The largest rainforest in the world is already under pressure from climate change, deforestation, biodiversity loss and extreme weather.
Researchers analysed data on five key drivers of water stress in the Amazon and looked at how these pressures could lead to “local, regional or even biome-wide forest collapse”.
The new study, published in Nature, finds that by 2050, between 10 and 47 per cent of the Amazon forest will be exposed to “compounding disturbances” that “may trigger unexpected ecosystem transitions”. This could result in large swathes of lush rainforest shifting to dry savannah.
One author of the study tells Carbon Brief that this prospect by mid-century is “very scary”.
The study notes that the complexity of the Amazon “adds uncertainty about future dynamics” and that there are still “opportunities for action”.
The findings highlight the likelihood that “climate change will continue to affect the forest in very unpredictable ways”, a scientist not involved in the study says.
Amazon pressures
The Amazon forest stores a huge amount of carbon and houses at least 10 per cent of the world’s biodiversity. It faces an uncertain future largely due to the effects of deforestation and climate change.
Last year, the Amazon river basin experienced an “exceptional drought” that was 30 times more likely to occur due to climate change, a rapid attribution study found.
Around 20 per cent of the Amazon has already been deforested and a further 6 per cent is “highly degraded”.
According to several studies, the Brazilian section of the Amazon is now an overall net “source” of carbon, rather than a “sink”, due to a number of factors including deforestation.
Scientists have long warned that climate change and human-driven deforestation could push the Amazon rainforest past a “tipping point” – a threshold that, if crossed, would see the “dieback” of large amounts of dense Amazon rainforest and a shift into permanent, dry savannah.
This would be characterised by a mixed tree and grassland system with an open canopy that allows the soil to become much hotter and drier.
Previous studies suggest that the Amazon could be pushed beyond this tipping point if forest loss exceeds 40 per cent. Other research published last October found that recent drying over the Amazon could be the “first warning signal” that the rainforest is approaching a tipping point.
The new study examines five key drivers of water stress in the Amazon – global warming, annual rainfall, rainfall seasonality intensity, dry season length and accumulated deforestation – to estimate the critical limits of these issues for the Amazon.
The researchers use existing evidence from palaeorecords, observational data and modelling studies. For example, they find that rainfall levels below 1,000mm each year could result in “forests becom[ing] rare and unstable”.
For floodplain ecosystems, this critical threshold was estimated at 1,500mm per year. This implies that “floodplain forests may be the first to collapse in a drier future”, the study says.
Based on this analysis, the researchers estimate that these drivers could, in combination, potentially lead to a large-scale Amazon tipping point by 2050.
Dr Bernardo Flores, the lead author of the study and a researcher at the Federal University of Santa Catarina, Brazil, says the study aims to show the effects of these combined pressures. He tells Carbon Brief:
“It is surprising how the combination of stressors and disturbances are already affecting parts of the central Amazon… [which] can already transition into different ecosystems.
“Then, when you put everything together, the possibility that by 2050 we could cross this tipping point, a large-scale tipping point, is very scary and I didn’t really think it could be so soon.”
Ecosystem transitions
The findings highlight how the combination of different disturbances – such as intensified droughts and fires – could trigger “unexpected ecosystem transitions even in remote and central parts” of the Amazon.
Flores says that most of the Amazon is warming “significantly” and many areas are becoming drier than in previous years, adding:
“When you combine this with things like deforestation, fires and logging…when these disturbances act together, they can have a synergistic effect.”
These issues occurring at the same time “could cause large parts of the Amazon to transition into a different ecosystem”, Flores says. He tells Carbon Brief:
“When you lose more forest, you could cross that tipping point in forest loss and then trigger a large-scale tipping point when the whole system would start accelerating to a large-scale collapse.”
The study finds that around half (47 per cent) of the Amazon biome has a moderate potential for these changes. Larger, remote areas covering 53 per cent of the Amazon have a low chance of ecosystem transition – which mostly accounts for protected areas and Indigenous territories.
Within these figures, the researchers find that 10 per cent of the Amazon has a “relatively high transition potential” – meaning that it is already seeing more than two types of disturbances.
The study then looks at the three “most plausible” trajectories for Amazon ecosystems impacted by compounding stressors. These are: degraded forest, white-sand savannah and degraded open-canopy ecosystem.
Using examples of existing “disturbed” forests across the Amazon, the researchers identify these as possible futures for different parts of the forest. The figure below shows the different disturbances and feedback loops in each of these ecosystems.
Alternative ecosystem trajectories for Amazon forests that could transition due to compounding stressors. These are: white-sand savannah (left), degraded open canopy (centre) and degraded forest (left). The image shows disturbances, feedbacks and an image of the alternative state in each case. Source: Flores et al (2024)
1.5C ‘safe boundary’
Prof Dominick Spracklen, a professor of biosphere-atmosphere interactions at the University of Leeds, who was not involved in the study, says the research “highlights the urgency to keep both global warming and deforestation within safe limits” to protect the Amazon.
Based on their analysis, the authors say that staying within 1.5C of global warming (the aspirational limit included under the Paris Agreement) is a “safe boundary” for the Amazon forest to avoid large-scale transformations.
(A 2020 study concluded that there is a “significant likelihood” that multiple tipping points will be crossed around the world if temperatures exceed 1.5C.)
The new study suggests that ending deforestation and forest degradation – alongside boosting restoration in degraded areas – are key factors in improving the state of the Amazon.
However, Flores notes that action to stop deforestation without also stopping greenhouse gas emissions may be “useless” to prevent the forest reaching a major tipping point.
The rate of deforestation in Brazil’s Amazon soared under former president Jair Bolsonaro, but has almost halved in 2023 since Luiz Inácio Lula da Silva took over office. Meanwhile, forest loss in the Bolivian sections of the Amazon reached record-high levels in 2022.
Spracklen says this disparity “highlights the need for a pan-Amazon alliance to help collaboratively reduce deforestation”. (Last year, the leaders of the eight Amazon basin countries committed to work together to protect the rainforest – but stopped short of agreeing to end deforestation.)
Dr Patricia Pinho, the deputy science director at the Amazon Environmental Research Institute (IPAM), who was not involved in the study, says that more research is needed to assess the “cascading” effects of tipping points for people living in forest regions. She tells Carbon Brief:
“From the point of view of some people in the Amazon…A tipping point of the forest has been reached already. People are already feeling the limits of cultivating their traditional foods or encountering the biodiversity that they use for rituals, for tradition, for foods, for medicine.”
Another study author, Dr David Lapola, a researcher at the University of Campinas in Brazil and a Carbon Brief contributing editor, says the research was “necessary to investigate other potential drivers” towards this tipping point. He adds:
“Of course, there needs to be more research because even though the article points out possibilities, there is still a lot of uncertainty surrounding how the tipping point would operate and the chances of it [happening].”
Pinho adds that the “quite depressing” findings raise a lot of “red flag” issues around the Amazon, saying:
“If we don’t [take] action right now as soon as possible to avoid greenhouse emissions… climate change will continue to affect the forest in very unpredictable ways.”
She says the study is a “great contribution” to Amazon tipping point research, noting that “the bad news is that we are approaching sooner than expected those critical transitions”.
This story was published with permission from Carbon Brief.
