A case study of environmental degradation in Austin, Texas over the decades is skillfully employed as an example of the pervasive tension between development and preservation in Laura Dunn’s “The Unforeseen,” a thought-provoking documentary that’s both informative and strangely poignant—as well as beautifully shot and edited.

Interestingly enough, the main actors profiled in the decades-long quarrel over the preservation of the Barton Springs recreational area and the Edwards Aquifer to which it’s connected aren’t the community activists who fought to protect them—though they’re certainly present and archival footage of their testimony before city council meetings is powerful and persuasive. (Robert Redford, one of the film’s executive producers, is also interviewed about learning to swim in the Springs and how it can be seen as an example of communal meeting places that are being degraded everywhere. And political figures who helped the organizers temporarily halt development—like Governor Ann Richards—also have their say.)

But they’re overshadowed by Gary Bradley, a lead developer in the scheme, who’s profiled as the ambitious son of farmer who left the family homestead to make his way in the capital and began an influential players in the city during the explosive growth of the1980s. There are extensive interviews with him as he describes his initial successes and his ultimate decline and fall in the face of public opposition. And his final remarks—more regretful about his financial losses than any environmental concerns—skillfully juxtapose his personal problems against the public consequences of his land deals without making him a one-note villain.

Equally subtle, though less considerate, treatment is accorded to lobbyist Dick Brown, whom cinematographer Lee Daniel photographs without ever showing his face as he meticulously constructs the model of a military aircraft. Daniel describes how he marshaled opposition in the state legislature against local action to halt already-planned development, helped form citizen pro-development groups, and eventually secured a reversal of Richard’s policies by the newly-elected George Bush. Other voices are heard on the development side as well, including those anxious to sell their property at the highest possible price.

And standing between the two sides is the figure of a hardscrabble farmer whose small, run-down holding is being encroached upon by endless rows of track houses and who, like a stand-in for Bradley’s father, poignantly observes how the land is changing and people like him are becoming scarcer and scarcer. (Comments from new residents about the emptiness around their houses and the water restrictions immediately placed on them add to the effect.)

But though the pro-environmental message of “The Unforeseen” is unambiguous—the contrasting shots of the clear aquifer waters from decades past and the murky ones of today are sufficient evidence of that, and the political machinations behind policy changes are hardly portrayed in flattering terms—the tone is regretful rather than rancorous, and while change isn’t celebrated, neither is it summarily condemned.

The excellence of the picture is enhanced by its broad visual palette, which uses the customary one-on-one interviews and news footage but imaginatively employs maps, underwater shots, manipulated helicopter footage and others graphics in a hypnotic collage. The images are complemented by an equally eclectic mixture of background music, and by periodic recitations by poet Wendell Berry.

“The Unforeseen” will probably be seen for the most part by people who already agree with its point of view. But as “An Inconvenient Truth” demonstrated, one can never tell when an exceptionally well-made documentary might have a broader impact than you might expect.