Rising ocean acidity from CO2 absorption is causing measurable harm to marine animals across species groups.
Ocean acidification causes welfare harm through multiple mechanisms: shell formation failure in molluscs, coral bleaching that destroys habitat and food webs, and neurological disruption in fish that impairs predator avoidance and social behaviour. Fish showing impaired predator avoidance in acidified water face increased predation stress and mortality. The scale is global and the mechanism — atmospheric CO2 — is driven by human fossil fuel use. Climate action is, ultimately, the most significant animal welfare intervention available.