I wish that the only issue were the "decline of the Empire". I would then sleep much easier at night. Actually, I'd be ecstatic!
Alarmingly, the pH drop observed so far and the predicted trajectory under current emissions trends are 100 times faster than any changes in prior millennia. Left unchecked, CO2 levels will create a very different ocean, one never experienced by modern species. Adaptation is even more unlikely because the effects of acidification, and the other struggles creatures face, interact. For example, increased CO2 levels can narrow the temperature range in which an individual can survive. We already see such constraints on corals and some algae, which become heat-stressed at lower temperatures than normal if exposed to higher CO2.