Earth Is on the Brink of Breaching a Seventh of Nine ‘Planetary Boundaries’ That Support Life

Our planet has not passed its latest health check-up. A new assessment of Earth’s life-support systems shows that six out of nine of these crucial processes have crossed their “planetary boundary.” These boundaries are not tipping points—it’s possible to recover from passing them—but they are thresholds signifying we’ve entered higher-risk territory.

On another worrying note, scientists found the planet is close to breaching a seventh planetary boundary: ocean acidification.

In its first edition, a report from the Potsdam Institute for Climate Impact Research (PIK) used years of data and assessments to evaluate the nine planetary boundaries. These life-support systems make Earth resilient and stable. Alarmingly, six of those boundaries have already been crossed, as a similar assessment last year also concluded. The new report adds to that finding, suggesting these six metrics are now moving further into the “red zone,” or what the researchers consider a high-risk zone.

“The overall diagnostic is that the patient, Planet Earth, is in critical condition,” says Johan Rockström, PIK director and pioneer of the Planetary Boundaries Framework, in a statement.

Boundaries that have already been exceeded have to do with climate change, freshwater availability, biodiversity, land use, nutrient pollution (such as phosphorus and nitrogen) and the introduction of synthetic chemicals and plastics to the environment.

Ocean acidification is one of the systems that has not yet crossed its planetary boundary, along with ozone depletion and aerosols in the atmosphere. But while ocean acidification is still in the “green zone,” the new report finds it’s trending in the wrong direction. Scientists now say this metric is on the brink and may cross out of the safe zone in the next few years.

Earth’s oceans absorb carbon dioxide from the atmosphere, providing a valuable carbon sink as humans burn fossil fuels. But this process also makes the oceans more acidic, which can disturb the formation of shells and coral skeletons and affect fish life cycles, per the report.

As ocean acidification approaches the boundary, scientists are particularly concerned about certain regions, like the Arctic and Southern oceans. These areas are vital for carbon and global nutrient cycles, “which support marine productivity, biodiversity and global fisheries,” the report says.

“Looking at the current evolution, I’d say it’s really, really difficult to prevent that [boundary] crossing,” says Levke Caesar, a climate physicist at PIK and an author of the report, to Mongabay’s Sean Mowbray.

Other recent studies indicate the current conditions are already affecting some marine organisms, Caesar said in a press briefing, per the Guardian’s Damien Gayle. As a result, it might be necessary to re-evaluate “which levels can actually be called safe,” she added.

Levels of acidification are different across the world’s oceans. Colder waters, like those in the polar regions, may become more acidic more quickly, because they absorb more carbon dioxide. For some scientists, this suggests that perhaps the boundary has already been breached.

“When you start to think of the nuances of how the ocean works and the importance of some regions over others, I don’t necessarily agree that we’re still in a safe place,” says Helen Findlay, a biological oceanographer at the Plymouth Marine Laboratory in England who was not involved in the report, to Mongabay.

The Planetary Health Check is the first in a series of annual reports led by PIK and organized by the Planetary Boundaries Science initiative. It builds on years of research to inform solutions on how to improve the planet’s health. The health check will also serve as a “mission-control center” for decision-making, per the statement, by using satellite data, A.I. and multiple scientific disciplines—as well as the wisdom of Indigenous peoples, which is something the researchers hope to incorporate more of in following editions.

Even if it is close to its tipping point, ocean acidification is only one of the nine boundaries necessary for regulating the planet. Each process is woven together with the others. To protect the planet, it will take a holistic approach—and according to the team, considering the boundaries all together is the best way to identify the most effective actions to lessen humanity’s impact on the Earth and urgently restore it to a safe state.

“Indeed, one of the main messages of our report is that all nine planetary boundaries are highly interconnected,” Caesar said, according to the Guardian.

Alexa Robles-Gil | | READ MORE

Alexa Robles-Gil is a bilingual science journalist based in New York City. Her work has appeared in the Guardian, Undark, Inside Climate News and more.