Climate Primer #6: The Fifth Planetary Boundary – Ocean Acidification

In the belief that repetition is a key aspect of how most of us learn, I’m continuing the practice of opening with a summary: Climate crisis is the defining issue of the 21st century. The chief signal of climate crisis is global heating which is driven by the buildup of greenhouse gases (in this case, produced by human activity) in Earth’s atmosphere. What is called “climate crisis” though is really the convergence of multiple global crises that threaten to broach key planetary boundaries beyond which organized human life on Earth will be threatened. So far, posts here have addressed four of the nine planetary boundaries as outlined in the schema of the Stockholm Resilience Center: stratospheric ozone depletion, biodiversity loss, toxic substance contamination, and climate change (which, for now, paradoxically, I’m treating as both a component part and the defining feature of global climate crisis).

Today’s post will address ocean acidification, which the SRC describes as follows:

Around a quarter of the CO2 that humanity emits into the atmosphere is ultimately dissolved in the oceans. Here it forms carbonic acid, altering ocean chemistry and decreasing the pH of the surface water. This increased acidity reduces the amount of available carbonate ions, an essential ‘building block’ used by many marine species for shell and skeleton formation. Beyond a threshold concentration, this rising acidity makes it hard for organisms such as corals and some shellfish and plankton species to grow and survive. Losses of these species would change the structure and dynamics of ocean ecosystems and could potentially lead to drastic reductions in fish stocks. Compared to pre-industrial times, surface ocean acidity has already increased by 30 percent. Unlike most other human impacts on the marine environment, which are often local in scale, the ocean acidification boundary has ramifications for the whole planet. It is also an example of how tightly interconnected the boundaries are, since atmospheric CO2 concentration is the underlying controlling variable for both the climate and the ocean acidification boundaries, although they are defined in terms of different Earth system thresholds.

Pre-industrial ocean pH was ~8.2; today, average ocean pH is 8.1, which may not seem like a big difference. For the benefit of readers who may not be familiar with the pH scale (or at least haven’t thought about it much since high school), to quote the National Oceanic and Atmospheric Administration: “[T]he pH scale is logarithmic, so this [0.1 pH unit] change represents approximately a 30 percent increase in acidity.” And, to quote from the Smithsonian: “[Ocean pH] is expected by fall another 0.3 to 0.4 pH units by the end of the century.” Were ocean pH to actually drop another 0.4 units (to 7.7), that would constitute a tripling of ocean acidity and would almost certainly have dire consequences for the “corals and […] shellfish and plankton species” and “ocean ecosystems” mentioned above. Given the extent to which many humans rely on the oceans for food and livelihoods; the centrality of Earth’s oceans to the planet’s climate and ecosystems; and the deep spiritual and aesthetic significance of the oceans and their animals to human societies, it is hard to comprehend the harm that such changes would bring, even when considered in a narrowly anthropocentric sense.

Finally, given that today is the 75th anniversary of the US atomic bombing of Hiroshima (and these primers have elsewhere addressed the threat of nuclear contamination via war or meltdown); the New York Times reported this morning on the possibility that the US-backed Saudi civilian nuclear program might be working towards the construction of a nuclear weapon (although, as the actions of Judith Miller made clear, it’s generally advisable to take the “national security” reporting of the Times with a hunk of salt); and that many recent actions of the Administration in DC (withdrawal from the Intermediate-Range Nuclear Forces Treaty and undermining the New START Treaty, among them) have moved the world much closer to “midnight” as reflected by the Doomsday Clock of the Bulletin of the Atomic Scientists, I’ll close by sending support and condolences to anyone touched by the devastating recent explosion in Beirut. Although – contrary to online rumors – the blast was not nuclear, and – contrary to White House rumors – nor was it, evidently, caused by “a bomb” – I’ve found videos of the explosion and the ruins and human injuries left in its aftermath at once so staggering and gut-wrenching that I’d hope no viewer could be left unmoved at the harm done, and by the evidence of the destructive power humans now, inadvertently or otherwise, can unleash. For anyone looking to delve deeper into the context within Lebanon which allowed such a horrible accident to occur, I encourage you to watch yesterday’s Democracy Now! segment with Rami Khouri.

4 thoughts on “Climate Primer #6: The Fifth Planetary Boundary – Ocean Acidification

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