Science Snippets: Rivers Throughout the World are Losing Oxygen Due to Climate Change

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Rivers losing oxygen might not seem like a big deal. However, just as humans and other animals need access to oxygen on land, aquatic organisms need oxygen, too.

From the Associated Press on 15 May 2026 comes a story titled Scientists find climate change is reducing oxygen in rivers worldwide. The lede refers to a peer-reviewed paper: “Global warming is causing rivers to slowly lose oxygen, threatening fish and other lives in the waterways, a new study shows.”

The next paragraph provides an overview of the peer-reviewed paper and includes an embedded link to the peer-reviewed paper: “Researchers in China used satellites and artificial intelligence to track and analyze oxygen levels in more than 21,000 rivers across the globe since 1985. They found oxygen levels have dropped an average of 2.1% since 1985, according to a study published … in Science Advances. That doesn’t seem like much but it adds up and if it continues or accelerates, rivers in the Eastern United States, India and across the tropics could lose enough oxygen by the end of the century to suffocate some fish and create dead zones, the study said.”

The next paragraph elaborates: Basic chemistry and physics dictate that warmer water holds less oxygen, scientists said. Warmer water, which happens with human-caused climate change, releases more oxygen into the atmosphere.”

The next paragraph projects into the future: “If the oxygen loss rate continues at the current pace, the world’s rivers on average will lose an additional 4% of their oxygen by the end of the century, and in some cases close to 5%, the study found. That’s when oxygen loss — called deoxygenation — becomes problematic for fish and people who rely on rivers, according to the study’s lead author Qi Guan, an environmental scientist at the Chinese Academy of Sciences in Nanjing.”

Beneath a subsection titled “More dead zones appear,” we are informed that dead zones have already occurred: “Scientists worry that oxygen levels in rivers could fall so low that dead zones appear, as they have in the Gulf of Mexico, Chesapeake Bay and Lake Erie. Those are areas where fish struggle to breathe and die.

The lead author of the peer-reviewed paper is then quoted: “Deoxygenation is a very slow process. If we have a long period, the negative impact will attack the river ecosystems. The low level of oxygen can cause a series of ecological crises such as biodiversity decline, water quality degradation and maybe some fish will die.”

The next subsection is titled, “India, Eastern US and the Amazon are hot spots.” It describes these areas and provides reasons for labeling them as dangerous areas: “Earlier this century, India’s heavily polluted Ganges River was losing oxygen more than 20 times faster than the global average ... Even with moderate-to-high increases in global carbon dioxide emission rates — not the implausible worst-case scenario — rivers in the Eastern United States, the Arctic, India and much of South America are projected to lose about 10% of their oxygen by the end of the century, the analysis showed.”

The peer-reviewed study “found several reasons for oxygen loss in the world’s rivers, including nutrient pollution from fertilizer and urban runoff, along with dam construction, flow and wind issues. But nearly 63% of the problem is from warmer water, the study found.

A Duke University ecologist and biogeochemist who was not part of the peer-reviewed study mentioned in this article said, “as rivers warm it becomes easier and easier for the same pollution problems as before to cause more severe, more long lasting or more widespread hypoxia and anoxia.” Anoxia is the total loss of oxygen.

I now turn to the peer-reviewed paper in the renowned Science Advances. Titled Sustained deoxygenation in global flowing waters under climate warming, the paper was written by three scholars and published 15 May 2026. The Abstract provides an excellent overview of the research and its findings: “Dissolved oxygen …, as a vital material sustaining aquatic ecosystems, has declined markedly in oceans, lakes, and coastal waters, yet unbiased understandings of changing dissolved oxygen concentrations in each individual river segment globally remain a challenge. Here, we estimate dissolved oxygen … concentrations in 21,439 rivers globally between 1985 and 2023, based on Landsat observations and climatic data, and examine their patterns and trends. We find sustained deoxygenation in global rivers, at a rate of −0.045 mg liter⁻¹ decade⁻¹, with 78.8% experiencing fluvial deoxygenation, driven mainly by oxygen solubility and temperature. Moreover, short-term heatwaves and dam impoundment exert non-neglecting influence on these changes. Future projections demonstrate that global fluvial dissolved oxygen … concentrations decline by 1.1% ± 1.6% under SSP1–2.6 and 4.7% ± 2.7% under SSP5–8.5 throughout the 21st century. Our study provides an unbiased baseline for escalating deoxygenation in global fluvial ecosystems that underscores targeted measures to mitigate deoxygenation threats and protect ecosystem health.”

The first paragraph of the Introduction of the peer-reviewed paper cites many other peer-reviewed sources in briefly providing an overview of the situation and why it matters: “The concentration of dissolved oxygen … is fundamental to fluvial ecosystem health and services, as it can sustain ecosystem functioning, regulate biogeochemical cycle, protect aquatic biodiversity, and measure drinking water quality. Fluvial dissolved oxygen … concentrations generally depend on covarying physical, biological, and chemical processes that encompass atmospheric oxygen dissolution, ecosystem metabolism, and microbial decomposition. Oxygen dissolution, defined by oxygen solubility, depends on water temperature, air pressure, and salinity. As temperature increases, … oxygen solubility will decline and thus accelerate deoxygenation. Ecosystem metabolism (photosynthesis and respiration that sustain fluvial ecosystems) varies with multi-drivers, such as temperature, light and flow regimes, land use, and nutrients. In photosynthesis-dominated rivers, aquatic vegetation and phytoplankton can produce oxygen to enhance dissolved oxygen … levels and even supersaturate dissolved oxygen … in surface waters. Conversely, when respiration exceeds photosynthesis, fluvial ecosystems will consume oxygen and be vulnerable to hypoxia …, which severely threatens well-oxygenated habitats and survival conditions for aquatic species and organisms. Moreover, microbial decomposition, as an oxygen-consuming process, can rapidly deplete oxygen and thereby form anoxic conditions, named as dead zones …, when massive phytoplankton biomass decays, leading to mass fish kills, water quality degradation, and ecosystem service loss. However, little is known about how these processes regulate fluvial dissolved oxygen … concentrations on a global basis.”

At this point, you probably recognize that the oxygen content of waterways is critically important to organisms in waterways. And, because we are one, you undoubtedly realize the importance of organisms in the places you spend little time.