Study: Climate change is suffocating rivers worldwide

(CN) — As the universal presence of climate change-induced droughts, shrinking glaciers and extreme weather events continues, researchers have discovered another alarming effect caused by the ever-rising temperatures: the deoxygenation of rivers across the globe.

Published Friday in Science Advances, two researchers from the Chinese Academy of Sciences’ Nanjing Institute of Geography and Limnology examined satellite and climate data compiled over 38 years — from 1985 to 2023 — from 21,439 rivers around the globe. The pair used surface air temperature to identify atmospheric heatwaves and assess how short-term heat events affect dissolved oxygen levels in rivers worldwide, since comprehensive time-series water-temperature data are not available globally.

Findings showed that dissolved oxygen concentration in the rivers studied has declined by 0.045 milligrams per liter per decade, a decline that researcher Qi Guan emphasized directly connects to the deoxygenation driven by Earth’s continued warming, oxygen solubility and short-term heatwaves. Various geographic regions in India and the eastern United States appeared to experience the most drastic results compared to other areas.

An increase in algal blooms, which are excessive amounts of algae or cyanobacteria that rapidly accumulate in freshwater and aquatic environments, is also likely to be a contributing factor to dissolved oxygen, according to the researchers. Some of these algal blooms can produce toxins that damage ecosystems.

Additionally, the researchers theorized that dam construction and impoundment could contribute to deoxygenation by disrupting sediment transport and examined data from over 400 dams, distributed sporadically across the globe, with a particular focus on those in Asia and North and South America. The pair divided the study period into two sub-periods, before and after dam construction, and compared changes in fluvial — processes and environments associated with rivers — deoxygenation concentrations to measure the dam’s effects on global rivers.

Although previous studies have measured dissolved oxygen levels at regional scales, the researchers noted the pressing need for a deeper understanding of how deoxygenation in rivers and other water bodies is unfolding worldwide.

“It is imperative to formulate and implement targeted measures and strategies to mitigate river deoxygenation risks and prevent concomitant ecological disasters worldwide,” Guan and co-author Kun Shi said in a press release.

According to Guan and Shi’s estimates, global river deoxygenation rates will continue to increase throughout the rest of the 21st century, at around 1.1% under “sustainable action” and around 4.7% under “business-as-usual” scenarios.