"Landscape has become a luxury." So writes David Dimbleby in the catalogue for the new Tate exhibition A Picture of Britain, setting the tone for his accompanying six-part television series on BBC1. It's a perfectly sensible observation, but as the opening gambit in such an ambitious collaboration, it leaves something to be desired. Ever since the Romantics roughed up received ideas of the picturesque, and gave an equal weight to the values of beauty and fear, artists of every kind have tended to agree that "God made the country, and man made the town". Landscape has long been accepted as the place we go to be reminded of what is fundamental in our human natures. We expect it to bolster recovery and provide stability. We assume its beauties are salubrious, and its truths eternal.
Structurally speaking, the show conforms to Dimbleby's amiable model. The pictures are arranged by region, and each is introduced in ways that revive familiar echoes: the north is "the workshop of the world and the wilderness", the Highlands and glens are symbolic of a threatened and then affirmed national identity, the Cotswolds are a pastoral idyll, and the west (especially Wales) is "mystical".
That's all fair enough, and there are plenty of images to prove the point: Lowry's matchstick people, Landseer's Monarch of the Glen, Herbert's Laborare est Orare and David Cox's A Welsh Funeral. Many of these are exceptional, and hanging them together in such profusion will no doubt please the crowds. We see a Britain that is either green and pleasant, made diligent by cottage industries, or befouled by factories. We find people who are either securely at home in their place, or uprooted to a greater or lesser extent. And we follow the presentation of these things from the pre-Romantic to the modern without much variation in terms of point of view, no matter how much we might also notice the evolutions in artistic method and technique.
But here's the problem: the show is more concerned with gratifying existing tastes than it is with making new connections. It doesn't attempt to show how these great pictures might change their meanings in the context of our uniquely configured present.
Our views about the environment, which are so much more anxious than they were even a generation ago, mean that we look on landscape today as something fragile, deserving of our profound respect and care. How can we undo the damage that we've done? How can we safeguard its long-term survival? In the face of such questions, to describe our country visits as merely "a luxury" seems painfully (and potentially destructively) self-centred.
Moreover, it's a concern that triggers other questions, such as those of ownership. New rambling laws are one thing, and welcome. But what about the widening gulf between the way the countryside wants to run itself, and the way that townie law-makers decide how they should go about it? What about the large percentage of the (often non-white) population who feel the countryside is a no-go area? What about the kinds of building that the National Trust and such bodies think are worth saving as "heritage"? (There have been a lot of brave attempts to widen the franchise recently, but there's still a long way to go.)
All these questions converge on another issue, which haunts Tate Britain's show without ever quite coming into focus: how do these pictures fit into our continuing debate about British identity? As far as our past is concerned, they tell us a good deal. The regional structure reminds us that particular areas were indeed held to reflect particular beauties and fears, and yet were often interpreted to conjure a sense of harmony through the whole. The scenes provide an almost infinite variety of responses - ranging from spiritual reflectiveness, through heroic ingenuity and put-upon labour, to complacent possession. But they also assume links between these things. They are an archipelago of views that reflect the geography of the nation.
The greatest painters show all these things at once. Turner, for instance, fizzes from place to place like a Catherine wheel that has broken free of its stake, scattering gold sparks that are sometimes celebrations, sometimes warnings, sometimes transcendencies. Constable, on the other hand, fulfils his ambitions by staying local (he called the Dutch landscape masters he admired "a stay-at-home people, hence their originality"). Quite rightly, he is the hero of the "Flatlands" section, and - also rightly - David Blayney Brown deals in his catalogue essay with the thousands of ways in which Constable is an accurate "natural" painter (all those slimy old posts) and a master elegist. Taking his lead from Gainsborough (especially his great Cornard Wood), Constable seems to show things as they appeared to his eye, while in fact grieving for a just-gone time - for his boyhood, and for the old local order that was associated with his father's business.
The same mixture of "naturalism and contrivance" appears in other paintings of the region and the time - Crome's Mousehold Heath, for instance - but few make the tensions so compelling as they are in Cornfield, or Flatford Mill. (Blayney Brown even conjectures that the hat flung down on the tow path beside the boy and horse in Flatford Mill might belong to Constable's father, who has departed the scene.) As a result, few have the power to reach so powerfully into our modern lives. Their blend of pleasure and regret is a necessary subtlising of Dimbleby's "luxury".
The overarching theme that emerges is of Britain as a multifarious tourist destination. Notwithstanding vigilant stay-at-homes such as Constable himself, the great majority of pictures make us aware that the people painting them are in some sense outsiders - recording what is curious or even spectacular, and relaying them to a distant, sophisticated and often metropolitan audience. Despite the differences in subject and treatment, pictures as different as Girtin's Bamborough Castle, Thomas Jones's The Bard and Rothenstein's Barn at Cherington all satisfy our curiosity at the same time as they appeal to our aesthetic sense and sympathy. Even some of the more industrial (or at least industrious) scenes have the same effect. Joseph Wright's Arkwright's Cotton Mills by Night, for instance, wants to teach its viewer some facts about the industrial revolution they might not know, even as it explores the relationship between natural and manmade forms of power. In this context, a picture such as Sir George Beaumont and Joseph Farrington sketching a Waterfall, by Thomas Hearne, is especially poignant. It shows the two artists encumbered by their hats and wigs and breeches, sheltering under parasols, attended by a servant, and concentrating on the rock-strewn torrent that rushes a few feet from their easels. They are devoted to the scene, entering it with as much relish as they can muster, but bound to seem mere visitors, and therefore to some extent sealed from what they admire.
As we come more nearly up to date, this sense of exclusion grows more elaborate. Paul and John Nash, for example, in their most important mid-20th-century works, both embrace elements of surrealism to give coherent shape to the abstract life inherent in living forms. Part of the purpose is to take us more deeply into a scene, yet as we feel the tug of recognition, we are also held at arm's length.
Paul Nash's Equivalents for the Megaliths is a good case in point. Fuelled by a fascination with the Avebury stones and encouraged by the contemporary work of Graham Sutherland, Frederick Griggs and others, Nash creates a landscape in which flowing chalk hills, the ringed knob of an ancient hill fort, and ageless corn-growing has to accommodate mysterious cylinders, flat planes and a huge blue wedge shape. Is this arrangement a memory of ancient equivalents, a glimpse of future cohesion, or a warning that no such thing can exist? Hearne, crouched under his sunshade, would have marvelled at the ingredients of the picture, but he would have recognised their purpose.
Visitors may regret that they are not more definitely guided to consider such things - and also wonder why there are not more contemporary works, and (possibly) more sporting pictures. There will be plenty of people who suppose that the BBC, or Dimbleby, or both, wanted to duck most of the difficult issues raised by landscape these days, and appeal instead to something retro and feelgood.
On the other hand, provided visitors are willing to make their own footpaths between the pictures, and establish their own connections, they won't be disappointed. There are many great pictures (only 50% of which come from the Tate's own collection), and a multiplicity of themes to establish and explore: the international sources for "Englishness" for example, or the artfulness involved in seeming natural, or why there are so few good pictures of the industrial landscape after the late 18th century.
There is also one very good surprise in the show: some photographs by the East Anglian artist Justin Partyka, which show people at work cutting reeds in Suffolk, or harvesting sugar beet in Norfolk. They look boldly new and yet as old as the hills (except there are no hills in his pictures). The reed-cutter lurches towards the lens with the ear-flaps of his hat hanging loose, creating a powerful sense of what Hopkins called "sheer plod", but also a bewitching richness of reference. He might be a crashed airman, or even a flightless Mercury. If anyone thought the tradition of landscape art was exhausted, as landscape itself continues to vanish under concrete and tyres, these photographs will make them think again.
· A Picture of Britain is at Tate Britain, London SW1, from June 15 to September 4. Details: 020-7887 8888 or www.tate.org.uk/apictureofbritain. David Dimbleby presents A Picture of Britain on BBC1 from June 5.
