Swathes of the Amazon face pressures that could lead to a “tipping point” by 2050, prompting large-scale collapse of the key forest systems, scientists have warned.
A study published in the journal Nature found that by mid-century 10%-47% of Amazonian forests will be threatened by a combination of impacts including global warming, changing rainfall, longer dry seasons, deforestation and fires.
That could trigger the collapse of forest ecosystems, potentially driving further climate change, causing irreversible loss of wildlife, affecting rainfall across the region and South America, and hitting lives, cultures and livelihoods, the paper said.
The Amazon rainforest holds more than 10% of Earth’s land-based wildlife, stores an amount of carbon equivalent to 15 to 20 years of global emissions from human activity, and has a cooling effect that helps stabilise the climate.
But the resilience of the region’s forests has been decreasing since the early 2000s, the study warned.
The research, by scientists in Brazil and around the world, looked at causes of water stress in the Amazon that is putting pressure on the forests, using natural records from across 65 million years, climate models and data such as satellite images of forest fire spread and deforestation since the 1980s.
The Amazon is threatened by rising temperatures, an increase in the number of consecutive dry days, and changes to rainfall patterns that are making some areas much drier and others wetter, it said.
As much as 38% of the remaining Amazon forest has been degraded by logging, fires under the canopy, and repeated extreme drought, while road networks are pushing the damage throughout the core of the ecosystem, the study said.
By 2050, 10%-47% of the area will be exposed to a combination of threats that may trigger a shift from natural forest to different landscapes such as savanna and degraded forests or other areas with low tree cover.
This could threaten the Amazon’s role as a carbon store or “sink”, make local climate change impacts worse, and affect the 40 million people who live there, including indigenous people and local communities, the study said.
Potsdam Institute for Climate Impact Research (PIK) scientist Boris Sakschewski, one of the authors of the study, said: “The south-eastern Amazon has already shifted from a carbon sink to a source – meaning that the current amount of human pressure is too high for the region to maintain its status as a rainforest over the long term.
“But the problem doesn’t stop there. Since rainforests enrich the air with a lot of moisture which forms the basis of precipitation in the west and south of the continent, losing forest in one place can lead to losing forest in another in a self-propelling feedback loop or simply ‘tipping’.”
The researchers suggested safe boundaries for each of the critical drivers behind the threats – for example, calling for global warming to be limited to 1.5C above pre-industrial levels in line with international agreements.
They also said deforestation should be limited to 10% of the original Amazon forest cover, which requires ending large-scale deforestation and restoring at least 5% of the region, which has already seen as much as 15% of its forests lost.
Co-author Niklas Boers, from PIK and professor of Earth system modelling at the Technical University of Munich, said: “To maintain the Amazon forest within safe boundaries, local and global efforts must be combined.
“Deforestation and forest degradation have to end and restoration has to expand.
“Moreover, much more needs to be done to stop greenhouse gas emissions worldwide.”