Heatwaves and Droughts Are Shaking River Ecosystems

Chim Sâu

26-03-2025 

“As time passes, news about the now hotter Earth buzzes through the bird village. Those kingfishers residing along the banks of the Red River often report drying riverbeds and skinny fish. As Kingfisher casts his gaze upon the events that have unfolded, he can’t help but feel a sense of unease creeping up within him.”

In “GHG Emissions”; Wild Wise Weird [1]

As climate extremes intensify, rivers—critical conduits for global carbon and nutrient cycles—are increasingly vulnerable. A new study by Lyu et al. [1] reveals how a record-breaking drought-heatwave event in the summer of 2022 dramatically disrupted aquatic plankton communities in China’s Yangtze River, threatening biodiversity, stability, and carbon balance.

Using environmental DNA (eDNA) techniques, researchers assessed six major planktonic groups across normal and extreme hydrological periods. During the extreme event, alpha diversity (local species richness) plummeted, while beta diversity (differences between regions) rose sharply. These shifts indicate both a loss of species and a fragmentation of ecological function—warning signs of declining ecosystem resilience [2].

Perhaps most striking was the shift in algal communities. Diatoms (Bacillariophyta), efficient carbon-fixers and key to food web stability, were largely replaced by Cyanobacteria—organisms favored by warm, stagnant waters and often produce toxins that harm aquatic life [3]. This transition, coupled with an elevenfold increase in algal gene abundance, correlated with elevated levels of labile organic carbon, suggesting reduced potential for long-term carbon storage.

Water temperature, a dominant environmental driver, rose significantly during the event. While animal plankton showed resilience—likely due to physiological adaptability—microbial communities were more severely affected, underlining the vulnerability of lower trophic levels to climatic stress.

These findings underscore the growing threat of compound drought-heatwave events, which are projected to become ten times more frequent under high-emission scenarios. The ecological shifts observed in the Yangtze River may foreshadow similar disruptions globally, especially in higher-latitude regions facing even greater temperature increases, which may require a high Nature Quotient approach to comprehend [4].

Protecting riverine ecosystems requires urgent climate action and adaptive water management strategies to buffer against the mounting impacts of extreme weather [5].

References

[1] Vuong QH. (2024). Wild Wise Weird. https://www.amazon.com/dp/B0BG2NNHY6/ 

[2] Lyu J, et al. (2025). Extreme drought-heatwave events threaten the biodiversity and stability of aquatic plankton communities in the Yangtze River ecosystems. Communications Earth & Environment, 6, 171. https://www.nature.com/articles/s43247-025-02143-1 

[3] Cardinale BJ, et al. (2012). Biodiversity loss and its impact on humanity. Nature, 486, 59-67. https://www.nature.com/articles/nature11148 

[4] Paerl HW, Huisman J. (2009). Climate change: a catalyst for global expansion of harmful cyanobacterial blooms. Environmental Microbiology Reports, 1(1), 27-37 (2009). https://doi.org/10.1111/j.1758-2229.2008.00004.x 

[5] Nguyen MH. (2024). How can satirical fables offer us a vision for sustainability? Visions for Sustainability. https://ojs.unito.it/index.php/visions/article/view/11267