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Extreme weather events threaten river ecosystems
2026-05-20
Research indicates that rivers in different regions of the planet are undergoing profound transformations that exceed their capacity for resilience.
By Michelle Braz | Agência FAPESP* – Severe droughts, intense floods, and heat waves are pushing river ecosystems beyond their natural limits of resilience. A review of data on river systems across several continents published in the journal Nature Reviews Biodiversity shows that, in most cases, nature is unable to return to its previous state after successive extreme weather events. The consequences range from local extinctions and food chain collapses to permanent changes in the services that rivers provide to human societies.
“Extreme weather events are increasing in severity and frequency, fundamentally reshaping river ecosystems. Rivers function as interconnected networks, and therefore the impacts of an extreme event are almost never restricted to a single point; they spread throughout the entire system,” warns Tadeu Siqueira, one of the authors of the article. He is a professor at the Institute of Biosciences of São Paulo State University (IB-UNESP) in Rio Claro, Brazil, and the Integration Coordinator at the Center for Research on Biodiversity Dynamics and Climate Change (CBioClima), one of FAPESP’s Research, Innovation, and Dissemination Centers (RIDCs).
One of the scenarios addressed by the study involves severe droughts that lead to the interruption of flow at river headwaters. Under these conditions, organic matter accumulates in dry areas. When water returns, large volumes of this material are carried downstream. This process can result in water deoxygenation, fish die-offs, and damage to human activities such as power generation.
So-called compound extreme events, which are combinations of droughts accompanied by heat waves or wildfires followed by heavy rains, produce disproportionate impacts and intensify the risk. Recent examples include the plankton collapse in the Yangtze River in China in 2022 and the fish die-off in the Klamath River in California after a series of fires and storms.
…
Tonkin, J.D., Siqueira, T., Merder, J. et al. Extreme events and river biodiversity under climate change. Nat. Rev. Biodivers. 2, 150–169 (2026). https://doi.org/10.1038/s44358-026-00131-7
Research indicates that rivers in different regions of the planet are undergoing profound transformations that exceed their capacity for resilience.
By Michelle Braz | Agência FAPESP* – Severe droughts, intense floods, and heat waves are pushing river ecosystems beyond their natural limits of resilience. A review of data on river systems across several continents published in the journal Nature Reviews Biodiversity shows that, in most cases, nature is unable to return to its previous state after successive extreme weather events. The consequences range from local extinctions and food chain collapses to permanent changes in the services that rivers provide to human societies.
“Extreme weather events are increasing in severity and frequency, fundamentally reshaping river ecosystems. Rivers function as interconnected networks, and therefore the impacts of an extreme event are almost never restricted to a single point; they spread throughout the entire system,” warns Tadeu Siqueira, one of the authors of the article. He is a professor at the Institute of Biosciences of São Paulo State University (IB-UNESP) in Rio Claro, Brazil, and the Integration Coordinator at the Center for Research on Biodiversity Dynamics and Climate Change (CBioClima), one of FAPESP’s Research, Innovation, and Dissemination Centers (RIDCs).
One of the scenarios addressed by the study involves severe droughts that lead to the interruption of flow at river headwaters. Under these conditions, organic matter accumulates in dry areas. When water returns, large volumes of this material are carried downstream. This process can result in water deoxygenation, fish die-offs, and damage to human activities such as power generation.
So-called compound extreme events, which are combinations of droughts accompanied by heat waves or wildfires followed by heavy rains, produce disproportionate impacts and intensify the risk. Recent examples include the plankton collapse in the Yangtze River in China in 2022 and the fish die-off in the Klamath River in California after a series of fires and storms.
…