TL;DR: A new report on planetary boundaries indicates that we are nearing a dangerous threshold that could render Earth's environment unsustainable for human life. Ocean waters are rapidly decreasing in pH levels, with acidification posing a significant threat to marine ecosystems.
According to the latest study from the Potsdam Institute for Climate Impact Research (PIK), ocean acidification is approaching a critical threshold. The researchers warn that the seventh planetary boundary has almost been breached, making it extremely difficult, or even impossible, to maintain the environmental balance that has supported human civilization for thousands of years.
Planetary boundary science was established in 2009 by Johan Rockström and other PIK scientists. This framework describes the impact of human activities on Earth's biosphere, identifying specific thresholds beyond which the environment may be unable to self-regulate. If all nine planetary boundaries are breached, the period of stability that humankind has enjoyed during the Holocene will likely be replaced by very different – and extremely hostile – planetary conditions.
The nine systems described by PIK's planetary framework include the following boundaries: climate change; the introduction of novel entities into the ecosystem (synthetic chemicals); depletion of the ozone layer in the stratosphere; increase in atmospheric aerosol; ocean acidification; biogeochemical flows; freshwater changes; land system changes; and biosphere integrity.
According to the latest report, ocean acidification is now almost beyond the point of no return. The oceans are absorbing increasing amounts of greenhouse gases from the atmosphere, especially at higher latitudes, and this process poses an existential threat to calcifying organisms. Entire food systems could break down, and the ocean's efficiency as a carbon sink would be diminished accordingly.
Ocean acidification and biosphere integrity are deeply interconnected, warned PIK climate physicist Levke Caesar. Several new studies published over the past few years suggest that even the current conditions of oceanic waters could be considered "problematic" and essentially unsafe for various marine organisms.
Caesar stated that "one of the main messages of our report is that all nine planetary boundaries are highly interconnected." The nine issues described in the planetary framework should be viewed as parts of a single environmental problem because Earth's systems are constantly interacting, and any change in one area affects the others.
Researchers have indicated that the planet's health is at such risk that scientists must work harder to convey this message to a larger audience. PIK researchers are now committing to publishing new measurements of planetary boundaries' thresholds every year, producing reports that are accessible to a broader audience rather than academics alone.