Global warming is gradually reducing oxygen levels in rivers, posing a threat to aquatic life. A study by Chinese researchers utilized satellites and artificial intelligence to track oxygen levels in over 21,000 global rivers. Since 1985, these levels have dropped by an average of 2.1%, according to research published in Science Advances.
Even a small decrease in oxygen can accumulate to significant levels. If the current trend continues, rivers in regions such as the Eastern United States, India, and tropical areas might lose enough oxygen by the century’s end to become uninhabitable for some fish, creating dead zones.
Causes of Oxygen Loss
Warmer water, a result of human-caused climate change, holds less oxygen and releases more into the atmosphere. The study predicts that if oxygen loss persists, the average world’s rivers will lose up to an additional 5% of their oxygen by the end of the century.
Lead author Qi Guan from the Chinese Academy of Sciences expresses concern about the potential ecological crises from low oxygen levels, including biodiversity decline and water quality degradation.
Increase in Dead Zones
Scientists warn that reduced oxygen may lead to more dead zones in rivers, similar to those in the Gulf of Mexico, Chesapeake Bay, and Lake Erie. Karl Flessa from the University of Arizona notes that such conditions can result in unpleasant-smelling, life-devoid areas, particularly during heatwaves.
Regional Hot Spots
Regions like India’s Ganges River previously suffered from oxygen loss at rates over 20 times the global average. The study forecasts that rivers in places like the Eastern United States and the Amazon could lose about 10% of their oxygen by the century’s conclusion.
Hydrology expert Marc Bierkens reported last year that oxygen stress in rivers increased significantly, with more frequent dead zone occurrences due to ongoing warming.
Factors Contributing to Deoxygenation
Factors responsible for oxygen reduction include nutrient pollution, urban runoff, and dam construction. However, 63% of the decline is attributed to rising water temperatures.
Emily Bernhardt, a Duke University ecologist, emphasizes that warming rivers exacerbate existing pollution issues, making hypoxia and anoxia more severe.
Addressing water pollution is increasingly critical as river temperatures rise, presenting further challenges in maintaining river health.