The early hours of the morning in the Pantanal can be an almost deafening experience, as this beautiful wetland area wakes up to a symphony of natural sounds.
There are said to be more species of birds here than in the whole of Europe, living among a patchwork of rivers, lakes, lagoons, forests and islands.
The birds are just one part of an abundance of wildlife which makes the Pantanal "a vast ecological sanctuary".
Here you can find everything from the alligator-like caiman to the anaconda, one of the biggest snakes in the world.
There are more species of birds in the Pantanal than in the whole of Europe
The Pantanal is one of the largest continuous wetlands on the planet, spread over 150,000 square kilometres.
The largest part of this flood plain lies in Brazil, divided between the states of Mato Grosso and Mato Grosso do Sul, but it also extends into parts of Bolivia and Paraguay.
Such is the scale of the place that the first European settlers who arrived here thought they had discovered an enormous inland sea.
As well as around 700 species of birds, there are some 50 different types of reptiles and hundreds of species of fish including the piranha.
While no-one disputes the uniqueness of the Pantanal, in recent years concerns have been raised about the impact our changing world is having on this fragile ecosystem.
150,000 square kilometres
Largest part in Brazil, but also extends into Bolivia and Paraguay
700 species of birds
50 different types of reptiles
Hundreds of kinds of fish
Andre Thuronyi has been working in this region for some 30 years, and now runs the Araras Eco Lodge, sharing his passion for the Pantanal's environment with visitors from around the world.
While he says the wetlands are largely well preserved, he now sees a growing threat from the surrounding high lands and plateaus.
"The real danger is in the area around the Pantanal, in the tablelands, due to the very strong agricultural movement, agribusiness, soya plantations, sugar cane plantations," he says.
"All the waters that flow into the lowlands of the Pantanal come from the tablelands. They use different chemicals that sooner or later might flow into our rivers."
Concern over farming
Environmentalists say another threat to the region is farming activity, which uses inappropriate soil management, and does not follow environmental legislation.
Much of the work in the Pantanal is still done by cowboys
The erosion this has caused has led to a "drastic increase" in sediment in some areas of the wetlands which can have extremely damaging consequences.
Paulo Teixeira who works at the Pantanal Research Centre in the city of Cuiaba points to the example of the Taquari river basin where an area of 5,000 square kilometres was flooded.
"Pantanal half of the year is dry, half of the year is flooded," he says. "This is what causes the uniqueness and environmental richness of the area.
"In the case of the Taquari river, it meant that in some parts of the Pantanal it has been flooded the whole year, so it destroyed the way of life of many farmers, and of course it is affecting biodiversity standards."
Poor farming practices are not the only danger. In some nearby cities only 20% of the sewage is treated, and waste and rubbish can be seen floating down the river towards the Pantanal.
Pollution from untreated sewage and rubbish is a concern
Intensive cattle farming is said to have caused deforestation in the region, while environmentalists warn that hydroelectric plants are affecting the "flood pulse" of the wetlands.
But Mato Grosso's Environment Secretary Luis Henrique Daldegan says the state is aware of the importance of the Pantanal and is working hard to address these kinds of problems.
It is possible, he says, to reconcile development with protecting the environment.
"It is very clear that agricultural activities, when they are not done properly, can cause irreversible harm," he told the BBC News website.
"What we have to do, and we are doing, is to ensure that good agricultural techniques help to mitigate this overall, in order to protect the Pantanal. This is what we have to do to protect the wetlands and to have sustainability in our production and our ecosystem."
The concerns about ethanol production in the highlands are dismissed by those involved in the industry, although there are signs of tension within the government.
Agricultural Minister Reinhold Stephanes has been reported as suggesting there could be an expansion of sugar cane plantations in the highlands, while Environment Minister Carlos Minc has said the possibility of this happening is "zero".
At the Itamarati ethanol plant, production of the biofuel that Brazil has championed around the world continues 24 hours a day.
In the nearby fields there is sugar cane for as far as the eye can see, but a government plan setting out new limits on where more plantations or refineries might be permitted has now been delayed for many months.
The plant's chief executive Sylvio Coutinho says new technology means there should not be any risk in expansion, even in the region above the wetlands.
A caiman rests among the vegetation
"If they come to destroy the environment, then clearly no, if they come to generate wealth in harmony with the environment, why not?" he argues.
"There is technology for that these days. I think instead of emotion, we need to focus instead on an explanation from biologists who know the subject, to see what really causes pollution.
"We cannot let the Pantanal be polluted and destroyed."
At the end of a long day in the Pantanal, along the road which crosses through the wetlands, you can see dozens of caimans, an alligator-like animal basking in the setting sun, while birds feed in the waters just a short distance away.
The diversity of animals and plants is truly extraordinary.
Life in the wetlands still seems relatively untouched, but those who love this rich and unique ecosystem say it is only with continued vigilance that it will be preserved.
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