The loss of such huge areas of the forest would result in the eradication of species, many of which are yet to be studied, but would also unleash vast amounts of stored carbon.
Such devastation could spell catastrophe for the planet due to the implications for climate change.
Thousands of fires are racing through the Amazon, with Brazil recording more than 75,000 individual forest fires in the first eight months of the year.
In July, the rate of deforestation equated to roughly an area the size of Manhattan every day, or the size of Greater London every three weeks.
Professor Thomas Lovejoy of George Mason University, who has studied the Amazon since 1965, told The Independent there are signs it is on course for further extensive deforestation which will soon stretch beyond human control.
The previous research of his colleague Carlos Nobre indicates further razing could break the Amazon’s hydrological cycle, whereby it generates half its own rainfall. If a critical amount of trees are felled, the ecosystem will degrade to the point of being unable to support the rainforest.
But speaking to The Independent on Friday, Professor Lovejoy said things have since become much worse.
“When we were first worried about it, the amount of deforestation was small,” he said. “But then these other things started to interact – the impact of deforestation and the effects of climate change became apparent, and the extent of the use of fire [for clearing land] became apparent.
“The reason we believe the tipping point is so close is because we’re seeing historic droughts in 2005, 2010, and 2016. And satellite images in the north central Amazon also show forests remote from everything are beginning to convert into grassland. That’s yet another symptom.
“These are not little droughts – boats cannot get up some of the river’s tributaries, because they’re so dry.”
Professor Lovejoy said such a conversion from rainforest to savannah and scrubland would be the wider effect if a tipping point is reached.
“You’d have extensive parts of the southern and eastern Amazon and parts of the central converting to savannah, and maybe to even drier conditions.”
As well as the catastrophic loss of the rainforest as a massive carbon sink, Professor Lovejoy said losing swathes of the Amazon would result in a huge loss in the planet’s biodiversity.
“People don’t really grasp that the biodiversity in one part of the Amazon is very different to that in other parts,” he said.
“So if you have regional loss, you’ve having actual total loss of that biodiversity. It’s the largest terrestrial repository of biodiversity on the planet, so all that will impact the future of Brazil, the economy, for the future of the world, vanishes.
“We tend to live in the delusion we don’t depend on the biology of the planet, but we do. Agriculture, forestry, medicine, all of that has a major biological base. Scientists are revealing new potential all the time. But you can’t do that if the species isn’t there to study. It’s like book burning on a very grand scale.”
He added: “The standing forest is absorbing carbon on an annual basis, but its even greater importance is in the total amount of carbon stored in the forest itself. Tropical rainforests store more carbon per unit area than basically any other kind of habitat. So it’s folly in the end.”
Asked if he thought Brazilian president Jair Bolsonaro was a threat to the future of life on our planet, Professor Lovejoy said: “He certainly is, and he’s also a threat to Brazilian agriculture.”
But he said judging by the amount of public concern in Brazil, he believes things can change, despite Mr Bolsonaro’s policies.
“When there’s so much smoke in Sao Paolo, the street lamps come on at three in the afternoon, it’s clear there’s a problem.
“The world doesn’t expect Brazil to manage this all completely on its own, the world would like to help. And we hope we will be welcomed into some kind of partnership.”
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