The ocean has always been Earth’s greatest stabiliser. Covering more than 70% of the planet, it regulates climate, absorbs carbon dioxide, generates oxygen, and supports ecosystems that billions of people depend upon. But new research shows that the ocean’s ability to perform these vital roles is faltering under unprecedented stress. 

Last week, scientists at the Potsdam Institute for Climate Impact Research (PIK) released the 2025 Planetary Health Check, an annual assessment of the Earth’s critical life-support systems.

The report delivered a chilling milestone: that seven out of nine key, ‘planetary boundaries,’ the systems that keep Earth stable, have been crossed.

Ocean acidification has just joined that list for the first time. 

“The ocean is our planet’s life-support system. Without healthy seas, there is no healthy planet,” warned Dr. Sylvia Earle, veteran oceanographer.

“Acidification is now a flashing red warning light on the dashboard of Earth’s stability. Ignore it, and we risk collapsing the very foundation of our living world.”

Fire coral, before and after calcification (Photo: Caitlin Seaview Survey)

What is Ocean Acidification?

Ocean acidification occurs when excess carbon dioxide (CO2) dissolves into seawater, forming carbonic acid. This chemical shift reduces the availability of carbonate ions, the building blocks many marine organisms need. 

Since the Industrial Revolution, ocean surface pH levels have dropped by about 0.1 units, a seemingly small shift, but one that represents a 30-40% increase in acidity.

Why This Matters in the Solomon Islands

The Solomon Islands, like many Pacific nations, is intimately tied to the health of its reefs, coastal fisheries, and marine ecosystems. Here’s how acidification intersects with local realities:

• Coral reef vulnerability: Reefs in the Solomons already face stress from warming, bleaching, disease, and pollution. Acidification adds a chemical stressor, making reef-building slower and reducing recovery potential.

• Fisheries and livelihoods: Many communities depend on small fish, shellfish, molluscs, and reef-associated species. If the base of the food web weakens, catches shrink, and nutritional security is jeopardised.

• Coastal protection: Healthy reefs act as natural breakwaters. Diminished calcification or reef degradation undermines this buffer, increasing vulnerability to storm surges and erosion.

• Cultural and ecological heritage: Traditional ecological knowledge, locally adapted marine stewardship, and sacred marine areas risk losing resilience under accelerated chemical changes.

In short: acidification doesn’t just happen “out there.” It threatens the very foundation of ecosystems on which Solomon Islanders depend.

Plastic Pollution: A Hidden Driver of Acidification 

While fossil fuel emissions are the primary culprit, scientists are increasingly drawing attention to the role of plastic pollution in worsening ocean acidification. Plastics may seem inert, but in reality, they act as amplifiers of chemical stress in marine environments.

Microplastics, which now blanket nearly every ocean basin, can leach chemicals and carbon that alters seawater chemistry. These are consumed by bacteria that produces more CO2, intensifying localised acidification.

Moreover, plastic waste harms and interferes with the ability of plankton, the base of the marine food chain, to remove carbon from the water. 

This means plastic pollution doesn’t just harm animals physically, it also alters the oceans chemistry, increasing acidity. It’s a stark reminder that addressing the health of the ocean requires both tackling carbon emissions and plastic pollution. 

Signs of Hope

Despite the dire picture, there are reasons to act. Humans have united before, from international treaties to community-led programs like the work of Positive Change for Marine Life (PCFML). Every piece of plastic removed, reef restored, and community educated contributes to a healthier ocean. 

To slow acidification, experts call for:

• Rapid fossil fuel reduction: Transition to renewable energy and reduced CO2 emissions.
• Plastic pollution management: Reducing single-use plastics and improving waste collection. PCFML programs in the Solomon Islands and India serve as models for community-led waste management.
• United global action: Just as the Montreal Protocol saved the ozone layer, an enforceable global framework on ocean health could reverse acidification trends. 

Acting Before It’s Too Late 

Time is critical. CO2 can remain in the ocean for centuries. Each year of delay locks in further damage. 

The ocean has long buffered and supported humanity. Now it is signalling distress. At PCFML, every clean-up, outreach event, and community partnership is a small but essential step in answering that distress call. 

The 2025 Planetary Health Check is a call to action: collective global change combined with grassroots engagement is the only way to keep Earth’s life-support systems within safe limits. The window is closing, but it is not yet shut.