Vanessa Baird reviews a gripping new documentary from Peru which has global implications.

In 2007 Peru's President, Alan Garcia, declared his country open to foreign corporations for extraction of its natural resources – mineral, gas, oil, timber.

And within the first few minutes of When Two Worlds Collide, a tense documentary directed by Heidi Brandenburg and Mathew Orzel, we see Garcia courting US capital and signing a free trade agreement with President Bush.

What Garcia did not reckon on, however, was the clarity and strength of the resistance that would come from the indigenous communities of the Peruvian Amazon. The people who, as this film shows, are so often dismissed by the metropolitan elite as 'primitive', 'savage' or in Garcia's words 'obstacles to progress’; and 'dogs in the manger'.

These people soon cottoned on to the fact that the new laws passed by the Garcia administration to make their ancestral lands 'open to business', without consulting them, were unconstitutional and contrary to international accords (ILO 169, chiefly.)

Their appointed leader, the quietly charismatic Alberto Pizango, set about trying to get an intransigent government to repeal the laws. To no avail. There were mass mobilizations of indigenous people and road blocks that threatened the national economy. In Congress, parliamentarians who were about to debate repealing the contentious new laws, were suddenly stopped from debating them.

And on 5 June 2009, the war of words descended into violence. Police, trying to clear a roadblock near the Amazonian town of Bagua, opened fire on protesters who retaliated with spears.

The following morning, government forces launched a full scale attack on indigenous protesters, moving into the town itself. (We now know, thanks to WikiLeaks, that the Peruvian government was being pressured by the US to use force against the protesters). This film captures the attack in all its shocking ferocity, taking us right to the frontline of the action.

Word spread that a genocide was taking place and so elsewhere a group of indigenous activists seized 38 police at a Petro Peru installation and threatened to kill them. As one TV journalist had predicted, the government's approach to the crisis had all the wisdom of 'dropping a match on gasoline'.

An understanding between indigenous protesters and police that they wouldn't attack each other – 'brother police, our fight is not with you but with the government', was one indigenous chant – fell by the wayside.

During two days of violence, 23 police officers and 10 civilians lost their lives and hundreds were injured. Those are the official figures. The story of the massacre at Bagua has been told before, including in this magazine by our regular contributor in Peru, Stephanie Boyd.

But what makes this documentary exceptional is the proximity to Pizango that the filmmakers enjoyed over a period of several years. We see him at every stage, in his rainforest community, bathing, chatting intimately with his father, addressing a meeting; in Lima, lobbying politicians, escaping arrest by climbing out of the window; in exile in Nicaragua, then returning to face the music in 2010; and finally giving evidence in the first phase of the trials against the Bagua protesters in 2013.

By then the hated laws had been repealed in a government climbdown and Garcia was no longer in power. But deals are still made with foreign corporations 'under the table' and without consulting the indigenous inhabitants of the land. Over 50 protesters remain charged with crimes associated with the Bagua events; Pizango and three other indigenous leaders are accused of inciting murder, kidnapping and conspiracy against the state – charges they deny. No government official has been brought to justice to date over the affair.

Pizango speaks simply but with a depth of environmental wisdom. Don't destroy nature for short-term gain, he says. If we contaminate it and it will die and so will we. Film footage of rivers turned into hellish ponds of crude oil and forests stripped bare by logging, show us what he is talking about. 'We only borrow the land, we do not own it. It is our duty to look after it so that we hand to future generation in a good a state or better than we found it,' he says.

We see the indigenous leader making mistakes (declaring the protest an 'insurgency' in a country that suffered decades of appalling violence on account of a Shining Path 'insurgency' was not a wise move). His early reluctance to express regret at the police deaths as well as the indigenous victims was unhelpful.

For dramatic impact, the film presents the central conflict very much as a story of two powerful leaders, Garcia and Pizango, pitted against each, with two contradicting world-views. But the reality that emerges, through interviews and a wealth of painstakingly edited archive material, is far more complex than that.

For a start, there are all the people in between, who are neither indigenous Amazonians nor members of the neo-liberal elite. Take Flor Montenegro, the impressive widow of a police commander who lost his life in the violence. Through tears of grief at his funeral she is able to extend a hand of peace to her 'indigenous brothers'. Or Felipe Bazan, who, in his quest to find his missing police-officer son, finally asks Pizango for help. Even after he has discovered the worst, the father's verdict is: 'Ordinary people died because of the government's greed'. What is it, he says 'when oil or a piece of gold is more than life?'

It would have been good if we could have heard more from the families of indigenous victims of the Bagua massacre and the impact the tragedy had on them. Also, there should have been mention of reports that scores of indigenous protesters are missing and the death toll is probably much higher than official figures suggest.

But, quibbles aside, this feature-length doc is a tremendous achievement, especially bearing in mind it's a debut for Brandenburg and Orzel. It deals with an extremely complex national reality, providing a narrative that is both in-depth and dramatic. The photography is stunning, and the editing tight enough to keep the narrative moving at a cracking pace. The issues raised are key to both democracy and environmental survival. It's a story that is about specific events in Peru but which also has global resonance; it's relevant to all who share, and will share, this planet.

Star rating ****

When Two Worlds Collide is currently on release in Britain.

To read more about the indigenous resistance to corporate greed in Peru see our award winning magazine Nature's Defenders.