One of the most underrated films of last year was The Constant Gardener, a film based on John Le Carré’s novel about the exploitation of the African continent in the service of Western pharmaceutical profits. That story was Graham Greene-like in its journalistic authenticity, political sophistication and moral self-examination. Now there’s an actual documentary that outlines another kind of Western profiteering in that continent. Darwin’s Nightmare, a film by Hubert Sauper, was nominated for an Oscar this year, losing to a different Darwinian drama called March of the Penguins.

In truth, the film’s title is more of an attention-grabber than an accurate representation of a film that should be considered the human race’s nightmare. Sauper’s film is a punishing account of global free trade as a zero sum game. Everything the affluent West takes from Africa makes it richer, and all of Africa’s recompense comes in the inverted form of suffering at the hands of war, famine and pestilence.

Sauper begins his film almost as if it really were a novel by Greene or Le Carré, with a long shot of a plane on a glide path over Lake Victoria, the world’s largest tropical lake and source for Europe’s abundant supply of Nile perch. The next thing we see, however, is the inside of an air traffic control room (it doesn’t appear to be a tower) in Mwanza, Tanzania. The sole controller on duty, we see, is having difficulty communicating with the planes, partly because of faulty radios but mostly because his workspace is teeming with the sort of insects Hitchcock would have created had he made a film called The Flies.

Having established his hellish setting, the Austrian-born Sauper begins to tell his story, often by conversing with his interview subjects (although we never see him). Mwanza is one of many towns that have sprung up along Lake Victoria to exploit the area’s sole natural resource, the Nile perch. The Nile perch is a huge and hardy fish that sometimes tops 6 feet in length. The fish processors in Mwanza alone export 500 tons of it every day, to a rich and hungry European continent.

There are several things wrong with this picture: For starters, the Nile perch is a non-native, invasive species that, since its introduction a half-century ago, has wiped out virtually all of the indigenous fish, including those that feed on algae and waste. So scarce are other species that the Nile perch now has to cannibalize its own young in order to stay alive.

But that’s not all. Sauper’s obsessive question throughout the film is, what do those huge, 55-ton Ilyushin aircraft bring when they fly down to pick up fish? Surely, in a world run by the supposedly rational rules of trade, those airplanes must be bringing goods of some kind to barter for all that fish. But that doesn’t seem to be the case. Over and over, Sauper asks his subjects about this, but few seem willing to say out loud what seems to be the truth, that these planes are bringing munitions that are contributing to the deadly wars in neighboring Rwanda and Congo.

Darwin’s Nightmare may be the most horrifying film you’ll see this year. While we may understand that there are millions of people in the world who are “less fortunate,” we don’t really understand what that means until Sauper shows us Tanzanians eat the rotting, maggot-infested fish carcasses that remain after the choice fillets have been airlifted north. Sauper shows us how the plastic fish packaging is recycled by desperate orphans who melt it into a sniffable mineral spirit. He shows us prostitutes with bruised and scarred faces, and young children with missing limbs. One initially sympathetic priest describes the shocking death toll from AIDS in his makeshift parish, but after Sauper prods him, he admits that he discourages condom use in his flock. In some wretched parts of the earth, the post-apocalypse is right now.

Sauper put himself in considerable peril to make his film, and he is admirably respectful as he is relentless in his questioning. According to recent reports, a number of participants in his film are being harassed by the Tanzanian government, which blames the film for a sag in European consumption of Nile perch. If there’s any reason to feel hopeful after seeing Darwin’s Nightmare, it’s the sight of a few brave Tanzanians who, against all reasonable odds, are bearing witness to the ongoing depredation of their people by Europeans and Asians, and by their own corrupt government.

But any hope we feel should be short-lived. As in other films that expose the underside of globalization happy-talk, such as Stephanie Black’s Life and Debt, we have to reckon with the leviathan of capitalism. As a supposedly rational system of production and distribution, in which supply and demand come together in happy convergence, capitalism is ruthless in rendering large groups of people expendable. We may need to reexamine the very language of the ideology, bearing in mind that whenever we employ athletic metaphors like “compete” when we talk about the global economy, we are implicitly suggesting that along with winners there must be losers.

Outraged, shocking and sometimes barely watchable, Darwin’s Nightmare nonetheless makes a persuasive case that the Nile perch isn’t the only species that is devouring itself.

Darwin’s Nightmare opens Friday at the Chelsea in Chapel Hill.