Industrial civilization is on the brink of crossing Earth’s seventh limit, and may have already done so, according to scientists who have compiled a new report on the state of the world’s life-support systems.
“Ocean acidification is approaching critical thresholds, especially at high latitudes,” the latest Planetary Limits report states. “Increasing acidification poses a growing threat to marine ecosystems.”
The report, by the Potsdam Institute for Climate Impact Research (PIK), builds on years of research showing that there are nine systems and processes – planetary limits – that contribute to the stability of the Earth’s life-support functions.
Six regions have already crossed thresholds where they can no longer function properly. Climate change, the emergence of new species, changes in biosphere integrity, and changes in biogeochemical flows have been identified as being in high-risk areas, while changes in land systems and freshwater systems have also crossed global limits, but to a lesser extent. The data shows that all are getting worse.
However, stratospheric ozone depletion has stabilized and atmospheric aerosol loading has improved slightly, the study said.
Speaking at a press conference to explain the findings, PIK climate physicist and report co-author Lefke Ceasar said there were two reasons why the level of ocean acidification was worrying.
“One is [that] “Current aragonite dissociation, an indicator of ocean acidification, is still within the safe operating range but is approaching a threshold that would cross the safety boundary,” Caesar said.
“Second, several new studies published over the past few years have shown that even current conditions may already be problematic for a variety of marine species. [to] We will reassess what levels are actually safe.”
Ocean acidification is getting worse globally, with its effects most noticeable in the Antarctic and Arctic oceans, she added.
Ocean acidification is the increase in seawater acidity (decrease in pH) due to the absorption of atmospheric carbon dioxide. This process not only has adverse effects on calcifying organisms and can lead to the collapse of food chains, but also reduces the efficiency of the ocean as an important carbon sink.
“This shows the connection between ocean acidification and the health of the biosphere,” Caesar said. “In fact, one of the main messages of our report is that all nine global boundaries are highly interconnected.”
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“This means that any human disturbances to the global environment that we currently observe cannot be treated as separate problems, which is the main way we currently address them, because this kind of approach ignores that components of the Earth system constantly interact with each other, forming a larger network in which changes in one area affect others.”
Planetary boundary science was pioneered by PIK Director Johan Rockström and colleagues in 2009. In that study and two subsequent reports, the researchers identified and quantified boundaries related to climate change, the biosphere, land system changes, freshwater changes, biogeochemical flows, ocean acidification, atmospheric aerosol loading, ozone depletion, and the introduction of new substances, such as synthetic chemicals, into the environment.
Violation of boundaries in each of these territories risks disrupting the stability, resilience and habitability of the planetary condition that has endured for the past 12,000 years and enabled the rise of complex human civilisations.
Rockstrom said the report, released a year after the last one, is the first of what will be annual “planetary health checks” published by PIK.
“We know that the health of the planet is so at risk today that it’s time for us as scientists to step out, to step into uncomfortable territory, and say we’re going to do a scientific measurement of health assessment, a risk assessment, every year, beyond the limits of the planet,” he said. “This isn’t just science, this is science for change.”
Unlike previous iterations of PIK’s planetary limits research, this report has been written and formatted for a general audience rather than published in an academic journal, and Rockstrom and his colleagues said their findings are based on peer-reviewed science.