ANNEX F-1: Background on Ocean Acidification
Scientists estimate that average surface ocean pH has fallen by about 0.1 pH units
between pre-industrial times and today.1 Although this may appear to be a relatively small
change, it is nonetheless equivalent to a 26% increase in acidity. If we continue on the
business as usual trajectory for fossil fuel use and rising atmospheric CO2 (the
Intergovernmental Panel on Climate Change’s (IPCC) worst case scenario), pH is projected to
drop by around 0.3-0.32 units by the end of the 21st century, representing an increase in
acidity of 100-109% over baseline levels for the period 1986-2005.2
Acidification of both offshore and coastal waters is expected to have profound
implications for many marine species and ecosystems. Although the nature and scale of
impacts is likely to vary across different species and habitats in a complex manner,3 some of
the greatest negative impacts are expected to fall on highly calcifying organisms, including
corals, mollusks, and echinoderms, by both reducing calcification rates and increasing
dissolution and erosion. 4 This is because rising acidity results in both lower overall
concentrations of carbonate and a reduction in the ‘saturation states’ for the various carbonate
minerals on which calcifying organisms rely.5 Impacts such as the observed thinning of shells
of pteropod mollusks in the Southern Ocean6 and losses of oyster larvae in hatcheries on the
Pacific coast of America,7 which have been attributed with medium to high confidence as
direct consequences of ocean acidification, may act as sentinels of the potential for much
more widespread changes in the future if current trends in emissions continue.8 It is not just
1
R.A. Feely & S.C. Doney & S.R. Cooley, Ocean Acidification: Present Conditions and Future Changes in a
High-C02 World, 22(4) OCEANOGRAPHY 36, 37 (2009); C. Turley & J.P. Guttuso, Future Biological and
Ecosystem Impacts of Ocean Acidification and Their Socioeconomic-Policy Considerations, 4(3) CURRENT
OPINION IN ENVIRONMENTAL SUSTAINABILITY 278 (2012).
2
Ciais, P., C. Sabine, G. Bala, L. Bopp, V. Brovkin, J. Canadell, A. Chhabra, R. DeFries, J. Galloway, M.
Heimann, C. Jones, C. Le Quéré, R.B. Myneni, S. Piao and P. Thornton (2013) Carbon and Other
Biogeochemical Cycles. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group
I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)].
Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA at 531.
3
Turley & Guttuso, supra note 1.
4
Wong, P.P., I.J. Losada, J.-P. Gattuso, J. Hinkel, A. Khattabi, K.L. McInnes, Y. Saito, and A. Sallenger (2014)
Coastal systems and low-lying areas. In: Climate Change 2014: Impacts,Adaptation, and Vulnerability. Part A:
Global and Sectoral Aspects. Contribution of Working Group II to the Fifth Assessment Report of the
Intergovernmental Panel on Climate Change [Field, C.B., V.R. Barros, D.J. Dokken, K.J. Mach, M.D.
Mastrandrea, T.E. Bilir, M. Chatterjee, K.L. Ebi, Y.O. Estrada, R.C. Genova, B. Girma, E.S. Kissel, A.N. Levy,
S. MacCracken, P.R. Mastrandrea, and L.L.White (eds.)]. Cambridge University Press, Cambridge, United
Kingdom and New York, NY, USA, pp. 361-409.
5
C. Turley, C. (2013) Chapter 2: Ocean Acidification (2013). In: K.J. Noone, U.R. Sumaila, R.J. Diaz [Eds],
Managing Ocean Environments in a Changing Climate: Sustainability and Economic Perspectives, (2013) at 15.
6
N. Bednarše & G.A. Tarling & D.C.E. Bakker & S. Fielding & E.M. Jones & H.J. Venables & P. Ward & A.
Kuzirian & B. Lézé & R.A. Feely, & and E.J.Murphy, (2012) Extensive Dissolution of Live Pteropods in the
Southern Ocean, 5 NATURE GEOSCIENCE 881 (2012).
7
A. Barton & B. Hales & G.G. Waldbusser & C. Langdon & R.A. Feely (2012) The Pacific Oyster, Crassostrea
gigas, Shows Negative Correlation to Naturally Elevated Carbon Dioxide Levels: Implications for Near-Term
Ocean Acidification Effects, 57(3) LIMNOL. OCEANOGR. 698 (2012).
8
Pörtner, H.-O., D.M. Karl, P.W. Boyd,W.W.L. Cheung, S.E. Lluch-Cota, Y. Nojiri, D.N. Schmidt, and P.O.
Zavialov (2014) Ocean systems. In: Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part A:
Global and Sectoral Aspects. Contribution of Working Group II to the Fifth Assessment Report of the