Earth's oceans rapidly losing oxygen, scientists warn

A new scientific analysis warns that Earth's oceans are losing oxygen at an accelerating rate, a trend that researchers say could destabilize the planet's life-support systems. The study, published by an international team of scientists, finds that oxygen levels in the world's oceans have dropped by roughly 2% over the past 50 years, with the rate of loss increasing in recent decades. This deoxygenation is driven primarily by climate change, as warmer waters hold less dissolved oxygen, and by nutrient pollution from agriculture and sewage, which fuels algal blooms that consume oxygen when they decompose.

The phenomenon affects marine ecosystems globally, from coastal zones to the deep sea. Fish, crabs, and other marine animals that depend on oxygen are being forced to migrate to shallower or cooler waters, disrupting food webs and fisheries that billions of people rely on for protein. The researchers note that oxygen-depleted "dead zones" have expanded from about 45 known sites in the 1960s to over 700 today, covering a total area roughly the size of the European Union. These zones can cause mass die-offs of marine life and release harmful greenhouse gases like nitrous oxide.

Why this matters, the scientists argue, is that ocean oxygen loss is pushing Earth toward a planetary boundary that could trigger irreversible changes. The study, published in the journal Nature, identifies deoxygenation as a key indicator that the planet is entering "unsafe" territory, alongside other global threats like climate change and biodiversity loss. The authors warn that if current trends continue, large parts of the ocean could become uninhabitable for many species by the end of the century.

The research builds on decades of ocean monitoring data from ships, buoys, and satellites. It highlights that oxygen loss is most severe in the Pacific Ocean, but all ocean basins are affected. The scientists call for urgent reductions in greenhouse gas emissions and nutrient pollution to slow the decline. They also recommend expanding marine protected areas and improving wastewater treatment to help coastal waters recover. Without such action, they caution, the ocean's ability to support life—and to regulate Earth's climate—will be severely compromised.