Zimmerman column: Ocean acidification – the other CO2 problem

Human activity recently sent the concentration of CO2 in the atmosphere beyond 400 ppm for the first time in more than 4 million years. This threshold may be a point-of-no-return with dire consequences for climate warming. However, CO2 is not just a greenhouse gas. Nearly half the human-released CO2 is absorbed by the oceans, slowing climate warming, which is a good thing. Unfortunately, the absorbed CO2 reacts with water to produce carbonic acid, lowering the pH of seawater through a process called ocean acidification (OA), which is not such a good thing.

Organisms that make limestone shells or skeletons, including corals, clams, oysters, and plankton that feed important fisheries, may struggle in an acidified ocean. Recent failures of oyster hatcheries in the Pacific Northwest driven by acidified upwelling and the double-whammy impacts of ocean warming and OA on coral reefs highlight increasing effects on marine life across the globe. However, OA also increases the availability of CO2 for photosynthesis, producing winners, as well as losers, in a changing climate. OA will benefit highly successful and ecologically important seagrasses, and may help Chesapeake Bay eelgrass tolerate warmer temperatures. This balance between winners and losers will have dramatic effects on ocean biota in a hot and sour sea.

OA has already produced a drop in mid-ocean pH, but local processes in coastal environments like Chesapeake Bay can hide global impacts. The high variability in coastal pH driven by weather, algal blooms and sediment runoff, combined with complex interactions between winners and losers, makes it difficult to predict the future of coastal ecosystems on which we depend for food, commerce, storm protection and recreation. However, federally supported research is helping us develop a predictive understanding of these processes from local to global scales. Although our knowledge is imperfect, we know that Earth is undergoing climate change coupled with ecosystem disruption and species extinction at an unprecedented rate. In acknowledging the hand of man, some have proposed the designation of a new geologic epoch — the Anthropocene — because human activity is leaving a permanent mark in the geologic record of Earth.

Knowledge provided by the scientific method has changed the world, and our view of humanity’s role in it, unlike any other endeavor. However, scientifically demonstrable truths can meet with resistance when they run counter to established political and economic interests. (…) The success of our democratic system requires the use of objective, scientific knowledge to support public policy. Research is hard work, and it should not shock us that people are paid to do it. Today, our burgeoning understanding of the consequences of carbon emission threatens powerful fossil fuel interests. When science releases unpleasant warnings regarding OA, sea level rise, and extreme weather, it is wiser to listen to the message than to punish the messenger.

The geologic record emphasizes the resiliency of life on Earth by recording spurts of increasing diversity following previous climate catastrophes, as survivors evolve to exploit opportunities created by mass extinction. Natural weathering processes will eventually neutralize the rising acidity of the oceans, but this will require many thousands of years to restore the equilibrium disrupted by human release of CO2. Some species are adapting to the new climate, but many others are going extinct. Humans live on land, but our ocean world is increasingly important for human survival. We will have to work hard, and quickly, to preserve the viability of that ocean world for future generations.

Richard C. Zimmerman, Richmond Times – Dispatch, 7 October 2016. Article.

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OA-ICC HIGHLIGHTS

Ocean acidification in the IPCC AR5 WG II

OUP book