TO HOME

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By 2050, the Ocean Could Become
as Acidic as a Soft Drink

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▲ The image illustrates how increasing carbon dioxide changes ocean chemistry and places marine ecosystems at risk.Source: Sunhak Peace Prize

“At this rate, the ocean could become as acidic as cola.” It sounds exaggerated, doesn’t it? But once we look at the chemistry step by step, the comparison becomes uncomfortably clear.

Imagine leaving a tooth in a glass of cola. Carbonic acid gradually wears away the hard enamel, making the tooth softer and weaker. A similar chemical process is now unfolding across the world’s oceans.

Carbon dioxide from factories, power plants, and vehicles does not remain only in the atmosphere. Some of it dissolves into seawater and forms carbonic acid (H₂CO₃), which releases hydrogen ions (H⁺). As those ions increase, seawater pH falls and the ocean becomes more acidic.

The problem goes further. This process also reduces carbonate ions, the material corals, oysters, and many other marine organisms need to build shells and skeletons. When carbonate becomes scarce, they struggle to grow. In more acidic water, structures they have already formed may even begin to dissolve.

This is not simply the marine version of a damaged tooth. It means that part of the physical foundation supporting the ocean ecosystem is weakening quietly, day after day. The balance of marine life is being pushed toward a dangerous tipping point.

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What Is Ocean Acidification?

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Let’s briefly return to chemistry class. pH is measured on a scale from 1 to 14. Lower numbers are more acidic, while higher numbers are more alkaline. But pH is not a simple linear scale; it is logarithmic. That means a one-point drop represents a tenfold increase in hydrogen-ion concentration.

The pre-industrial ocean had an average pH of about 8.21. By 2023, it had fallen to around 8.10. A change of roughly 0.1 may look small, but it means the ocean is already about 30% more acidic than it was before industrialization.

The speed is just as troubling. Scientists say the current pace of acidification is extremely rapid by geological standards. Marine species are being asked to adapt in decades to changes that would normally unfold over far longer periods.

▲ Average ocean pH declined from about 8.21 before industrialization to 8.10 by 2023. The chart also shows the scale of the 2023–2025 global coral bleaching event.Source: NOAA; IPCC Sixth Assessment Report

▲ Ocean pH has declined steadily over recent decades, showing that seawater is becoming progressively more acidic.Source: Nicolas Gruber and Luke Gregor

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Coral Bleaching:
The Ocean’s Distress Signal

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Have you heard of coral bleaching, the process that turns colorful reefs ghostly white? Corals themselves are naturally pale or translucent. Their bright colors come from microscopic algae called zooxanthellae, which live inside coral tissue.

The algae use sunlight to make food and share nutrients with the coral. In return, the coral provides a protected home. It is a remarkably effective partnership. But when seawater becomes too warm or chemically stressful, the coral expels the algae.

Without its algae, the coral loses both its color and much of its food supply, leaving the white skeleton visible. If the stress continues, the coral may starve and die. Bleaching is not always immediate death, but it is a clear distress signal.

Australia’s Great Barrier Reef, the world’s largest reef system, has experienced repeated mass-bleaching events. The severe events of 2016 and 2017 caused extensive coral mortality, showing how quickly a vast ecosystem can be transformed.

▲ The photograph shows the visible contrast between healthy coral and coral affected by bleaching.Source: Sunhak Peace Prize

▲ The chart summarizes changes in coral cover and condition across the Great Barrier Reef.Source: Australian Institute of Marine Science

The crisis did not stop in Australia. From January 2023 through mid-2025, NOAA tracked the fourth global coral bleaching event, the most extensive recorded to date. Bleaching-level heat stress affected roughly 84% of the world’s reef area across 83 countries and territories.

The four recognized global events—1998, 2010, 2014–2017, and 2023–2025—show a worrying pattern. Each has reached farther than the one before it, like a sequence of alarm bells growing louder.

▲ The proportion of global reef area exposed to bleaching-level heat stress rose from about 20% in 1998 to 84% during the 2023–2025 event.Source: NOAA Coral Reef Watch; International Coral Reef Initiative

Why do reefs matter so much? Although coral reefs occupy less than 1% of the ocean floor, about one-quarter of marine species depend on them. That is why they are often called “the rainforests of the sea.”

When a reef collapses, spawning grounds, shelter, and food webs can collapse with it. The consequences also reach millions of people who depend on reef fisheries, coastal protection, and tourism.

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Shellfish and Fish
Are Not Safe Either

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Corals are not the only organisms at risk. Oyster hatcheries along the Pacific coast of North America have experienced periods when more acidic seawater made it difficult for newly hatched oysters to form shells. For farmers, that means lost income. For consumers, it is a warning about the future of seafood supplies.

Pteropods—tiny swimming snails often called “sea butterflies”—are also vulnerable. They are eaten by krill, salmon, and other marine animals. Experiments and field observations show that their delicate shells can weaken or dissolve in more acidic water. When organisms near the bottom of the food web decline, the effects can travel all the way to larger fish and, eventually, our dinner tables.

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The International Community
Has Not Stood Idle

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Fortunately, the world is not simply watching this crisis unfold. The ocean has no borders, so an effective response must cross borders too.

One important initiative is OARS—Ocean Acidification Research for Sustainability. It brings scientists, observation networks, and policymakers together to improve monitoring, understand biological impacts, and turn research into practical policy. Put simply, it helps the world see the ocean’s changing condition as one connected picture rather than as scattered local problems.

For climate-vulnerable island states, reliable ocean data can support international advocacy and national planning. Scientific evidence gives smaller countries a stronger voice when they call for faster emissions reductions, adaptation finance, and protection of marine ecosystems.

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What We Can Do Is Closer
Than You Think

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▲ Protecting the ocean requires both large-scale emissions cuts and practical choices in our communities and daily lives.Source: Sunhak Peace Prize

At its root, ocean acidification comes from carbon dioxide. The central solution is therefore clear: we must reduce greenhouse-gas emissions. But international policy and individual action are not competing approaches. They are two parts of the same response.

The list may seem ambitious, but several of these steps can begin today. For generations, the ocean has acted as a shield, absorbing a large share of humanity’s excess carbon dioxide and heat. Now it is our turn to protect that shield.

A future in which the ocean becomes as acidic as a soft drink is not inevitable. Bleached coral skeletons and failing oyster beds are warnings, not a final ending.

What we choose now will help determine the kind of ocean future generations inherit. That choice begins with public policy, business decisions, and the ordinary actions we take each day.

Written by Sharon Choi
Director of Planning, Sunhak Peace Prize Secretariat