Study Finds Rivers Worldwide Losing Oxygen Due to Warming

Oxygen levels in rivers across the globe have declined an average of 2.1 percent since 1985, according to a study published Friday in Science Advances. Researchers in China analyzed data from satellites and artificial intelligence covering more than 21,000 rivers.

The study determined that warmer water from climate change accounted for nearly 63 percent of the oxygen loss. Basic chemistry shows that warmer water holds less dissolved oxygen and releases more of it into the atmosphere. If the current rate of loss continues, the world's rivers would lose an additional 4 percent of their oxygen by the end of the century on average, and close to 5 percent in some locations.

The study's lead author stated that this level of deoxygenation becomes problematic for fish and for people who rely on rivers. Rivers in the Eastern United States, India, the Arctic and much of South America are projected to lose about 10 percent of their oxygen by 2100 under moderate-to-high carbon dioxide emission increases.

India's Ganges River was losing oxygen more than 20 times faster than the global average earlier this century. Tropical rivers such as the Amazon are also identified as areas of concern.

The study warns that continued oxygen loss could create more dead zones where fish struggle to breathe. Such zones have already appeared in the Gulf of Mexico, Chesapeake Bay and Lake Erie. The number of days with dead zone conditions in the Amazon has increased by nearly 16 days per decade since 1980, according to a separate study cited in the report.