Considering that Scottish landscape artist Andy Goldsworthy deliberately creates artwork out of natural materials that are designed to break down and disappear - often within minutes of being finished - you would be forgiven for thinking that he should be languishing in obscurity.

However, this is the age of mass media and an ephemeral design made of dandelions and bracken roots on a windswept hillside in the North of England, can live on in living rooms and gallery walls as a photograph for generations after the original artwork has been carried away by the elements.

As Thomas Riedelsheimer's reverent and beautifully shot documentary reveals, Goldsworthy conscientiously photographs and carefully archives all his creations. It would be a great shame if he did not.

Just as the photographing is a part of the creative process, so too this documentary seems essentially a colloborative process between artist and filmmaker. Goldsworthy would argue we are still taking snapshots, but a motion picture certainly helps one understand his obsession with "growth, time, change and the idea of flow in nature".

Riedelsheimer's camera captures the elegant motion of a leaf-chain snaking downriver and the passing of the seasons around Goldsworthy's stone cones.

Watching Goldsworthy painstakingly shaping ice with his bare hands on a frosty beach, before it thaws in the dawn sun, or striving to balance a collapsing web of twigs - too delicate to withstand the wind - adds to one's sense of appreciation.

At the same time, Goldsworthy appears intense, laconic ("Words do their job, but what I'm doing here says a lot more!") and concentrated, even in the few scenes with his family. He is a man of the land: "I need the land... I need it," he says.

There is no time for anyone to ask how much we need his art, of course, as we follow him on commissions in France, Britain and North America. But then this is not an art lesson, but an appreciation.

Or perhaps not. Goldsworthy talks about "shaking hands with the land", the rocks "talking to him" and "an absence in the landscape". To many his words will make perfect sense. Others may think him half-deranged.

At one point, Goldsworthy is filmed lying perfectly still face-up on the road being rained on. He is getting very wet and looks like he has totally flipped. Then he gets up to reveal a grey body shape framed by the water-blackened tarmac, already beginning to fade to dark in the rain. It is a resonant image.

It is this capacity to surprise with simple, evocative ideas that will make Goldsworthy endure. Even for ninety minutes.