siblings and parents: each family unit surrounded by its own invisible screen.

One DAY we went to the festival at Kinvara, a jolly riot of boat-races, drinking, dancing and live traditional music. It's hard once again to put one's finger on anything tangible. But there was a sense that, as visitors, this wasn't our festival: when our little girl tried to dance with an Irish toddler who was circling in the ring there was a reluctance, it seemed, to smile on them. We could listen and observe if we wanted to, but there were certain boundaries we ought to respect.

I don't think I'm being paranoid, or allowing our experience with the Clare farmer to colour my feelings unfairly. And let me emphasise again: we had a great time, as usual. But I do have a sense that Ireland's soul is subtly changing for the worse.

A Marxist might say that's capitalism: once people get the chance to make serious money, their interest in relationships which are not dependent on the "cash nexus" inevitably declines. Indeed, it's difficult to resist the conclusion that the waning power of Ireland's church is linked to its booming economy - that a people with access to Australian wine in Ballyvaughan have no need of the opium of faith. And I cannot see why a visitor to Ballyvaughan might seek the opium of Irish company when Australian wine is freely available.

I'm not a Marxist, and I hope our next trip to Ireland proves me wrong altogether. But managing the boom means more than building prettier bungalows.

David Rose is a freelance author and journalist writing for The Observer and the BBC.