Climate change: Amazon rainforest will die by 2064, says scientist

South America’s Amazon rainforest will be wiped out by 2064 due to deforestation and prolonged droughts from climate change, a scientist predicts in a new paper.

At about 2.3 million square miles, the Amazon is the largest tropical forest on Earth.

As well as reducing air pollution and regulating the world’s oxygen and carbon cycles, it creates its own precipitation to sustain local populations with freshwater.

But it stands on the verge of a ‘tipping point’ as a consequence of human-caused disturbances, ‘for which we are all responsible’, according to Robert Walker, a professor of geography at the University of Florida.

Professor Walker says the Amazon will transition over the next few decades from a dense, moisture-filled forest to an open savannah, dominated by flammable grasses and shrubs.

He added that the local people’s dependency on the Amazon as a source of water means ‘the magnitude of the catastrophe will be worse than heretofore imagined’ in, at the very most, 44 years’ time.

2064 marks the point at which ‘a tipping point’ is reached, where extreme droughts become too frequent for canopy to completely recover from them (something that currently takes about four years).

A ‘collapse’ of environmental governance in Brazil and other Amazonian nations has renewed public concerns about the fate of the forest, as highlighted by Professor Walker in his paper, published in the journal Environment.

‘It is doubtful that the Amazonian forest will remain resilient to changes in the regional hydroclimate,’ he writes.

‘The biggest concern involves intensification of drought-based tree mortality stemming from the synergies of fire, deforestation, and logging.

‘The development of Amazonia now lies on a collision course not only with the interests of conservation but also with the welfare of the very people it is meant to benefit.’

Deforestation – the permanent removal of trees – is a major environmental issue, causing destruction of forest habitat and the loss of biological diversity.

A big driver of deforestation is the deliberate ignition of the rainforest’s canopy to clear space for agricultural crops.

Amazonian fires famously intensified last year – in August 2019, the National Institute for Space Research in Brazil reported more than 80,000 fires across all of the country, a 77 per cent year-on-year increase.

‘A generalised collapse of environmental governance in Brazil and other Amazonian nations has renewed public concerns about the fate of the forest,’ says Professor Walker.

‘These concerns – recently intensified by Amazonian fires in the summer of 2019 –have put the focus on regional climate changes capable of inducing a “tipping point” beyond which the moist forest transitions to a tropical savanna.’

Shortly after the turn of the millennium, effective environmental policies in Brazil reduced deforestation rates in the Amazon Basin, which is home to the rainforest.

But these policies ‘began to unravel at almost the same time they proved effective’ and deforestation numbers started to climb after reaching a low point in 2012, Professor Walker says.

There is also mounting evidence that deforestation affects regional climate by reducing precipitation and by lengthening the dry season.

The researcher also points to ‘waves of in-migrants’ that initiated a process of agricultural development in the late 1970s, which has to date consumed about 20 per cent of the Brazilian portion of the original forest.

However, poverty and poor use of government resources ultimately drives much of the deforestation, Professor Walker suggests.

‘The people there, they don’t worry so much about biodiversity, the environment, when they have to worry about eating their next meal,’ he told United Press International.

Meanwhile, more frequent spells of drought caused by global warming are killing off the most vulnerable tree species in the Amazon, arising from water and thermal stress.

What’s more, drought severely comprises the ability of surviving trees to do their job as the lungs of the world.

The Amazon rainforest absorbs large amounts of carbon from carbon dioxide (CO2) – a major contributor to climate change.

Scientists estimate that the Amazon takes in as much as one-tenth of human fossil fuel emissions during photosynthesis.

But the rainforest experienced serious episodes of drought in 2005, 2010 and 2015, and studies show its trees absorb a tenth less CO2 from the atmosphere during droughts.

A single season of drought in the Amazon rainforest can reduce the forest’s carbon dioxide absorption for years after the rains return.

Dr Adriane Muelbert, an expert from the University of Leeds who was not involved with Professor Walker’s research, previously said the ecosystem’s response is lagging behind the rate of climate change.

‘Droughts that hit the Amazon basin in the last decades had serious consequences for the make-up of the forest, with higher mortality in tree species most vulnerable to droughts and not enough compensatory growth in species better equipped to survive drier conditions,’ she said.

If dry seasons in the Amazon continue to lengthen as over the past few decades, the drought of 2005 will become the region’s ‘new normal’ before the end of the century, Professor Walker believes.

The return period of serious drought once gave canopies sufficient time to recover from fire, but the lengthening dry season has ‘begun to squeeze away this respite’.

‘A forest cannot survive if its canopy needs more than four years to recover from a yearly event,’ he says.

‘In fact, southern Amazonia can expect to reach a tipping point sometime before 2064 at the current rate of dry-season lengthening.

‘By then, the return cycle of severe drought will have dipped below the time needed for the canopy to recover, at which point the forested landscape, denuded by fire, will be permanently invaded by flammable grasses and shrubs.’

Elsewhere in the paper, Professor Walker refers to the Anth­ropocene era – a proposed geological epoch in which human permanently changed the planet.

‘The Amazonian environment has proven resilient to long swings of climate change that can be tracked through the geologic record extending over millions of years.

‘Even during periods much warmer than today, the forest held its ground, with some encroachment of tropical savanna along the Basin’s rim to the south and east, now known as the arc of deforestation.’

‘Will the Anth­ropocene act with greater force, triggering a tipping point transgression at basin scale?,’ he asks.

‘Whatever the answer, the evidence is indisputable that Amazonia’s climate is now changing.’