MOVIES / COMMENTARY : When Worlds Collide : ‘Black Harvest’ is gripping, flabbergasting and indelibly entertaining. Did we mention it’s a documentary?

An exceptional motion picture, recent winner of a worldwide 380-film competition and the capstone of a trilogy that has dazzled critics and won dozens of international awards, is opening theatrically today in Los Angeles.

Two years late.

For an abbreviated run.

Showing at 11 a.m. only.

The key to this seeming riddle is that “Black Harvest,” screening today and next Saturday and Sunday at the Nuart on Santa Monica Boulevard in West Los Angeles, is a card-carrying member of that most shunned of all genres: the documentary.

Nothing, unfortunately, shouts “unclean” at today’s theatrical audiences so much as that category, with the result that “Black Harvest” is being shown as part of a series carefully labeled “Nonfiction Film” to avoid contamination by that accursed 11-letter word.

This is especially true in nominally sophisticated Los Angeles, where, exceptions like the long-running “Visions of Light” notwithstanding, movie-goers seem to view documentaries with the kind of antipathy usually associated with freeway diamond lanes. But if it took an earthquake to make those lanes palatable, maybe this aesthetic quake will do the same for the documentary genre.

For the overwhelming irony here is that “Black Harvest” (which may get an expanded run if the box office warrants it) is more gripping, flabbergasting and purely entertaining than 90% of what usually appears on movie screens. The unexpected resonances of its story, the vividness of its cast of characters, and the passion with which it’s been made all translate into an indelible movie experience.

Bob Connolly and Robin Anderson, the Australian filmmaking team (he does camera, she sound and they both edit with Ray Thomas) spent more than a dozen years making the trilogy that “Black Harvest” concludes. Though this final film contains a recap of the first two (“First Contact” and “Joe Leahy’s Neighbors”) and stands completely on its own, a bit of background information is helpful.

All three films are set in Papua New Guinea, the large island nation just north of its former colonial master, Australia. One of the last places on Earth to be affected by Europeans, Papua New Guinea was largely untouched until 1926, when the discovery of gold brought the inevitable invasion of outsiders. Still, because the interior of the island looked to be one continuous and impenetrable mountain range, no one thought to search inland. Until the Leahys.

Lead by Michael, the eldest, and joined at varying times by brothers Patrick, James and Daniel, the Leahy mining expeditions were in many respects typical of prospectors looking for the big strike. But as they ventured inland, a pair of related developments confounded everyone. Those supposedly impenetrable mountains turned out to contain huge and fertile hidden valleys, valleys inhabited by close to a million people who had never seen, heard or so much as imagined the existence of white people.

Encounters like this had been taking place for hundreds of years, ever since Columbus, Cortes and Pizarro came to what they called the New World. What made the situation in Papua New Guinea different was a simple quirk of fate. Michael Leahy was a photography buff, and along with his mining gear he had casually brought along both movie and Leica cameras.

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The extraordinary result (related in “First Contact”) are several hours of 16-millimeter film and 5,000 still photos that for the first time documented the way indigenous peoples reacted to the incomprehensible appearance of pale-skinned invaders. The looks of awe and terror Leahy’s cameras recorded let us see just what Columbus and all the rest must have seen on their arrival in an unprepared world.

The tribal men thought that these pale people were spirits or gods, but the women found out soon enough how human they were and several mixed-race children, never recognized by their fathers or fully accepted by the tribes, were born.

Of these, Joe Leahy, Michael’s unacknowledged son and the protagonist of “Joe Leahy’s Neighbors” (like “First Contact” available on video from Documentary Educational Resources in Watertown, Mass.), was easily the most prominent.

Made in the mid-1980s when Joe was in his 40s, “Neighbors” details his interaction with the Ganiga, a prominent highland tribe. More educated and entrepreneurial than the Ganiga, who still live quasi-traditional lives, Joe buys land from them and turns it into a successful coffee plantation, which in turns leads to tribal resentment about Joe’s determination to keep all his profits for himself.

“Black Harvest” opens with Joe at the peak of his influence. That first plantation has made him a wealthy man and, partially to quiet that resentment, he has gone into partnership with another of the Ganiga clans, lead by Popina Mai, a charismatic “big man” with the face and manner of an Old Testament prophet.

Joe, who promises the tribe that “you’ll be up to your necks in money,” provides the expertise, the tribe the land, with profits to be split 60-40. Five years after the deal, with the new plantation preparing for its first harvest, the filmmakers returned to see what would transpire.

Connolly and Anderson’s commitment to stay in the highlands for as long as it took for the story to unfold--even though it meant living for a year with their infant daughter in a grass hut they built themselves--is one of the keys to “Black Harvest’s” success. For what did unfold was a tale no one could have anticipated, a wrenching, human story that reverberates with personal and global implications while revealing a singular culture from the inside.

It is a culture, first of all, that greatly admires oratory, and one of the film’s unexpected pleasures is to hear premier public speakers like the expressive Popina Mai powerfully declaim in Temboka, the melodic local language, about the burning issues of the day. Of which there turn out to be several.

First of all, no sooner is the new plantation ready to harvest than worldwide coffee prices drop steeply, and not only won’t the Ganiga be up to their necks in money, they’ll be forced to do the bean picking for less wages than they have in the past in order to keep the plantation out of the hands of the bank.

And if this crisis wasn’t enough, the Ganiga get halfheartedly drawn into a tribal war that is not really their affair. But like all wars, this soon escalates out of everyone’s control, keeping Joe’s workers away from the plantation and wreaking havoc with all of his and an increasingly haunted Popina Mai’s careful plans.

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From a visual point of view, the footage Connolly and Anderson got of these bow-and-arrow tribal battles, during which one of their closest friends, a key player in “Joe Leahy’s Neighbors,” was killed and their own hut burned, is riveting, a startling glimpse into prehistory.

Ironically enough, that footage may have kept “Black Harvest” from being nominated for a best documentary Oscar last year, when persistent rumors had it that a minority of the nominating committee felt these shots had been staged. In a public letter issued in response to the controversy, Connolly and Anderson underlined the methodology that make their films so effective: “To not interfere, manipulate, stage, interrupt, but to unobtrusively observe is absolutely central to our filmmaking philosophy.”

And though the war footage is visually arresting, it is in fact a sidelight to why this film is such a knockout. For what “Black Harvest” focuses on is Joe and Popina Mai trying to cope with these crises. It is concerned with what happens when the 20th Century meets traditional ways, about a people forced to confront the shaky coexistence between revered tribal customs and lust for what Western modernism can provide.

But potent as it is on that level, “Black Harvest” is even more effective when it personalizes these dilemmas. For at base this is a story about the death of dreams and all the anger, exasperation and sadness that goes along with that. It is a story of two men caught between competing cultures who both have reason to feel angry, trapped and betrayed, victims of societal forces that are well beyond anyone’s control.

And though Joe Leahy tells Popina Mai at one point, “Nobody cares about us and our little enterprise, we’re insignificant,” “Black Harvest” shows that that doesn’t have to be true. As told in this singular film, their story becomes not only our story, but in some ways the key story of the past 500 years.

* “Black Harvest,” screens today , Saturday and next Sunday at the Nuart on Santa Monica Boulevard in West Los Angeles.