The old adage "a picture is worth a thousand words" needs to be rethought. More importantly, a picture can have the power to move a thousand hearts and change a thousand minds. Often, photographs bring to our eyes what we may have seen many times before, but not noticed. They can shed new light on the everyday and the ordinary. They can redirect the course of our vision, so that we see, think, imagine and even, perhaps, act differently.

No doubt, one of the most pressing campaigns of our times is that for sustainability and environmental awareness. In the ruthless course of modernity, our approach to nature has been one of extraction and use. We urgently need to alter how we relate to the world around us and to re-educate ourselves in terms of the larger planetary scheme, hung, as it is, on a delicate ecological balance that is being dangerously disturbed by our many modern machinations in the name of science, technology, development and progress – and, dare I say it, capital.

Nature photography has become a potent tool in this struggle. Through it, we learn of the many others – the wondrous diversity of flora and fauna – with whom we cohabit on this planet. It is also, as the Guardian's nature photography project reveals, a medium taken up by professionals and amateurs alike. So, what role does photography play in defining our relationship with nature? What do images of nature and wildlife tell us and why do we feel compelled to view them? Who among us has never been moved to snap a sunset on the horizon, a flowing river, a blossom in spring?

Our zeal for visually representing nature has a long and complex history. The advent of photography was celebrated as a milestone in the modernist quest to capture nature better. For early photography was largely devoted to documentary purposes and, in the apparent fidelity of its representations, the camera in the 19th century exceeded the naturalist drives of painters who, during the Renaissance and early modern period, tried to explore, and so tame, nature by rendering it into art.

Photography, however, is poised on a fine borderline between documentary and art. Never just one or the other, photographs can exceed the set frame. Moreover, the photographic frame can reveal the unsettling ability to extend and include us in its space. Photography is inclusive in its mediatory role. It extends covenants.

Often, nature photography calls on modern humanity's sense of nostalgia for a harmony between man and the environment. As John Berger has rightly stated, the way we see is conditioned by our history, and so it is that we may look at nature in terms of loss. As with the many images of the recent oil spill off the coast of Florida, this can be founded in fact and so provoke a sense of culpability, a sudden awareness or questioning of our precepts and actions. Photographs lead us to rethink, to realign the frame of our understanding.

The force of photography also lies in its playfulness. And by this, I mean the many overlapping discoveries of unvoiced knowledge, feelings and imagination that we stumble upon via images. So, the flipside of loss or pathos can be a freshness of vision or a change of perspective. Above all, nature photography lends to our lives what we long ago lost in our modern abandonment of nature – the experience of wonderment, that sense of discovery, newness and awe.

Take, for example, Ernst Haas's images of dramatic skies, the elements and the seasons. His work, dramatic and inspiring, calls upon our pre-modern imaginations of the world at its most elemental, charged with a dynamic energy.

Photographs can also point out the extraordinary or magical in the seemingly irrelevant, as in Bolucevschi Vitali's prizewinning image of ants poised like dancers in stellar form. Modernised, urbanised and alienated as many of us are, photographs remind us of nature's many complexities and subtleties. Or, as in Sebastião Salgado's on-going project Genesis that is linked to an equally challenging project at the Instituto Terra to restore Brazil's Atlantic rain forest, photography marries wonderment, amazement and joy to a well-defined and articulated commitment to the planet. It melds fractures and helps envisage solidarity in our imbalanced and fractured world.

So what moves us to snap a sunset on the horizon, a flowing river, a blossom in spring? The photograph by itself is only a token of a moment gone by. Its power lies in the metaphor, for photography captures our minds more than we capture the subject.

In the case of nature photography, we discover that the battle for sustainability and environmental balance is not something fought "out there", in the distance, but one that ultimately returns us to the natural. Environmental photography matters, because it offers the lifeline of a bridge between our modern, denaturalised, mechanistic mores and the imperative of nature within and without.

Previously published in The Guardian