Data analysis

New evidence from analysis of satellite data

The Amazon rainforest is likely losing its resilience, suggests analysis of data from high-resolution satellite images. This is due to stress resulting from a combination of logging and burning – the influence of human-induced climate change is not clearly determinable so far, but is likely to be of great importance in the future. For about three-quarters of the forest, the ability to recover from a disturbance has been declining since the early 2000s, which scientists see as a wake-up call. The new evidence is derived from advanced statistical analysis of satellite data on changes in vegetation biomass and productivity.

“Reduced resilience – the ability to recover from disturbances such as droughts or fires – can mean an increased risk of Amazon rainforest dieback. The fact that we are seeing such a loss of resilience in observations is concerning,” says Niklas Boers of the Potsdam Institute for Climate Impact Research and the Technical University of Munich, who conducted the study together with researchers from the University of Exeter, UK.

“The Amazon rainforest is home to unique biodiversity, strongly influences rainfall throughout South America through its enormous evapotranspiration, and stores huge amounts of carbon that could be released as greenhouse gases if even dieback occurs. partial, in turn contributing to global warming,” explains Boers. “That’s why the rainforest is of global importance.”

“When the tilt itself is observable, it will be too late”

The Amazon is considered a potential tipping point in the Earth system and a number of studies have revealed its vulnerability. “However, computer simulation studies of its future yield a range of results,” Boers says. “We therefore looked at specific observational data to detect signs of changing resilience over the past decades. observable, it would probably be too late to stop it.” The research is part of the Tipping Points in the Earth System (TiPES) project funded by the European Union’s Horizon 2020 programme.

The team from the Potsdam Institute for Climate Impact Research and the Global Systems Institute at the University of Exeter used stability indicators that had previously been applied to the Greenland Ice Sheet and the Atlantic overturning circulation. These statistical indicators aim to predict a system’s approach to abrupt change by identifying a critical slowdown in the system’s dynamics, for example its response to climate variability. Analysis of two sets of satellite data, representing forest biomass and greenness, revealed the critical slowdown. This critical slowdown can be seen as a weakening of the restoring forces that usually bring the system back to its equilibrium after disturbances.

“A system may seem stable if we only consider its average state”

While a system may appear stable if only its average state is considered, closer examination of the data with innovative statistical methods may reveal loss of resilience,” says Chris Boulton of the Global Systems Institute at the University of ‘Exeter. the simulations indicated that large parts of the Amazon may be doomed to dieback before showing a strong change in average state. Our observational analysis now shows that in many areas destabilization does indeed appear to be already underway.”

To try to determine the causes of the loss of resilience that the scientists find in the data, they explored the relationship with rainfall in a given area of ​​the Amazon, resulting in three “once in a century” drought episodes in the region. The drier areas are more at risk than the wetter ones. “This is alarming, as IPCC models predict general drying of the Amazon region in response to anthropogenic global warming,” Boers says. Another factor is the distance of an area from roads and settlements from where people can access the forest. The data confirms that areas close to human land use are more at risk.

“Our new analysis of empirical data provides further evidence for concerns about forest resilience, particularly in the near future,” said Tim Lenton, director of the Global Systems Institute. “This confirms that strongly limiting logging, but also limiting global greenhouse gas emissions, is necessary to safeguard the Amazon.”