THE SUBJECT of this year's always-interesting Oxford Food Symposium, taking place next month, is endangered foods. It is a good subject. Almost all of us can think of foods that were once common and cheap but have become rare and expensive, or that once were grown or raised locally and no longer are in significant quantity.

Food is no different from any other commodity: it moves about seeking a market. And though our eating habits are among the most conservative aspects of our behaviour, they are always subject, at least in relatively rich countries, to influences from abroad. The more pizza eaten, the smaller the market for, say, faggots.

Relatively few ingredients or products disappear completely, though one has to suppose that certain extinct species were, in their day, scoffed with pleasure. (Anyone for dodo?) And to counterbalance the relatively small number of endangered foods are hundreds of relatively new botanical hybrids.

If one is talking of 'dishes', the same is every bit as true. For every recipe that one hardly sees any more, dozens of new ones have entered our repertoire and no doubt will continue to do so. Indeed, few things are healthier in our gastronomical scene than the tendency to 'revive' or 'rediscover' some of the pleasures of the past. As our ears (except for mine) have become accustomed to performances on 'authentic' instruments of the past, so chefs are continually experimenting with dishes created long ago.

Tastes change, and these govern a large part of the behaviour of the food market. The basic difference in my lifetime has been the internationalisation of that market, the relatively stable availability of most produce regardless of season or provenance. This clearly has caused a decline in local production and variety as market gardeners and farms (or fishermen) concentrate on more profitable and more saleable foodstuffs - which is why, for instance, we have fewer eels and more cod.

My own view is that the main cause of 'disappearing' foods is time, whether that required in production or in preparation for consumption. As with most elements in modern culture, the popular option is the quick fix. As I sit here reading about the preparation of olives a la Picholine (named after the brothers who invented the process in the 18th century), which take something like two weeks to reach perfection, it is obvious that fewer people are likely to engage in their production. I did see a barrel of them in my local street market last Friday, but they were notably more expensive than the dozen other kinds of olive.

Similarly, why market real balsamic vinegar, which takes up to 30 years to reach maturity, when a bastard product can be prepared artificially and in much less time?

A hundred years ago people sat down with relish to the three-volume novels of the Rev Sabine Baring-Gould or Edward Bulwer-Lytton, to enjoy the slow unfolding of a violent drama on the Broads or the pomps of ancient Rome and to be taken into another world. And dishes that required prolonged, slow cooking were all very well for houses in which the stove was lit year-round and provided warmth as well as an oven.

Now, messages that are culinary, literary or artistic have to be delivered instantly. Resistance to stews (not just among the young but also among chefs) has been increasing for decades, as has the demand for 'fast' food - not simply burgers but also the '60-minute gourmet fast French food' and, more sinister, meals that are pre- prepared and microwaved.

The time required to absorb and understand a conflict or a concept is, we think, constantly reduced. It is part of the complex of 'an image is worth a thousand words', the culinary equivalent of which is the view that 'a single sharp taste' is worth more than a rich and patient blend of flavours and aromas that must be explored in the palate. Young wine is cheap and good; old wine must be learnt.

I cannot say that this is entirely to be rued. Quickly prepared foods, short, sharp 'takes' have contributed greatly to our repertoire. I do think, however, that we are the losers in the variety department. Among the many reasons why this worries me, beyond the reduction of variety, is that 'slow' foods were the by- product of frugality and of using everything, all parts of the beast as well as the most knobbly carrots that seemed past their prime. Speed is definitely costing us money.

Meanwhile, I would be most grateful to readers if they could inform me of any 'endangered' foods or dishes they have noted. In the age of the revived boar and imported emu, the tendency seems to be towards enlarging our gastronomical variety. But as anyone knows who has failed to notice the absence of a book until it was needed, it is much harder to keep track of what is being lost than what is being gained. I require your help.