Large parts of the Amazon region are already suffering from water stress caused by climate change and from deforestation by humans, and the trend is increasing. The ecosystem could therefore reach a tipping point much earlier than expected, from which the rainforest changes irreversibly, as researchers report in “Nature”. This would not only increase the effects of global warming locally, but would also have consequences for the climate worldwide. The scientists therefore warn that the rainforest should be better protected.
The Amazon rainforest is home to over 40 million people and a good ten percent of all species on earth. This makes it an important habitat for global biodiversity. In addition, the trees there have stored enormous amounts of carbon from the atmosphere. If all the trees there died and released this CO2 again, that would be equivalent to 15 to 20 years of human emissions. The bottom line is that the Amazon rainforest, as a carbon sink, cools the earth and makes a significant contribution to stabilizing the climate. But how long the rainforest can continue to fulfill this task is questionable. Because climate change is affecting the ecosystem, droughts and water stress are becoming more and more common. If this pressure continues to increase, scientists have long warned that the rainforest will one day reach a tipping point and collapse under the stress. However, so far they have assumed that this will no longer happen this century.
What is the status of the Amazon rainforest?
A research team led by Bernardo Flores from the Federal University of Santa Catarina in Brazil has now examined in more detail how endangered the Amazon rainforest is and when a critical point would be reached. To do this, the researchers evaluated geological climate data from the region, which cover a period of around 65 million years. They compared this data with climate models and satellite data since the 1980s and analyzed, among other things, how much forest fires and deforestation have changed the tree population in the Amazon. In total, Flores and his colleagues examined five parameters that influence the development of the rainforest: deforestation, global warming, annual rainfall, seasonal rainfall and the length of the dry season.
The analyzes showed that the Amazon rainforest could reach a climatic tipping point and change irreversibly not after 2100, but as early as 2050. At this point, between ten and 47 percent of the forest area will probably suffer from water shortage and environmental stress, the researchers predict. As a result, the ecosystem could collapse partially or completely and numerous species could become extinct. The rainforest would transform into forest or savannah and would then lose its effectiveness as a carbon sink, according to the study. This would lead to high emissions. The effects of climate change that are already noticeable could then be further intensified, particularly locally, but also around the world.
Whether the tipping point is exceeded depends on further deforestation, but also on local weather and global climate. For example, the dry season should not last longer than five months, at least 1,800 millimeters of water would have to fall annually and the earth should not warm up by more than 1.5 degrees compared to pre-industrial levels in order not to endanger the Amazon rainforest . Overall, these factors work together and reinforce each other, according to Flores and his colleagues.
Scientists call for protection of the Amazon forest
The scientists conclude that more precautionary measures need to be taken to protect the Amazon and make it more resilient. To achieve this, the deforestation of the rainforest must stop locally and areas that have already been destroyed must be restored, so that a maximum of ten percent of the original Amazon region remains deforested. In addition, a global move away from greenhouse gases in energy supply is necessary.
Source: Bernardo Flores (Federal University of Santa Catarina) et al., Nature, doi: 10.1038/s41586-023-06970-0