“This study is designed to elevate the profile of aquatic deoxygenation as a global threat and show that it does not operate in isolation.” Human-caused warming, excess nutrient pollution and changes in the circulation that carries oxygen into deeper waters are the primary drivers of aquatic deoxygenation. Marine mammals can also be affected despite breathing at the surface because oxygen loss changes their habitats, prey, and surrounding food webs. They hope the work encourages researchers and policymakers to address aquatic deoxygenation together with the other pressures affecting Earth’s systems. “Adding aquatic deoxygenation to the Planetary Boundaries framework will help us understand its impacts on Earth system stability,” said Ferrer.