Why is ocean acidification a major political issue?

Ocean acidification, caused by the absorption of carbon dioxide emitted by human activities, is one of the most worrying challenges of climate change. It threatens marine ecosystems, in particular coral reefs, and exacerbates inequalities, particularly affecting countries dependent on marine resources. This article presents the mechanisms of ocean acidification, its ecological, economic and social impacts, and identifies levers for action at different scales. It stresses the urgent need to rapidly reduce global CO₂ emissions in order to maintain the average ocean pH above the critical threshold for the survival of marine ecosystems. Finally, it calls for greater political mobilization, appropriate funding, and increased international cooperation, particularly ahead of the United Nations Ocean Summit (UNOC3, June 2025).