Industrial civilization is close to crossing a seventh planetary boundary, and may have already crossed it, according to scientists who compiled the latest report on the state of the world’s life-support systems.
“Ocean acidification is approaching a critical threshold”, especially in higher latitude areas, says the latest Planetary Boundaries report. “The growing acidification poses an increasing threat to marine ecosystems.”
The report, from the Potsdam Institute for Climate Impact Research (PIK), builds on years of research showing there are nine systems and processes – the planetary boundaries – that contribute to the stability of the planet’s life-supporting functions.
Thresholds at which they can no longer function properly have already been breached in six. Climate change, the introduction of new entities, change in biosphere integrity and modification of biogeochemical flows are judged to be in high-risk zones, while planetary boundaries are also crossed in land system change and freshwater change, but to a lesser extent. According to the data, all have worsened.
However, stratospheric ozone depletion has remained stable, and there has been a slight improvement in atmospheric aerosol loading, the research says.
At a briefing detailing the findings, Levke Caesar, a climate physicist at PIK and co-author of the report, said there are two reasons why the levels of ocean acidification are worrying.
“One is [that] the ocean acidification indicator, which is the current aragonite separation state, while still in the safe operating space, is approaching the threshold to exceed the safe boundary,” Caesar said.
“The second is that there are actually several new studies published over the past year that indicate that even these current conditions may already be problematic for a variety of marine organisms, indicating a need. [to] reevaluate what levels can really be called safe.”
Ocean acidification has worsened globally, with the effects felt most in the Southern Ocean and the Arctic Oceanshe added.
Ocean acidification is the phenomenon of increasing acidity (decreasing pH) in seawater due to the absorption of atmospheric CO2. The process not only harms calcifying organisms, potentially leading to food web breakdown, but also reduces the ocean’s effectiveness in acting as a vital carbon sink.
“This illustrates the connection between ocean acidification … and biosphere integrity,” Caesar said. “One of the main messages of our report is indeed that all nine planetary boundaries are highly interconnected.
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“This means that any human disturbance of the global environment that we observe at the moment … cannot be addressed as if they were separate issues, and that is how they are mainly dealt with at the moment. Because this type of approach ignores that the components of the Earth system constantly interact and form a large network where changes in one area affect the others.”
Planetary frontier science was started in 2009 by Johan Rockstrom, the director of the PIK, and others. In that research and two subsequent reports, the researchers identified and quantified boundaries related to climate change, biosphere, land system change, freshwater change, biogeochemical fluxes, ocean acidification, atmospheric aerosol loading, ozone layer depletion and the introduction of new entities, such as e.g. synthetic chemicals, to the environment.
Transcending boundaries in each of those areas risks disrupting the stability, resilience and livability of the state of the planet that has persisted for the past 12,000 years and allowed the rise of complex human civilization.
The report, which came a year after the last, is the first of what will now be annual “planetary health surveys” published by PIK, Rockstrom said.
“We recognize that the health of the planet is in such danger today that we in science must also act now and step straight into the uncomfortable zone and say that we now commit ourselves to produce a scientific measurement of the whole health assessment every year – a risk assessment – across all planetary boundaries,” he said. “It’s much more than science, it’s science for change.”
Unlike previous iterations of PIK’s research on planetary boundaries, the report does not appear in an academic journal, but is instead written and formatted for a popular audience. Rockstrom and his colleagues said the findings were based on peer-reviewed science.
