- A first of its kind Planetary Health Check by an international team of scientists indicates that six of nine planetary boundaries are not only transgressed, but are moving further into zones of risk. In addition, recent research shows that a seventh boundary, ocean acidification, is on the verge of transgression.
- Intensifying ocean acidification spells problems for marine life, fisheries and economies. Based on current human CO₂ emission trajectories, this boundary may be breached in a few years, say experts. Others argue this threshold may already have been crossed, with regional acidification above safe limits.
- Together, the nine planetary boundaries identify limits within which Earth systems can operate safely to maintain the planet’s habitability. Transgressing boundaries heightens risks of breaching tipping points that would bring about irreversible shifts to the planet, threatening humanity and life as we know it.
- This inaugural Planetary Health Check is the first of yearly scheduled reports on the wellbeing of Earth systems. Annual reports are now needed due to humanity’s rapid crossing of planetary boundaries, and due to the urgency of providing up to date scientific data to policymakers.
The first ever pulse check of the planet’s health shows that the Earth is far beyond it’s safe operating space for humanity. Six of nine key planetary boundaries are already transgressed, and continue moving deeper into risk zones that could threaten our planet’s habitability. A seventh boundary, ocean acidification, is on the verge of transgression and may exceed safe limits in a matter of years.
That’s according to the first-ever Planetary Health Check, a nearly 100 page report produced by the new Planetary Boundaries Science (PBScience) initiative led by Earth System scientist Johan Rockström and the Potsdam Institute for Climate Impact Research (PIK), and supported by the Planetary Guardians and other partners.
Boundaries for climate change, biosphere integrity, land system change, freshwater change, biogeochemical flows, and the introduction of novel entities (such as synthetic chemical pollutants) are all surpassed, as a study published last year found.
Worryingly, in this latest report, all those already transgressed are moving deeper into the red zone, says Levke Caesar, a report author and co-leader on planetary boundaries at the Potsdam Institute for Climate Impact. “Our updated diagnosis shows that vital organs of the Earth system are weakening, leading to a loss of resilience, and rising risks of crossing [irreversible] tipping points.
“We see it’s not changing [for the better]. It is actually getting worse,” she says.
The breach of planetary boundaries heightens the risk of permanently damaging Earth’s life support functions, with the report warning that the world is entering a “dangerous new era.” Symptoms of boundary transgression already being seen include the rapid extinction of species, extreme heat, drought and storms, record wildfires, reduced crop and fisheries productivity, and freshwater scarcity.
“We are really risking losing the planet as we know it, and this risk is increasing the further we go into the red zones,” Caesar adds.
Worse still, the health check found that the ocean acidification boundary is nearing transgression, and may pass its global “safe operating space” threshold in the next few years, says Caesar. Acidification — driven by climate change-fueling CO2 emissions — could severely impact marine ecosystems and the global economy.
Graphic showing that six of the nine planetary boundaries have already transgressed the “safe operating space for humanity,” with ocean acidification on the verge of entering the red zone. Stratospheric ozone depletion is considered stable, while only atmospheric aerosol loading is trending in a positive direction. Image from Planetary Health Check 2024, designed by Globaïa.
Ocean health on the brink
For now, the ocean acidification boundary remains within the green safe operating space, according to scientists, but it is on the precipice. Studies show rising acidification could devastate fragile coral reefs and phytoplankton populations, considered the foundation of marine food webs. As acidification accelerates, global fisheries could degrade and even collapse, deepening human suffering and worsening hunger in vulnerable communities, and inflicting billions of dollars in global costs to economies.
Ocean acidification is driven by the same cause as climate change: rising atmospheric CO2 concentrations due to rampant fossil fuel emissions. The outlook for staying within the safe limit for this boundary appears bleak. “Looking at the current evolution, I’d say it’s really, really difficult to prevent that [boundary] crossing,” Caesar says.
The report uses surface aragonite saturation as an indicator for ocean acidification because it correlates to carbonate ion concentration. As atmospheric carbon dioxide is absorbed by the ocean, more-and-more carbonic acid is created, which releases hydrogen ions to lower pH and aragonite saturation. Declining pH in seawater means more ocean acidity and spells trouble for marine life that relies on calcium carbonate for shell formation.
The current safe operating limit is set at 2.75 aragonite saturation and is based on pre-industrial levels of 3.44. Levels below 3 can lead to some marine organisms becoming stressed, and if levels drop below 1 shells can begin to dissolve. Today, global aragonite saturation stands at 2.80. Passing that safe limit does not mean an immediate drop off a cliff, explains Caesar, but problems for marine life and the ocean’s food web will “definitely start to look more and more severe.”
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Report: Caesar, L., Sakschewski, B., Andersen, L S., Beringer, T., Braun, J., Dennis, D., Gerten, D., Heilemann,. A., Kaiser, J., Kitzmann, N.H., Loriani, S., Lucht., W Ludescher, J., Martin, M., Mathesius, S., Paolucci, A., te Wierik, S., & Rockström, J. (2024), Planetary Health Check Report 2024. Potsdam Institute for Climate Impact Research, Potsdam, Germany.
Mongabay, 23 September 2024. Press release.
