In A Line Made by Walking (1967), a work made at the age of 22, Richard Long changed our notion of sculpture and gave new meaning to an activity as old as man himself. Nothing in the history of art quite prepares us for the originality of his action. It is personal yet abstract, gestural yet conforming to the most basic of marks, set in rural England yet somehow universal and speaking to the world.
In the subsequent decades, Long has been exploring the implications of that first work, steadily but almost imperceptibly extending the range and method of his practice. It is only in an exhibition as extensive as this that we can begin to appreciate just how broad and deep his subject has become.
Richard Long has been walking for 40 years, touching the earth lightly, and rarely crossing an earlier path. The realignment of scattered stones, the rearrangement of timber or brushwood found in the landscape, a path trodden in the dust, or water poured on a rock, are signs of a human intervention, often in a timeless wilderness. However, his sculpture in a landscape is not an end in itself. It is recorded in a photograph – which is a testament to his presence, but also an image that stands for the whole experience of a walk.
The making of the sculpture may occupy only half an hour within a walk that lasts for days or weeks. Familiarity with his work has encouraged us to accept this rather unusual convention. However, questions remain. Why do we accept a photograph of a sculpture made in the landscape as a surrogate for the experience of the whole walk?
We now know from other works, as we did not early on in his career, that Long often records the conditions of wind, sound and light and observes incidental details which catch his eye as he walks. If he records these in notebooks, none has ever been exhibited. If he memorises, how does he remember the sequence and how are the lists pared down and edited on his return?
The more we think about the form of his activity, the more we realise how many decisions he makes in realising each work. Every piece is the product of a very deliberate series of choices: the location, duration, length and season of the walk, the "rules" that he sets himself, the choice of words, texts and indeed the decision to make a cross here, a line there or a circle in another place. Are these choices pre-planned or a spontaneous reaction to the circumstances, the view or the mood? Are there several sculptures made on a single walk, only one of which eventually survives as a photograph?
I raise these questions – and there are many more – simply because I want to draw attention to the complexity, depth, nuance and cumulative richness of Long's art. Superficially, the work of recent years may look like the work he was making 40 years ago. However, the very steadiness of his evolution has made it easy for us to overlook the extent of his development.
Long has chosen some awesome places both to traverse and in which to leave a mark, but he has also elevated the significance of places and sights that we take for granted: the crossing place of road and river, the passing of a bird in flight. His observations of the weather, animals and plants encountered on a journey have become a more insistent strain in his work. Occasionally there is an oblique reference to other human activity, but usually Long captures the experience of being alone in a world governed by the passage of the Sun and the cycles of nature.
The compass of man is nevertheless ever-present in his work. The steady endurance of the walker and the sometimes astonishing distances recorded over days and weeks is daunting. We may also observe the way in which Long's own body has gradually become ever more clearly the instrument of his work. The body has always been implicit with its weight and passage expressed through the trodden grass in A Line Made by Walking or the straight path beaten in the dust of the Peruvian desert in Walking a Line in Peru (1972). It is also present in the latent energy of the upright stones placed in numerous uplands worldwide, or in the jagged arrangements of upturned stones seen in some of his recent gallery sculptures.
These are all arrangements of material made by the effort and will of a determined and muscular being. However, the development of Long's wall and floorworks in River Avon mud and Cornish china clay has brought his own physical scale, reach and energy more directly into the work, just as it did for Pollock in his "drip" paintings and Serra in his sculpture Splashing. The simple prints made with the foot and hand have evolved to include a huge repertoire of gestural marks made with a movement and rhythm that extends to the full range of the body. To watch him making a water line in the gallery, or to look at photographs of him splashing mud on a massive wall in movements that are spontaneous within defined co-ordinates, is to view an artist who is totally in tune with his own body, like any highly trained dancer.
Long's work has conventionally been linked to a tradition of English engagement with landscape and nature. But his peers, such as Carl Andre, have always regarded him as an "international" artist, both in his reputation and in his outlook. His work was recognised in exhibitions in museums and galleries abroad well ahead of his first significant shows in England.
Furthermore, Long's journeys across the continents have taken him well beyond the tradition of the genius loci who captures the air and spirit of a given place. No other artist, apart possibly from his friend Hamish Fulton, has roamed quite so wide, recording journeys across uplands, deserts and icy wastes, along streams, rivers, across lakes and from ocean to ocean. The simplicity and economy of his work stands comparison with the marks and elemental sculpture of ancient peoples, but the form, language and meaning of his work is rooted in the contemporary world. His works are timeless in their classic rhythm and beauty, but also particular to this moment. Few artists make us more aware of both the power and the fragility of the earth or, indeed, our own brief passage across its face.
Sir Nicholas Serota is director of the Tate
'Richard Long: Heaven and Earth' is at Tate Britain from 3 June to 6 September. The catalogue accompanying the exhibition edited by Clarrie Wallis (Tate Publishing © Tate 2009), which will feature the extracts, is available £24.99 post-free from 020-7887 8869, firstname.lastname@example.org. Exclusive two-for-one ticket offer for 'Independent' readers. Call 020-7887 8998 and quote "Independent Ticket Offer" until 8 July 2009