Science Snippets: Human Activities Cause Inland Waters to Become Oxygen Sinks

Draft script:

Inland waters are important. Lakes, reservoirs, rivers, and streams are critical parts of the oxygen budget on Earth. Not surprisingly, human activities have disrupted the processes by which oxygen is retained in inland waters. The collective effects of more than eight billion people are tremendous.

From Phys.Org on 4 April 2025 comes an article titled Oxygen is running low in inland waters – and human activities are to blame. Here’s the lede, plus five additional sentences to complete the first paragraph: “Rivers, streams, lakes, and reservoirs aren’t just scenic parts of our landscape—they’re also vital engines for life on Earth. These inland waters “breathe” oxygen, just like we do. But a new study led by Utrecht University researchers shows that we’ve been suffocating them during the last century, an era also known as the Anthropocene. The research, published today in Science Advances, reveals that the way oxygen is produced and used in inland waters has dramatically changed since 1900. The culprit? Human activities.”

The magnitude of the crisis is revealed in the following paragraph: “Oxygen, the most critical resource for life on Earth, plays an important role in other nutrient cycles such as carbon and nitrogen. Oxygen depletion in water, called hypoxia, is causing problems. They are piling up in various coastal and freshwater systems. The result? Dying fish, disrupted food webs, poor water quality and more which are already affecting freshwater ecosystems across the globe. This study shows it’s not just a local problem—it’s a planetary one.”

In other words, we have yet another planetary disaster created by the mass of humans. More than eight billion humans chasing more, more, and more on a finite planet has disrupted Earth’s oxygen cycle. As I pointed out via blog post on 28 May 2009, “If you think the economy is more important than the environment, try holding your breath while counting your money.” Three minutes into this activity, give-or-take a minute, air becomes limiting to your continued existence.

The bottom line comes in the final two paragraphs at the Phys.Org article: “This study showed that the modern oxygen cycle in inland waters looks nothing as it did in the early 1900s.” One of the authors of the attendant peer-reviewed paper is quoted: “Even though these waters cover just a tiny fraction of Earth’s surface, they now remove nearly 1 billion [metric] tonnes of oxygen from the atmosphere each year—overall half of what the entire ocean emits back.”

The lead author of the peer-reviewed paper is then quoted: “We can’t ignore inland waters in global climate and oxygen budgets anymore. They’re changing faster than we thought, and they’re crucial pieces of the Earth system puzzle.”

The peer-reviewed, open-access paper was published in the renowned Science series. Published on 4 April 2026 in Science Advances, the paper is titled Global inland-water oxygen cycle has changes in the Anthropocene. Created by eight scholars, the Abstract provides an excellent overview of the research and its findings: “Inland waters are an important resource, a highly diverse habitat, and a key component of global biogeochemical cycles. Oxygen plays a major role in inland-water ecosystem functioning, but long-term changes in its cycling remain unknown. Here, we quantify global inland-water oxygen production, consumption, and exchange with the atmosphere during 1900–2010 using a spatially explicit, mass-balanced, mechanistic model that takes into account changes in climate, hydrology, human activities, and the coupled biogeochemical (oxygen-nutrient-organic matter) dynamics. The model results show that global inland-water oxygen turnover increased during 1900–2010: production from 0.16 to 0.94 Petagrams year⁻¹ and consumption from 0.44 to 1.47 Petagrams year⁻¹. Inland waters overall remained heterotrophic and a sink of atmospheric oxygen. Direct human perturbations (changes in hydrology and nutrient supply) were more important in increasing oxygen turnover than indirect effects via warming.” As I have pointed out previously in this space, a Petagram is equal to one gigaton, or 10¹⁵ grams. The numbers mentioned in the Abstract represent huge changes in oxygen turnover.

That final sentence is a surprise, at least to me: “Direct human perturbations (changes in hydrology and nutrient supply) were more important in increasing oxygen turnover than indirect effects via warming.” We are warming the planet at a rate unprecedented in planetary history. Yet, “direct human perturbations … were more important in increasing oxygen turnover than indirect effects via warming.”

The collective power of more than eight billion humans is on display yet again. And, yet again, we are using our power unwisely. When will it end? With us, I suppose.