IT IS perhaps the most iconic symbol of life on our planet. The Amazon is the world’s largest and most biodiverse tropical rainforest, and an immense trap for carbon dioxide. The perils of deforestation in this vital resource are old news. But now, the time on the clock is running out. It seems that the world’s biggest rainforest is about to turn into the world’s biggest environmental disaster. “We are about to collapse,” says Luciana Gatti at Brazil’s National Institute for Space Research. “We are in an emergency, we need action now.”
Gatti has spent years observing the Amazon from the air. She believes we are as little as five years from a point of no return, where lush rainforest irreversibly begins to convert into dry savannah. It is also the point at which billions of tonnes of carbon would be dumped into the atmosphere. “It’s a nightmare,” she says.
That nightmare scenario is the infamous Amazon tipping point, where the ecosystem can no longer cope with the damage being inflicted and irreversibly flips into a new stable state. Like a game of Jenga, brick after stabilising brick is removed until the tower collapses in a heap.
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Warnings that this is approaching have now taken on extreme urgency. The rate of deforestation has increased sharply and is fast approaching the theoretical limit. In September, the Science Panel for the Amazon (SPA) – a group of more than 200 experts including Gatti – . The verdict: we are on the edge of disaster.
Scientists first began to seriously worry about a potential Amazon tipping point in about 2000, when modellers at the Met Office Hadley Centre in the UK change and deforestation could cause the rainforest to dry out.
A few years later, a team of Brazilian scientists including Carlos Nobre, who is now co-chair of the SPA, . Their model estimated that in central, southern and eastern parts of the Amazon, a loss of 40 per cent of forest cover from pre-industrial levels – or 3’C of warming – would reduce rainfall so much that the rest of the forest would die of thirst and turn into savannah in less than a decade. They dubbed this irreversible process “savannisation”.
Nobre has since , partly to factor in the global warming that has happened since 2000. The Amazon is already 1.2°C warmer than it was in pre-industrial times and is warming three times faster than the global average. At that level of warming, between 20 and 25 per cent deforestation would deliver the coup de grace.
Either way, we would be , says Nobre, “for the common-sense reason that there is no point in discovering the precise tipping point by tipping it”.
That magic number is fast approaching. The SPA says that 17 per cent has already been lost and a further 17 per cent degraded. According to Tasso Azevedo, part of the MapBiomas project, which has been monitoring land-use change across the Amazon since 1985, at current rates of deforestation we will hit 20 per cent overall by the end of this decade. In Brazil, the number is already 19 per cent. And a report earlier this month put .
The key to understanding the game of Amazon Jenga is the interaction between trees and water. “It’s all about what trees and leaves do, which is to promote the evaporation of water,” says SPA member Thomas Lovejoy at George Mason University in Fairfax, Virginia. “They are very powerful movers of water.”
In an intact Amazon, water vapour blowing in from the Atlantic Ocean on the prevailing easterly winds joins an atmosphere already laden with moisture. About a third of it is there because of evapotranspiration: trees siphoning water out of the soil and releasing it into the air from their leaves. The air periodically becomes saturated, the moisture falls as rain, and the cycle starts over. This hydrological cycle is central to the health of the Amazon ecosystem, says Nobre. Not only does it keep the forest wet and the rivers full, it also has a cooling effect.
As tree cover is lost to cattle ranching, soya bean plantations, mines, roads, urban sprawl and wildfires, however, the hydrological cycle is enfeebled. The remaining forest begins to dry out and, as evapotranspiration declines, temperatures rise. Trees stressed by drought and heat reduce their rate of photosynthesis and stop absorbing CO2. Their leaves turn brown and fall off; entire trees die. The resulting leaf litter and wood decomposes and emits CO2. It also dries out and becomes a tinder box. Fires are started deliberately or break out naturally, destroying yet more cover. “It’s a domino effect,” says Nobre.
“The Amazon is warming three times faster than the global average”
This cycle is especially vicious in the dry season. In the southern Amazon, natural annual climate oscillations create a relatively dry period from September to November. An intact forest is wet enough to ride out the dry season or a drought, but where trees are already stressed, the extra dryness and heat can be lethal. The dry season is also lengthening because of the disruption of the hydrological cycle, exposing vulnerable trees to more sustained stress. Yet another Jenga piece is lost.
Parts of the Amazon are already showing signs of a severely disrupted hydrological cycle, says Nobre. “The dry season in the southern Amazon is three to four weeks longer than in the 1990s, two to three degrees warmer and 20 to 30 per cent drier,” he says. This combination of warming, drought and forest degradation has led to a severe increase in vulnerability to fires, he says.
“The south-east of the Amazon has flipped from being a carbon sink to a carbon source”
There are other warning lights flashing. Severe droughts used to strike about once every 20 years. They are now a twice-a-decade phenomenon, with droughts in 2005, 2010, 2015-16 and 2020. Across the Amazon, the , a sign that they are being pushed beyond their natural biological limits. In the central Amazon, repeatedly burned areas of forest are failing to regenerate and are . Meanwhile, “animal species typical of the savannah are starting to “, says Nobre. Savannisation is under way.
The most ominous warning yet was . A team led by Gatti spent nine years flying small planes over four regions of the Amazon – the north-east, south-east, north-west central and south-west central – taking samples of the air and monitoring the temperature, the moisture content of the soil, how much had been burned and the greenness of the canopy.
Over the course of the study, which ran from 2010 to 2018, they saw some dramatic shifts. “The rainfall has reduced a lot, the temperature has grown a lot, and the forest felt it,” says Gatti.
Fatal blow
The hardest-hit areas were in the east. By 2018, the north-east study area was 37 per cent deforested and the south-east 28 per cent. Over the nine years, dry-season rainfall fell by 20 to 30 per cent and the average dry-season temperature rose about 2°C. In the south-east, in particular, where there is an “arc of deforestation” because of encroaching cattle and soya, this is delivering a fatal blow to the forest. “The forest is now more dying than growing,” says Gatti. As a result, the south-east has flipped from being a carbon sink to a carbon source. Rather than soaking up some of our emissions, it is adding to them.
“This is the most troubling element,” says Nobre. And the situation is getting worse. According to Gatti, in the 50 years up to 2018, the Amazon lost about 17 per cent of its forest cover. In the past three years, the rate of deforestation has accelerated dramatically and a further 1.5 per cent is being destroyed a year. Parts of the east are now 40 per cent farmland and she says she wouldn’t be surprised to see 50 per cent. “This is amazing, crazy deforestation,” she says.
Given the levels of deforestation in the southern Amazon, it isn’t unreasonable to argue that these changes signal that, in this region at least, the point of no return is approaching. “Putting all these things together we can say we are very, very, very close to this tipping point,” says Nobre. “Some scientists believe the tipping point may have already been exceeded in portions of the Amazon.”
Lovejoy shares the sentiment. “We’re seeing the ecological system of South America begin to come apart,” he says.
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What would that mean? According to Nobre, once the threshold is exceeded, the forest will degrade further even without any more active deforestation. Eventually, over the course of years or decades, up to 70 per cent of the Amazon rainforest will flip to dry savannah. Not everything will go. “We are only going to have remaining forest near the Andes where the concave shape of the Andes makes for very high levels of rainfall,” says Nobre.
But that won’t save the Amazon, and indeed the rest of the world, from disaster.
The Amazon covers an area of about 5.5 million square kilometres, more than 20 times the area of the UK, and holds around 10 per cent of the world’s species, a quarter of them found nowhere else. It is a hotbed of cultural diversity, with 30 million people from more than 350 ethnic groups. It also supplies the world with a vital ecosystem service in the form of carbon sequestration. According to Gatti, the forest stores at least 100 billion tonnes of carbon above and below ground.
The loss of 70 per cent of the Amazon will deposit more than 50 billion tonnes of that stored carbon into the atmosphere, according to Nobre – equivalent to roughly six years of global carbon emissions from the burning of fossil fuels and a tenth of what we can still afford to emit from now on to give ourselves a . That would make reaching the Paris Agreement target of no more than 1.5°C of warming almost impossible, says Nobre.
“If we lose the Amazon, the global temperature can grow 0.25 degrees,” says Azevedo. That would be bad enough, but the added fear is that it could , such as the thawing of the Arctic permafrost or the loss of an Antarctic ice sheet.
“These things are very dangerous because they can create a cascading effect that will impact the whole basis of the biosphere,” says , director-general of the Center for International Forestry Research in Indonesia.
At the very least, the loss of a major chunk of the Amazon could do irreparable harm to neighbouring ecosystems of international importance, including the high Andes and the tropical savannah of the Cerrado.
Amid all this gloom, however, are reasons for hope. , Irvine, points out that the 20 to 25 per cent figure comes from computer models that are inherently uncertain. One especially thorny factor is rising levels of CO2, which boosts the growth of vegetation and may offset the deforestation somewhat. Models that leave this out produce tipping points at 20 to 25 per cent, but throw it in and you suddenly get a wider range of outcomes.
The claim that the tipping point lies somewhere between 20 and 25 per cent thus remains a hypothesis, says Brando – albeit a plausible and scary one. “If it’s supported by observation, we are in huge trouble,” he says. “The changes that we’re seeing today are in agreement with predictions. But to jump from there and say that we have initiated this snowball effect that would lead to savannisation of the Amazon, there are large uncertainties.” Nonetheless, he still supports urgent action. “The tipping point is something that we don’t want to find out by doing.”
Some scientists are wary of crying “tipping point” at all. “I think we in general have to be careful about throwing that phrase around, it’s kind of dangerous,” says Scott Denning, an atmospheric scientist at Colorado State University who wrote a . In the context of the Amazon, it wrongly suggests that the entire forest is doomed, he says. He does accept that the south-east region has crossed a dangerous threshold where it no longer helps to soak up our carbon emissions. But that isn’t the same as total collapse.
The Amazon also emits a lot of the potent greenhouse gas methane, mostly from its wetlands. It isn’t clear what would happen to this under savannisation, but it is reasonable to assume that levels would fall.
Window of opportunity
Even if we are approaching a tipping point, it isn’t too late. “There is a narrow window of opportunity to change this trajectory. But action must be exponential,” says Mercedes Bustamante at the University of Brasilia, who is a member of the SPA.
Many other scientists express similar sentiments. But if the worst is to be avoided, the rescue plan must be swift and decisive. The absolute priority is to restore the hydrological cycle, says Lovejoy, by stopping further degradation and replanting trees.
The minimum requirement for that is an immediate halt to deforestation, says Nobre, followed by a huge reforestation effort. In some places, that means tree planting, in others passive rewilding. “When forests are degraded, they are not gone,” says Brando. “They have an amazing ability to bounce back.”
Similar efforts to – which is separate from the Amazon – are proving unexpectedly successful. Regrown forest isn’t quite as biologically rich as virgin rainforest, but it can still hold 70 to 80 per cent of the carbon and 65 per cent of the biodiversity of a primary forest, says Nobre.
Another minimum requirement is law enforcement, says Bustamante. “Amazon countries have good environmental laws but they need to enforce them.” Brazilian law allows no more than 20 per cent deforestation of a given area, says Gatti, but as her research has found, this is routinely flouted. About 10 per cent of deforestation is illegal, often aided and abetted by corrupt regional politicians, says Rodrigo Botero García at the in Colombia.
If the situation is stabilised, next comes the long, hard slog of building a new Amazon economy based on agroforestry, which means rearing livestock and growing high-value crops such as cacao under the canopy of a secondary forest – one that has regrown after tree loss. That has the added advantage of benefiting the locals, including Indigenous people, rather than multinational agribusiness companies. “Most of the profits from the existing Amazon economy leaves the Amazon,” says Nobre.
The ranchers, soya bean farmers and even Brazil’s deforestation-denying president Jair Bolsonaro seem to be waking up to the situation. Beef and soya farmers, who Nobre says are collectively responsible for 90 per cent of Amazon deforestation, have already noticed that disrupting the hydrological cycle isn’t a sensible long-term strategy. “Agribusiness is already starting to have big economic problems with reduction in precipitation and drought,” says Gatti.
The big companies are also responding to international pressure, says Brando. Many have spent years building the trust of buyers and the confidence of consumers and don’t want their reputations trashed along with the forest. At COP26 in November, Brazil signed the Glasgow Leaders’ Declaration on Forests and Land Use, which commits signatories to end deforestation by 2030. “We are happy that Brazil signed the forest pledge,” says Ane Alencar, science director at . “I want to believe, but we want to see more concrete steps, we want to see a very detailed plan. We need to demonstrate as a country that we can reduce deforestation.” Brazil already appears to be backtracking on its pledge by claiming, erroneously, that it only applies to illegal deforestation, says Alencar.
And even if Brazil does end deforestation by 2030 the forest is so degraded in places that it will continue to emit CO2 for many years, says Paulo Netto at the University of Sao Paulo. From scientists and activists alike, the message comes across loud and clear: the Amazon is in serious trouble and accelerating towards the brink, but where there is life there is hope. “We cannot be the prophets of doom. We have a moral obligation to remain optimistic and to try to do something,” says Nasi. “The future is not written, the future is what we do.”
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