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At around 5.5 million square kilometers, almost twice the size of India, it covers around 40 percent of South America and is home to at least 10 percent of the planet’s known species, along with around 30 million people from more than 350 different ethnic groups.
The Amazon is also one of our most important defenses against climate change. It stores around 150 to 200 billion tons of carbon, roughly equivalent to four to five years’ worth of global carbon emissions from the burning of fossil fuels.
But humans are slowly tearing it down to make room for agriculture, ranching and mining. The Amazon has already lost 18 percent of its tree cover, and it’s losing an extra 1 percent roughly every three years. Many scientists now believe it could soon reach a tipping point where it starts to dry up and can no longer function as a rainforest – a process known as dieback.
What is a rainforest?
As the word suggests, a rainforest is a mostly evergreen forest that receives large amounts of rainfall. Rainforests are found on every continent except Antarctica and are home to more than half of the world’s known species – despite covering just 6 percent of the Earth’s surface.
There are two types of rainforest: temperate and tropical. The Amazon is by far the world’s largest tropical rainforest, with more than three times as much primary forest as the next largest, the Congo Basin.
Rainforests often sustain themselves through self-watering. The heat and humidity of tropical rainforests leads to frequent and intense rainfall. Plants soak up the rainwater and then release it back into the atmosphere through evaporation and transpiration, which in turn helps keep the climate rainy and humid. Through this cycle of precipitation and evapotranspiration, rainforests can generate up to 75 percent of their own rain.
But deforestation poses a major threat to rainforests across the globe. As tree cover decreases, transpiration also falls, and eventually, the rainforest can no longer produce enough rainfall to sustain itself. The regional climate becomes drier, causing more trees to die out and leaving behind a dry, degraded landscape.
Climate tipping points
Rainforest dieback is a prime example of a climate tipping point: a small shift in the climate system that could have drastic long-term consequences for the entire planet.
Think of it like a game of Jenga: by cutting down trees and emitting greenhouse gases into the atmosphere, we’re removing blocks from the tower and placing them on top. As the Earth heats up, the tower becomes increasingly unstable – until it can no longer support itself and collapses.
In 2019, a team of climate scientists identified nine key tipping points in the climate system, including Amazon dieback, the melting of the Greenland and Antarctic ice sheets, and the collapse of the Gulf Stream. Crossing any one of these thresholds would likely cause the climate crisis to accelerate rapidly and irreversibly and could even trigger other tipping points, causing a domino effect.
Unfortunately, scientists believe the Amazon is only 15 to 20 years away from reaching a tipping point where it starts to permanently dry out. In some parts of the rainforest, deforestation is already nearing 40 percent, while the climate crisis is also making the region hotter and drier, causing many trees to die off.
“In the southeastern Amazon, temperatures during August and September have increased by 3.21 degrees Celsius in the last 40 years,” said leading Amazon expert Luciana Gatti in a recent GLF Live. “This is a nightmare. Tree mortality is two to three times higher than in other parts of the Amazon.”
Trees absorb carbon through photosynthesis and emit carbon through respiration, as well as through decomposition when they lose foliage or die entirely.
“Each dry season, the trees undergo more stress,” Gatti explained. “Many leaves fall; they stop carrying out photosynthesis and start to decompose.
This dieback, Gatti says, is causing around a third of the carbon emissions in the southeastern Amazon.
“This means that the forest is dying more than growing. This says we are in an emergency in this part of the Amazon.”
Crossing the Amazon tipping point
If the Amazon were to undergo dieback on a large scale, it would release much of the carbon that it currently stores into the atmosphere, exacerbating the climate crisis.
“The eastern Amazon, which is 27 percent deforested on average, emits 10 times more carbon than the western part, which is 11 percent deforested,” said Gatti. “By deforesting the Amazon, we are accelerating climate change because we are sending more carbon dioxide into the atmosphere, reducing precipitation and increasing temperatures.”
A hotter and drier climate would lead to more frequent wildfires, causing yet more carbon emissions. “Hot and dry conditions make the forest more flammable, explained Gatti. “These fires represent instantaneous carbon dioxide emissions, but later it causes further emissions through decomposition.”
It would also mean more frequent drought, threatening the food security of Amazon communities, as well as the loss of biodiversity and ecosystem services like pollination, clean water and recreation.
The effects of Amazon dieback are likely to be felt even thousands of kilometers away: the trees in the Amazon provide moisture that is transported by the wind across the Americas and possibly even as far as the midwestern U.S. By disrupting global water cycles, the collapse of the Amazon is likely to cause more frequent droughts and lower crop yields across the Western Hemisphere and other parts of the world.
These changes could cause some USD 3.6 trillion in damage to the global economy within 30 years – and they could take centuries to reverse, if they can be reversed at all.
Worryingly, the Amazon’s climate is already showing early signs of drying up. Since the 1980s, scientists have observed a significant increase in the vapor pressure deficit over the tropical parts of South America. There are three possible explanations: first, the climate crisis is leading to reduced rainfall; second, transpiration is decreasing due to higher concentrations of carbon dioxide in the atmosphere; and lastly, deforestation is also resulting in lower evapotranspiration ,and hence less moisture is entering the atmosphere.
A ticking time bomb
Worryingly, the Amazon is already emitting more carbon dioxide than it absorbs. Most of these emissions are a result of fires, many of which have been set deliberately by humans to clear land for farming and cattle ranching.
In Brazil, which accounts for 60 percent of the Amazon, deforestation has soared under President Jair Bolsonaro, who has weakened environmental protections and encouraged development in the Amazon since taking office in 2019. Brazil’s deforestation rates are now at their highest in 12 years.
“In the 50 years leading up to 2018, the Brazilian Amazon was 17 percent deforested, but the mean deforestation for 2019 to 2020 was 1.5 percent per year,” said Gatti. “Very soon, we will have deforested 5 percent in just five years. This is an amazing increase in deforestation.”
According to the UN, the world is on track for over 3 degrees Celsius of warming by 2100 – and world leaders are doing nowhere near enough to prevent that from happening. New climate targets from rich countries like the U.S., Canada, Japan and the U.K. are still only enough to limit global warming to 2.4 degrees – and there has been little policy support to achieving those targets.
The only solution, Gatti believes, is a complete and immediate moratorium on deforestation in the Amazon. “Don’t talk about legal or illegal – it doesn’t matter. Zero deforestation. And no fires during the dry season, when the forests are very dry and can burn much more vegetation.”
But a ban on deforestation would not be enough to enable the Amazon to start to regenerate. “In these regions where the deforestation is more concentrated, we need to have a program to reforest,” said Gatti.
“We need to recognize that people are deforesting because they want opportunities to have economic activities, so we need a green economy, a sustainable economy. We need to bring all sectors of a population into it: agribusiness, scientists, technicians, NGOs, lawmakers. It’s like a societal agreement because this is the future of society.”