Art critic and activist Lucy Lippard thinks of photos as the imperfect means we moderns employ to fill gaps in our society's memory. According to her, images can "survive" while we continue to lose the places we try to capture on glossy paper. Flipping again through the color plates of Elliot Porter's ode to Glen Canyon, The Place No One Knew, I cannot help but feel a mix of despair and nostalgia. Too young to have seen this gem of the Colorado Plateau myself, I almost wish his photos were not there to remind us of the fortune we squandered. Scores of calendars and pictorials celebrating red sandstone landscapes - a friend calls them "nature porn" - may lull many into believing all is well in the Four Corners.

Photography's claim to objectively depict reality is as old as the medium itself. Almost from its beginnings, though, another motif has complemented pure documentation: the undercurrent of artistic vision. The focused gaze strives not only for representation, but also for an essence closer to truth than anything we could hope to behold with the naked eye.

Landscape photography in particular aimed - until recently - mostly at revealing what is divine in the material world, emphasizing the extraordinary over the quotidian. Pictures of waterfalls and bizarre rock formations, of sublime light bouncing off slot canyon walls, cloud-lined vistas and portraits of rare desert creatures can all be ascribed to this category. "Scenery" and "scene" (a theater term) share the same root. In our troubled times, many a landscape photographer stages images at the shrine of harmony, worshipping an age-old ideal. Beautification, and postcard romanticism are the goals, which handsomely translate into dollars. Choice of subject matter and context (or lack thereof), focus, perspective, and final editing all take advantage of visual ruts, the pre-dispositions of nature lovers looking for (and at) promises of a whole and wholesome world. But like any art form, the genre does not exist in a value-free vacuum; it finds deeper meaning only against a specific cultural background. Anthropologists who trained Navajo students in the use of cameras to document their desert home were surprised by the results. The footage and stills their pupils brought back not only questioned western "narrative" conventions; they also contained many shots of family members, buildings, and domestic animals, which, for the Navajo, constitute an essential part of the land. Our own sensibility largely insists on a strict separation of Nature from Culture. We prefer our landscapes untainted, untrammeled, without signs of human intrusion. Even lay photographers try hard to keep power lines or dirt roads out of their frames. (The products are not to be confused with the "been-there-done-that" snapshot.) This perspective is "art-ificial," "artifice" in the truest sense of the word. We should remember that concepts like "wilderness" are as meaningless to a Navajo or Eskimo as our distinction between people and their surroundings.

Ever since Henry David Thoreau penned his provocative essays, "nature writers" have found themselves at the interface between art and activism; now, increasingly, "nature photographers" as well are forced to take an unequivocal stand. Like a two-edged blade, the camera can serve advertising and industrial tourism, or else question the exploitation and commercialization of threatened places and ways of life. There are precedents for the latter use; photography has supported campaigns for southwestern landscapes: from Ansel Adams' glorification of Yosemite Valley as a national treasure worth protecting, to Porter's book, which the Sierra Club used to fight Glen Canyon Dam. These attempts still appealed mostly to our sense of beauty, to our hearts rather than intellects. But unfortunately, sentimentalism or aesthetics alone cannot win conservation battles. While very few "coffee table" books illustrate environmental atrocities or conflict and thus threaten to alienate readers, there is a sensible and effective middle ground. Collections of repeat photography (like White and Engler's The Lens of Time or, closer to home, Robert Webb's Grand Canyon: A Century of Change) choose to replicate historical landscape shots from the same camera position to show subtle (or not so subtle) alterations of landscapes over time. These may be human-induced or natural, like erosion. It seems that photography - and specifically landscape photography - has returned to its origins as a means of documentation.

And yet. A few weeks ago I was lingering over a pair of repeat shots that show a slickrock scene somewhere in canyon country. Except for the quality of photographic lenses and stock, not much had changed in more than 50 years. My eyes snagged on a juniper tree hunched in the foreground. It looked . . . so fragile. Barely hanging on in a parched land, it had remained virtually unchanged. It inspired awe. It encouraged me to help it survive its own images.

Michael Engelhard is the author of Where the Rain Children Sleep, as well as the editor of two anthologies.