Oxygen is a vital element for virtually all animals on Earth and many microbes. But oxygen concentrations are falling in some of the most valuable ecosystems on the planet. According to a recent paper, the number of freshwater and coastal water bodies with little to no oxygen has increased in coastal areas, with hundreds of regions affected worldwide. Meanwhile, in the open ocean, oxygen-deficient waters have increased fourfold since 1960.
In the new paper, published in Nature Ecology & Evolution, researchers around the globe are urging leaders to acknowledge the ocean’s oxygen loss as a new “planetary boundary.” Planetary boundaries are global thresholds for major Earth systems, beyond which humanity cannot safely operate. The nine existing boundaries include climate change and freshwater. In this Q&A, we spoke with co-author Denise Breitburg, a scientist emerita at the Smithsonian Environmental Research Center, on why ocean oxygen should become the 10th planetary boundary. Edited for brevity and clarity.