Where in the Amazon region could nature best defy the increased droughts caused by climate change? In the depressions of the lowlands, a study now clarifies. Evaluations of satellite data show that moisturizing fog can still linger there even when it is dry. The identified foggy valleys are therefore refuges for the biodiversity of the Amazon region that are particularly worthy of protection. In addition, the targeted preservation of these areas could help curb feedback effects that further exacerbate climate change, the scientists say.
Natural wonder of global importance: The Amazon region is a biodiversity hotspot in the world, has a far-reaching influence on the weather and, thanks to its enormous biomass production, also binds a large amount of climate-damaging greenhouse gases. But the lush and influential living environment is threatened: In addition to deforestation, climate change is causing a lack of the element that gives the rainforest its name: unusually little rainfall is making the ecosystem increasingly difficult to cope with. Such periods of drought occurred particularly in 2005 and 2010, and in 2015/16 too little rain fell everywhere in Amazonia.
Satellite views of wafts of fog
In addition, it has already been shown that forest damage further intensifies this development: "Since part of the precipitation is generated by the evaporation of the forest itself, the combination of climate change and forest destruction threatens a self-reinforcing downward spiral," says senior author Jörg Bendix from the Philipps University marburg Ultimately, the balancing function of the Amazon region in the context of climate change is also threatened. The best possible protection of the region is therefore of great importance. In turn, certain areas could be particularly important, which can serve as refuges in times of stress and thus as centers for the subsequent recovery of the ecosystem.
As Bendix and his colleagues explain, fog can provide wet retreats in forests when the climate warms and rains fail. Because these "low-level clouds" can provide a twilight, cool and humid environment that enables the sensitive plants and thus other living beings to survive. "Until now, however, it was unclear where this water source occurs particularly frequently and whether it will prove to be resistant to increasing drought in climate change," says co-author Lukas Lehnert from the Ludwig Maximilians University in Munich. In order to close this research gap, the scientists evaluated long-term satellite data that depict the weather in the Amazon region in detail.
Humid refuges in lowland valleys
First of all, the results made it clear how strongly the lowland areas of the Amazon region are usually characterized by fog. "We then took a close look at the drought phases of the past 18 years," says lead author Marius Pohl from the Philipps University of Marburg. During these periods, the fog disappeared widely, the data showed. However, certain areas were significantly less affected: "It turned out that fog still occurs frequently, particularly in the valleys of the Amazon basin," says Pohl. There, the moisturizing swaths proved to be particularly resistant to the droughts. "We find that these refugia are found throughout the Amazon Basin, with the highest abundance and most stable in river valley areas," the scientists write.
According to them, a clear message emerges from the findings: Based on their results, the authors strongly recommend protecting the wet retreat areas from deforestation and other pressures, especially in areas that are highly threatened by drought. "The targeted protection of these refuges could help to preserve the biological diversity and the functioning of the Amazon ecosystem in the face of future droughts as a result of climate change. This would also help stabilize atmospheric moisture recycling and make the region more resilient to climate change," the authors write. Ultimately, protecting the Misty Valleys could also help preserve the rainforest's broader function as a bulwark against climate change.
Source: University of Marburg, specialist article: Communications Earth & Environment, doi: 10.1038/s43247-023-00867-6