Climate warming driving oxygen loss in global rivers: study

A new study has found that climate warming is causing a widespread and persistent decline in oxygen levels in rivers worldwide, posing serious risks to freshwater ecosystems.

Published in the journal Science Advances, the research was led by scientists from the Nanjing Institute of Geography and Limnology under the Chinese Academy of Sciences.

The team analysed nearly 40 years of data from over 21,000 river stretches globally, using advanced machine learning to track oxygen changes between 1985 and 2023. On average, oxygen levels declined by 0.045 milligrams per litre per decade, with almost 80 percent of rivers showing deoxygenation.

Tropical rivers, located between 20 degrees south and north, were found to be most affected, contrary to earlier expectations. These rivers already have lower oxygen levels and are losing oxygen faster, increasing the risk of extreme low-oxygen events that can harm aquatic life.

The study attributed about 63 percent of oxygen loss to reduced solubility in warmer water, while ecosystem changes accounted for 12 percent. Heatwaves contributed nearly 23 percent, accelerating oxygen decline.

Researchers warned of threats to biodiversity and urged urgent policy action, particularly in tropical regions.