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 decline, jeopardising food security.

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

• Cultural and ecological heritage: Traditional ecological knowledge, locally adapted marine stewardship practices, and spiritually important marine areas are at increasing risk from acidification.

Ocean acidification threatens the very foundation on which Solomon Islanders depend – healthy marine ecosystems.

Plastic Pollution: A Hidden Stressor on Ocean Resilience

While fossil fuel emissions remain the primary driver of ocean acidification, scientists are increasingly concerned about how plastic pollution can intensify pressure on marine ecosystems and disrupt the ocean’s carbon cycle.

Microplastics are now found across every ocean basin. As they break down, they can leach chemicals, alter microbial activity, and affect plankton – the foundation of marine food webs and a key part of the ocean’s biological carbon pump.

This does not mean plastic pollution causes acidification in the same direct way as CO₂ emissions. But it does mean that reducing plastic leakage is part of protecting the ocean systems that help regulate carbon, support fisheries, and build resilience in the face of wider climate stress.

A Case for Practical Hope

The condition of the ocean is serious, but decline is not inevitable. The most effective responses are those that connect policy, funding, local leadership, and on-ground delivery.

Positive Change for Marine Life works at that intersection: supporting communities to reduce waste leakage, restore critical habitats, strengthen livelihoods, and build locally led systems for long-term marine protection.

Hope is useful only when it’s tied to action. For the ocean, that means investing in the people and places already doing the work.

To respond to ocean acidification and related carbon-cycle disruption, experts call for:

• Rapid fossil fuel reduction: Cutting CO₂ emissions remains the most important step in slowing ocean acidification at its source.

• Protection of marine food webs: Plankton play a critical role in marine ecosystems and the ocean carbon cycle. Reducing pollution, overfishing, and habitat degradation helps protect the systems that underpin fisheries, reef resilience, and carbon regulation.

• Community-led waste management: PCFML’s programs in the Solomon Islands and India help reduce plastic leakage before it reaches coastal and marine ecosystems, while building local systems for long-term environmental protection.

• Stronger global frameworks: As with the Montreal Protocol, coordinated international action matters — but for acidification, global frameworks must address CO₂ emissions, marine pollution, and ecosystem resilience together.

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, clean-ups, outreach, waste systems, restoration, and community partnerships are not symbolic gestures. They are practical interventions that reduce local stress on marine ecosystems and strengthen the communities already working to protect them.

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.