Planetary boundaries represent thresholds in major Earth system processes that are sensitive to human activity and control global-scale habitability and stability. These processes are interconnected such that movement of one planetary boundary process can alter the likelihood of crossing other boundaries. Here we argue that the observed deoxygenation of the Earth’s freshwater and marine ecosystems represents an additional planetary boundary process that is critical to the integrity of Earth’s ecological and social systems, and both regulates and responds to ongoing changes in other planetary boundary processes. Research on the rapid and ongoing deoxygenation of Earth’s aquatic habitats indicates that relevant, critical oxygen thresholds are being approached at rates comparable to other planetary boundary processes. Concerted global monitoring, research and policy efforts are needed to address the challenges brought on by rapid deoxygenation, and the expansion of the planetary boundaries framework to include deoxygenation as a boundary helps to focus those efforts.

行星边界代表了主要地球系统过程的阈值，这些过程对人类活动敏感并控制着全球范围的宜居性和稳定性。这些过程是相互关联的，因此一个行星边界过程的运动可以改变跨越其他边界的可能性。在这里，我们认为，观察到的地球淡水和海洋生态系统的脱氧代表了一个额外的行星边界过程，它对地球生态和社会系统的完整性至关重要，并且调节和响应其他行星边界过程的持续变化。对地球水生栖息地快速持续脱氧的研究表明，相关的临界氧气阈值正在以与其他行星边界过程相当的速度接近。需要协调一致的全球监测、研究和政策努力来应对快速脱氧带来的挑战，而扩大行星边界框架以将脱氧纳入边界有助于集中这些努力。