Amazon Letter: This city of nearly two million people in the heart of the Amazon rain forest ranks among the strangest urban centres on the planet.
One thousand miles up the mighty Amazon river from Brazil's Atlantic coast, it has no roads in or out, yet factories in the city's special duty-free area produce hundreds of thousands of motorbikes for export each year.
An elaborate cream and pink opera house in the city centre, its interior fittings shipped from far away Portugal in the mid-19th century, bears testimony to an exotic past when Manaus was the centre of a rubber boom - a period which abruptly ended when the British stole the seeds, cultivated them at Kew and shipped them out for planting in Ceylon and Malaya.
Temperatures rarely drop below 30 degrees - and in the hottest months early in the year the barometer often goes over the mid-40s. The weather is a subject of constant debate.
"There's no doubt it is getting hotter and hotter," says Dr Carlos Rittl, a Brazilian ecologist living in Manaus. "The continuing deforestation of the Amazon, together with the wider impact of climate change, is severely affecting the whole situation in the Amazon basin."
The world's rainforests, of which the Amazon is a major part, are often referred to as the lungs of the planet. Scientists say any disruption to the climate in this region can have far-reaching consequences for the earth's weather systems. Dr Rittl says there is growing evidence that the increasing force of hurricanes in the Gulf of Mexico are linked to recent severe droughts in the Amazon.
"The warming of waters in the west Atlantic has the effect of sucking the humidity out of the Amazon. More than 50 per cent of the rainfall in the Amazon is actually generated within the rainforest itself. If the humidity isn't there, then rainfall drops and there's a drought. It happened last year and all the signs point to it happening again this year.
"That creates a terrible cycle - the drier the land, the more fires spread and the more forest is destroyed. It could be devastating - not only for the Amazon and Brazil, but the whole world."
Last year's drought, centred on the southwestern province of Acre close to Brazil's border with Peru and Bolivia, was unprecedented. The drying out of this normally wet region caused forest fires over a large area - an estimated 250,000 hectares were burned.
"What we call the dance of the winds round the earth is not happening in the normal way," says Actino Machado, an Acre resident. "There have been 30 days without rain in the last month. It shouldn't be happening and the fires have already started. The whole thing is an ecological time bomb."
Climate change and drought are not the only problems facing the Amazon. The government of President Lula da Silva, facing elections later this year, has pledged to curtail deforestation, yet an area larger than the size of Wales was slashed and burned last year alone.
Multi-millionaire cattle ranchers moving into pristine rainforest areas have traditionally been blamed for setting fire to the forest and evicting indigenous people from their lands.
The new enemy of the Amazon is the soy bean. Brazil is now the world's leading soy bean exporter - last year alone, more than 50 million tonnes of soy was produced on lands stretching across nearly 23 million hectares, an area approximately the size of Britain. While these exports have contributed to a spurt in Brazil's economy, the country's "soy barons" have destroyed enormous tracts of rainforest. Until recently, soy was grown mainly in Brazil's southern states, but now the monoculture is encroaching on to lands further north.
Ironically, this is in part due to Europe's insistence on non-genetically modified (GM) foods. GM crops are mainly grown in the south - now, to cater to the needs of Europe, soy farmers are planting large tracts of land with non-GM soy in the Amazon, clearing the forest along the way.
The American food giant Cargill has built a new loading facility at Santarem, halfway between the Atlantic coast and Manaus. Locals say the construction happened without proper permission. All the exports are destined for Europe, going through the ports of Liverpool and Rotterdam.
"The soy going to feed cattle, pigs and poultry, for food for the people of Europe, is grown on lands cleared from the Amazon rainforest," says Edilberto Sena, a priest who runs a radio station called Radio Rural in Santarem. "People in Europe should be aware of what's happening. The rich and powerful are destroying the land and robbing people of their homes. There is growing unrest and violence."
Assassinations and violence have become part of life in the Amazon region as local people confront the soy growers and processors.
In the most famous recent case, an American nun, Dorothy Stang, who campaigned on behalf of local peoples rights, was assassinated east of Santarem last year by a gang trying to evict people from their lands.
"I have received death threats," says Fr Edilberto Sena. "We are little people fighting giants. The outside world must help us - not only in the fight for justice but also to preserve the forest, for Brazilians and for the good of the whole world."