The God Species_ How the Planet Can Survive the Age of Humans - Mark Lynas [113]
Time is running out. The world’s oceans are already more acidic than has probably been the case in at least 20 million years.47 As early at 2016, five years from now, a tenth of the Arctic Ocean could be undersaturated with aragonite for at least one month in the year, making these waters toxic to calcareous organisms. By 2023, when CO2 will reach 428 ppm if current emissions trends continue, 10 percent of the Arctic Ocean will be undersaturated year-round, according to one 2009 modeling study, while by 2050, with CO2 at 534 ppm, this area extends to half the entire ocean.48 Accordingly, at a meeting of marine biologists at the Royal Society in London in July 2009 I was struck by the near-apocalyptic tone of the ensuing scientific paper. Noting that the crisis in the oceans adds to concerns that “anthropogenic CO2 emissions could trigger the Earth’s sixth mass extinction,” the experts warn that as early as 2030 “reefs will be in rapid and terminal decline world-wide,” while by the latter part of the century they could be reduced to “eroding geological structures with populations of surviving biota restricted to refuges.”49
Adhering to the proposed planetary boundary on ocean acidification is therefore critically important to the survival of the marine biosphere. The planetary boundaries expert group accordingly makes a very specific numerical recommendation, setting a maximum level of acidification that would allow coral reefs, plankton, and other marine calcifiers to continue to exist. The crucial number regards the saturation state of aragonite, the most soluble form of pure calcium carbonate, and the one that is used by reef-forming corals and many other species to build their shells. A reasonable margin of safety, the planetary boundaries expert group proposes, would be keeping the aragonite saturation state at 80 percent of preindustrial levels, which should be sufficient “to keep high-latitude surface waters above aragonite undersaturation and to ensure adequate conditions for most coral systems.”50
Given that aragonite saturation in the preindustrial ocean was 3.44 and has now fallen to 2.9, we are currently at 85 percent of preindustrial levels.51 The boundary is approaching rapidly, in other words, but we are still on the right side of it. Meeting it requires humanity to also respect the climate change planetary boundary, of reducing carbon dioxide concentrations in the atmosphere back below 350 parts per million, which in turn requires a carbon-neutral globe by 2050 and measures to extract CO2 from the atmosphere thereafter. This is good news in that meeting the climate change boundary, which we must do anyway, will also protect the oceans from the threat of acidification. Here is another unassailable reason why we must act rapidly to decarbonize the global economy. Doing so will be a colossal challenge, but it is one we can successfully rise to, as I outlined in Chapter 2, by combining the best of modern zero-carbon energy technology with a more creative approach to raising the large sums of capital financing that are necessary to fund the transition away from fossil fuels.
There are some short-term palliative measures that can possibly be taken, though these are no substitute for the central challenge of reducing carbon emissions. One idea is for the use of ground-up olivine rock to be spread as beach nourishment in areas where beach sand is disappearing. Available in immense deposits around the world, olivine gradually dissolves in seawater to create bicarbonate ions out of carbonic acid, helping to fertilize corals at the same time as reducing ocean acidification. If used on a large enough scale, waters around the world’s largest coral reefs could be kept in a more alkaline state by the constant addition of olivine, researchers suggest, and the process would