Amazon rainforest may be approaching critical tipping point, study finds

The Amazon is losing its ability to recover from disturbances such as droughts and land use changes, scientists reported on Monday, addi...


The Amazon is losing its ability to recover from disturbances such as droughts and land use changes, scientists reported on Monday, adding to concern that the rainforest is approaching a critical threshold beyond which a much of it will be replaced by grassland, with far-reaching consequences for biodiversity and climate change.

The scientists said their research had not determined when this threshold, which they described as a tipping point, might be reached.

“But it’s worth remembering that if we get to this tipping point, that we commit to losing the Amazon rainforest, then we’re getting a meaningful payback on global climate change,” said one of the scientists, Tim Lenton, Director of Global Systems. Institute of the University of Exeter in England.

The loss of rainforest could release up to 90 billion tonnes of heat-trapping carbon dioxide into the atmosphere, equivalent to several years of global emissions. This would make it more difficult to limit global warming.

Among previous studies, there was a high degree of uncertainty about when such a threshold might be reached. But some research has concluded that deforestation, drying and other factors could lead to substantial forest dieback in the Amazon by the end of this century.

Carlos Nobre, a senior scientist at the National Institute of Amazon Research in Brazil and one of the first to sound the alarm about the potential loss of the Amazon more than three decades ago, described the new study as “very convincing”.

“It increased my level of anxiety,” said Dr. Nobre, who was not involved in the research.

Covering more than two million square kilometers in Brazil and neighboring countries, the Amazon is the largest rainforest in the world and plays a crucial role in mitigating climate change in most years by absorbing more carbon dioxide. of the atmosphere than it releases. In its diversity of plant and animal species, it is as rich, if not more, than anywhere else on the planet. And it pumps so much moisture into the atmosphere that it can affect the weather beyond South America.

But climate change, along with widespread deforestation and burning for agriculture and ranching, has wreaked havoc on the Amazon, making it hotter and drier. The region, one of the wettest on the planet, has experienced three droughts since 2000.

Most previous studies of resilience in the Amazon relied on models, or simulations, of how forest health might change over time. In the new research, the scientists used real observations: decades of remote sensing data from satellites that measure the amount of biomass in specific areas, which correlates with their health status. Looking only at pristine parts of the rainforest, the researchers found that, overall, since 2000, these areas have lost their resilience. For example, it has taken increasingly longer for forest areas to regain their health after suffering from a drought.

“This lack of resilience shows that indeed this forest can only take a beating,” said Paulo Brando, a tropical ecologist at the University of California, Irvine, who was not involved in the study. “It reduces the ability to rebound.”

But Dr Brando said that was not necessarily a sign that a tipping point was inevitable, and stressed the need to stop clear-cutting and forest degradation in the region. “These systems are very resilient, and the fact that we have reduced the resilience does not mean that it has lost all of its resilience,” he said. “If you leave them alone for a bit, they come back very strong.”

The researchers found that more than three-quarters of intact rainforest had lost resilience during that time, and the loss was greatest in areas that were drier or closer to human activities like logging. the study was published in the journal Nature Climate Change.

Chris Boulton, a researcher at the University of Exeter and lead author of the study, said the Amazon looked like a giant water recycling network, as moisture from evaporation and transpiration trees is blown by the winds. Thus, the loss of part of the forest and part of the moisture leads to greater drought elsewhere.

“You can imagine that as the Amazon dries up, you start to see that resilience being lost faster and faster,” Dr Boulton said. Forests could then decline and die relatively quickly and become more savannah-like, with grasses and far fewer trees.

Not only would the loss of forest trees add the carbon stored in their tissues to the atmosphere, but savannas would also absorb far less carbon than the large broadleaf trees they replaced. The savannah habitat would also harbor far fewer species.

Dr Nobre said the research shows that the Amazon “is at the edge of this cliff, this shift to a different ecosystem”. And if that were to happen, he added, “it would be the new ecosystem for hundreds of years, maybe thousands of years.”

About 17 percent of the Amazon has been deforested in the past half-century, and although the pace of deforestation has slowed for a few years in Brazil, it has resumed more recentlyly. The researchers said their work shows that efforts to stop deforestation will not just protect specific areas, but will affect the resilience of the Amazon as a whole.

“They are absolutely right,” Dr. Nobre said. We have to get to zero deforestation, zero forest degradation,” adding, “We still have a chance to save the forest.”

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Newsrust - US Top News: Amazon rainforest may be approaching critical tipping point, study finds
Amazon rainforest may be approaching critical tipping point, study finds
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