FIGURE 1.1 Estimated past, present, and future ocean pH (seawater scale). In panel A, past ocean pH was calculated from boron isotopes (see Box 2.2) in planktonic foraminifera shells (Hönisch et al., 2009, blue circles) and from ice core records of pCO2, where alkalinity, salinity, and nutrients were assumed to remain constant (Petit et al., 1999, red circles). In panel B, the scale of the x-axis has been expanded to illustrate the pH trend projected over the next century. Future pH values (average for ocean surface waters) were calculated by assuming equilibrium with atmospheric pCO2 levels and constant alkalinity. Future pCO2 (atm) levels were assumed to follow the IS92 business-as-usual CO2 emissions scenario.


It may seem that ocean acidification is a concern for the future. But ocean acidification is occurring now, and the urgent need for decision support is already quite evident. Recently, failures in oyster hatcheries in Oregon and Washington have been blamed on ocean acidification, and costly treatment systems have been installed, despite the fact that the evidence linking the failures to acidification is largely anecdotal (Welch, 2009). On the other hand, there is quite convincing evidence that coral reefs will be affected by acidification (see Chapter 4), but coral reef managers, who are just now beginning to develop adaptation plans to deal with climate change, have limited information on how to address acidification as well. These two examples highlight the urgent need for information on not only the consequences of acidification, but also how affected groups can adapt to these changes.

Like climate change, ocean acidification potentially affects governments, private organizations, and individuals—many of whom have

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