 In the forest, there are no horizons and so the dawn does not break but is instead born in the trees - a wan and smoky blue. I twist in my hammock. The total darkness, which has been broken only by the crazy dance of the fireflies, is fading and now shapes are forming - branches, fronds, vines, bushes, leaves, thorns, the soaring reach of the canopy, the matted tangle of the understorey. The crazed clamour of the night - growls, hoots, croaks - has died away and for a moment there is almost hush. This is also the only time of cool and I can see thin fingers of mist curling through the trunks and drifting across the river beyond. a butterfly passes in the quavering grace of its flight. Then, suddenly, the great awakening begins and the air is filled with a thousand different songs, chirps, squawks and screeches - back and forth, far and near, all around. So loud and so raucous and so declarative of life is this chorus that nothing anywhere in the world can prepare you for it.  I am camped deep in the Brazilian amazon with my guide.  Like most people, the first time I arrived in the amazon, in 2003, I knew almost nothing about it. I had only a vague first-world notion of "deforestation" and this being bad. I did not know why, specifically, it was bad, or for whom, or how, or in what way any of this actually mattered. But in a place called Puerto Maldonado, a forest-frontier town in south-eastern Peru, a woman told me a story about a scientist who disappeared in terrifying circumstances. and I knew that I was at the beginning of a long process of self-education.  In the past few months, the amazon has made a return to the news for several reasons. In February, startling aerial footage of uncontacted tribes on the Brazil-Peruvian border, brought to us via the great Brazilian anthropologist, Jose Carlos dos Reis Meirelles, was released (you may have seen the footage on the BBC's Human Planet). a subsequent letter from the Peruvian government "recognised the situation of the peoples living in isolation and/or initial contact" and promised, for the first time, that five new reserves for indigenous communities were "in the pipeline". We shall see. . .  In March, three tribal leaders arrived in London to make their case against several huge hydroelectric dams being built in Brazil and Peru, which they argue will force their people from the land and threaten their way of life. and within the past few weeks, Peruvian security forces have launched an unprecedented operation to destroy the unlawful gold-mining dredgers that are now killing off river habitats by pumping up river-silt.  Part of the reason we struggle to understand the region is that there is so much to take in. and because there has been some (partial) good news on the headline problem - deforestation - it has faded in our collective consciousness in the past few years. So it's worth stepping back and reminding ourselves of some of the fundamentals.  The area of the amazon rainforest - roughly 2.3m square miles - is larger than Western Europe and the forest stretches over nine countries: Brazil, Peru, Colombia, Bolivia, Ecuador, French Guyana, Guyana, Surinam and Venezuela. There are approximately 1,250 tributaries that service the main river, 17 of which are more than 1,000 miles long. The river is bigger in volume than its six nearest rivals combined and discharges into the ocean about 20% of the total freshwater of all the rivers in the world. Roughly a fifth of the earth's oxygen is produced in the amazon rainforest ("one breath in five" as a guide once put it to me) and more than two-fifths of all the species in the world live there. You can find over 200 species of tree in a single hectare of amazon rainforest and one tree can be home to 72 different species of ants alone. Over its 4,000-mile length, no human bridge crosses the amazon river.  IGNORaNT aS I WaS, the most surprising discovery when I first visited was that oil is one of the main resurgent threats to the region. Since my first visit to Peru in 2003, the amount of land that has been covered by oil and gas concessions has increased fivefold - almost 50% of the entire Peruvian-owned amazon. This means that the government has effectively sold off half of the rainforest it owns for the specific purpose of oil and gas extraction in return for taxes, bonuses, royalties - 75% is forecast by 2020.  Every time there is oil exploration, there is major disruption and destruction to the forest, starting with seismic testing and following through with helicopters, roads, oil wells, crews and so on; each development brings a chaos of unplanned settlement and more deforestation. and inevitably, whenever oil is found there are catastrophic spills and accidents. a lawsuit is being brought to court by members of the indigenous achuar tribe for contaminating the region. Health studies have found that 98% of their children have high levels of cadmium in their blood, and two-thirds suffer from lead poisoning.  There are hundreds of Indian groups from one end of the forest to the other - many of them now enmeshed in legal cases or "integration projects" or other demoralising fiascos - but those that most often capture international attention (ironically) are the uncontacted. There's some dispute as to what exactly is meant by the term. Beatriz Huertas Castillo works out of Lima and (along with Jose Carlos dos Reis Meirelles in Brazil) is one of the  people who knows most about the subject, having spent much of her life travelling in, researching, documenting and writing about the very remote areas these peoples inhabit.  "The uncontacted are indigenous peoples," she explains, "who, either by choice or by chance, sometimes as a result of previous traumatic experiences, sometimes not, live in remote isolation from their national societies. There are at least 14 such tribes in Peru. We think 69 in Brazil. Maybe 100 in the amazon area as a whole."  The best way to think about the remaining tribes in 2011 is to imagine a series of concentric circles, all of which interact on each boundary. There are the tribes that stay on their own homelands in the forest (or seek to do so), but who have regular relations with the outside. These retain a strong tribal identity, but they are coming to know the world all too well; they will travel to fight legal battles for their territories and their children will leave for the cities. Then there are a good number of tribes (or parts of tribes) who have been contacted, but who have very circumscribed dealings with the outside world; while no longer in isolation, these live (or try to live) as they always lived. Then, in the heart of the forest, there are these few remaining uncontacted peoples. They may have heard rumours from their grandparents, but they are among the handful of peoples left alive on the planet who have next to no idea of what the world has become. They live as they have done for thousands of years - before the internet, the world wars, the United States, the Tudors, Christ, aristotle or abraham.  "I spoke to Mashco-Piro women when they were first contacted," says Castillo. "and they were terrified of disease, of being slaughtered, of their children being taken into slavery. In the past, every encounter has bought terror for them - they have no immunity to our diseases and they were thought of as animals, even hunted. and now they see the loggers and the oil companies coming in a little further every year. and for them it's the same thing so they flee into neighbouring territories."  Then there's the ongoing damage caused by illegal logging, not to mention the cocaine problem. Besides the loss of the trees themselves, it is the incursions and what follows that have the most impact. (although it's important to note that there has been a victory of sorts in Brazil - the mahogany trade, in particular, has been tackled.) It is estimated by the UN that coca plantations in the area of the Peruvian amazon increased by roughly 25% between 2003 and 2008. Leaving aside all the other issues that swirl around narcotics, the way the cocaine base is prepared leads to the dumping in the water of millions of gallons of kerosene, sulphuric acid, acetone, solvent, and tonnes of lime and carbide. The extraction of gold is equally toxic because of the use of mercury.  But it's what the explorer, writer and amazon expert John Hemming calls "the bloody mess of the dams" that is causing the latest round of acrimony, fear and dispute. a series of new hydroelectric dams (more than 100 in total) are planned across Brazil and Peru, including the most controversial of all - the Belo Monte Project on the Xingu river, which is intended to be the world's third largest hydroelectric plant. It was to raise awareness of these that the indigenous leaders toured Europe last month. These really caught me out. Surely a good idea, I thought, but, sadly, it's not so straightforward. . .  The problems, as Hemming explained, are these: first, they will flood the territories of the tribes; the dams release vast amounts of the greenhouse gas methane, due to rotting vegetation; they release all the carbon in the forest that is destroyed to make way for them; they bring further roads and colonisation in their wake; they change the flow and run of all the river systems, which affects untold numbers of aquatic species, not least the fish that so many people in the amazon eat, meaning that they will have to import more food, meaning more roads, more beef, and so grimly on.  It is important to acknowledge that not everything is getting worse. Some of the campaigning in the past 20 years has worked and there are cautious grounds for hope and good reasons to continue. When, in 2006, I was in Manaus, the great river city right in the heart of the amazon, I heard contradictory accounts of progress and regression. Paulo adario is a veteran ecologist who lives there. He is probably one of the individuals to have done most in the service of conservation alive today, and he is happy to bring me up to date.  "Since the 2004 peak of 27,000 sq km of forest destroyed, matters have improved with regard to deforestation," he says, when I call him. "Last year we lost 6,500 sq km. You can say productivity is better with cattle and with soya. We're seeing more yields in existing areas that have already been cut. You can also say that the Brazilian government's approach to the uncontacted people is very enlightened. and that - yes - the satellites have helped combat illegal logging: there have been arrests and maybe we are winning the mahogany battle."  The 6,500 sq km lost last year is still an area more than four times the size of Greater London. adario is also very worried about imminent changes in the laws in Brazil, which will once again relax the strictures against forest development. "They are going to send out a big message that if a law does not work for you, then don't feel you have to respect it. Only an idiot would follow the rules in the  forest if all his competitors were making fortunes by ignoring them."  TIME ON THE RIVER is like time at sea. It's not measured in minutes, but in the way the light changes the colour of the water. at dawn, there are mists and the river appears almost milky. By noon it is the colour of cinnamon. and then, in the evening, when the trees seem almost sinister in the intensity of their stillness, the low sun shoots streaks of ambers and gold from bank to bank before the dusk rises up from the forest floor and the shadows begin to stretch and everything turns to indigo.  One such evening, we went to visit a fisherman whose grandfather had been among the first of his tribe to be contacted. His own sons were wearing football shirts and his eldest was training to be a guide. Using his son as an interpreter, he put it like this: that the amazon matters because right now it is where humanity - you, me - is ma 