Global River Oxygen Levels Dropping as Climate Change Intensifies

Global Decline in Dissolved Oxygen

Nearly 80% of river systems worldwide have been steadily losing dissolved oxygen over the last 40 years. According to a sweeping global analysis of more than 21,000 waterways, climate change has emerged as the primary driver behind this trend.

Scientists describe the phenomenon as a "silent crisis," noting that rivers are quietly running out of oxygen as global temperatures rise and heatwaves intensify. The depletion of dissolved oxygen is critical for the survival of aquatic ecosystems, as fish and other river-dwelling organisms rely on these levels to breathe.

Tropical Vulnerability

Contrary to previous scientific expectations, the most oxygen-depleted systems are located in the tropics rather than the Arctic. Researchers had long assumed that high-latitude rivers in regions such as Siberia, northern Canada, and Scandinavia faced the greatest risk because these areas are climate change hotspots.

However, the study found that tropical rivers are especially vulnerable to dangerous low-oxygen conditions. This is attributed to the fact that tropical waters were already warmer and possessed lower levels of dissolved oxygen from the start, leaving them with less of a buffer as temperatures continue to climb.

Regional Impacts and the Ganges River

While the decline is a global trend, certain river systems are experiencing the crisis at an accelerated pace. The Ganges River, in particular, is losing oxygen 20 times faster than the global average.

This rapid deoxygenation in specific basins highlights the uneven distribution of the crisis, though the overall trend remains consistent across the majority of the 21,000 systems analyzed.