The State of the Oceans Is Worsening as Human Pressure Accelerates

• Climate change

The state of the oceans is becoming increasingly concerning. The ocean is absorbing much of the excess heat generated by climate change and a significant share of the carbon dioxide released by human activities, but this natural buffering capacity comes at a cost. Rising temperatures, sea-level rise, pollution, overexploitation of marine resources and biodiversity loss are placing growing pressure on marine ecosystems.

The United Nations’ Third World Ocean Assessment, presented on June 8, 2026, provides one of the most comprehensive overviews of the current condition of the world’s oceans. The assessment brings together the work of hundreds of experts from around the world and examines the environmental, economic and social dimensions of changes taking place in the marine environment.

Its overall conclusion is clear: human pressures on the oceans are not only serious, but they are also accumulating and intensifying.

Sea Levels Are Rising at an Increasing Rate

One of the clearest indicators of how the ocean is changing is the rise in global mean sea level. Between 2013 and 2023, global sea levels increased at an average rate of 4.3 millimeters per year, more than twice the 2.1 millimeters per year recorded between 1993 and 2002.

A few millimeters may seem insignificant, but the impact becomes much more substantial when the increase accumulates year after year. Sea-level rise is also not uniform around the world, meaning that some coastal regions can experience increases above the global average.

The rise is mainly driven by two processes associated with global warming. First, seawater expands as it becomes warmer. Second, melting glaciers and large land-based ice sheets add more water to the oceans.

For coastal communities, the consequences can be significant. A higher average sea level means that high tides can reach farther inland and increases the exposure of coastal areas to flooding, erosion and extreme events such as storm surges.

The Ocean Is Absorbing an Extraordinary Amount of Heat

The ocean plays a fundamental role in regulating Earth’s climate. Since 1955, it has absorbed more than 90% of the excess heat accumulated within the climate system.

This enormous heat-absorbing capacity has limited some of the warming that would otherwise have affected the atmosphere and land surface directly. However, storing this additional heat is also changing the physical and biological conditions of the marine environment.

One particularly significant finding from the United Nations assessment is that approximately 16% of the total increase in ocean heat content recorded since 1955 occurred between 2018 and 2023. That period represents only a small portion of the historical record.

Ocean warming is also unevenly distributed. The assessment identifies particularly strong warming across large parts of the Atlantic and in southern areas of the Indian and Pacific oceans.

Increasing water temperatures can alter species distributions, contribute to marine heatwaves, damage sensitive ecosystems such as coral reefs and affect the conditions under which marine organisms survive and reproduce.

Changes in Ocean Currents Could Have Global Consequences

Ocean currents are another critical component of the climate system. They transport heat, nutrients and oxygen around the planet and influence atmospheric conditions as well as the health and distribution of marine ecosystems.

Changes in ocean circulation can affect species distributions, fisheries and regional climate patterns. This is why changes in major ocean currents remain a major area of scientific research.

The evolution of Atlantic circulation is of particular interest because of its potential implications for Europe and other parts of the Northern Hemisphere. However, scientists still face significant uncertainties regarding the magnitude and speed of some of these changes.

This highlights one of the central challenges of understanding the state of the oceans: the marine system is extremely complex, and its different components are closely interconnected.

Plastic Pollution Has Reached a Global Scale

Plastic pollution has become one of the major threats facing marine ecosystems. According to the United Nations assessment, approximately 52.1 million tonnes of plastic waste enter the ocean every year.

A significant portion of this material eventually breaks down into increasingly smaller particles. An estimated 24.4 trillion microplastic particles are found in the upper layers of the ocean.

These particles can originate from a wide range of sources. Packaging and disposable products, textiles, vehicle tires, paints, fishing gear and other materials can all contribute to marine plastic pollution.

The problem extends far beyond beaches and coastal waters. Plastic waste can travel vast distances through ocean currents, sink into deeper waters or become incorporated into different marine ecosystems.

More than 4,000 marine species are reported to be affected by different forms of marine debris. Plastic pollution therefore represents a threat not only to biodiversity but also to economic activities such as fishing and tourism.

Much of the Deep Ocean Remains Unknown

Despite major technological advances over recent decades, a huge proportion of the ocean remains poorly understood.

By 2025, only 27.3% of the global seafloor had been mapped. This means that most of the deep ocean still contains major gaps in scientific knowledge.

The challenge goes beyond simply producing maps. Scientists still have limited information about numerous species, microbial communities, biological processes and deep-sea ecosystems.

This lack of knowledge has become particularly important as interest in deep-sea mineral and biological resources increases. Exploring and exploiting these resources could create additional pressures on ecosystems whose structure and functioning are not yet fully understood.

The United Nations assessment also highlights major differences in scientific and technological capacity between countries and regions. Expanding ocean research and improving access to data and technology will be essential for making sound environmental decisions.

The Health of the Ocean Directly Affects Millions of People

The condition of the oceans is not an issue restricted to fishing communities or major ports. Approximately 37% of the world’s population lives within 100 kilometers of a coastline, while around 11% lives on land less than 10 meters above sea level.

Coastal areas concentrate a significant share of the world’s population, infrastructure and economic activity. Tourism, shipping, fishing, energy production and numerous industries depend directly or indirectly on healthy and functioning marine ecosystems.

Small-scale fisheries are particularly important. They provide employment for tens of millions of people and represent a vital source of food and income for many coastal communities.

The degradation of the oceans can therefore have direct economic and social consequences. Biodiversity loss, habitat degradation, pollution and warming can reduce the availability of marine resources and increase the vulnerability of communities that depend on the sea.

A New International Agreement Creates a Path for Protecting the High Seas

There are also reasons for cautious optimism. In 2026, an international agreement designed to protect marine biodiversity in areas beyond national jurisdiction entered into force.

The agreement on marine biodiversity in areas beyond national jurisdiction establishes an international framework for improving the conservation of biodiversity in the high seas. It provides mechanisms to advance marine protected areas, marine genetic resources and environmental impact assessments.

Its entry into force represents an important milestone following years of international negotiations. However, effective protection of the high seas will ultimately depend on cooperation between countries and on the practical implementation of the measures established by the agreement.

Ocean governance remains one of the major challenges because different activities, including fishing, shipping, environmental conservation and resource exploitation, are often regulated through separate international frameworks.

What Needs to Change to Protect the Oceans

The global assessment makes clear that there is no single solution capable of reversing all the pressures affecting the ocean. The response must address climate change, pollution, biodiversity loss and the exploitation of marine resources simultaneously.

Reducing greenhouse gas emissions is essential to limit ocean warming and future sea-level rise. At the same time, plastic pollution needs to be reduced throughout the entire product life cycle, while waste management must improve and economies must become less dependent on disposable products.

Sustainable fisheries management is also critical to prevent the depletion of fish populations and ensure that marine resources can continue to provide food and livelihoods in the future.

These measures need to be combined with greater protection and restoration of marine and coastal ecosystems, including coral reefs, mangroves, seagrass meadows and other habitats that play an important role in supporting biodiversity.

Greater investment in ocean science and monitoring will also be necessary. The better scientists understand the transformations taking place beneath the surface, the better governments and communities will be able to anticipate risks and develop effective policies.

The state of the oceans reflects, to a large extent, the relationship between human activity and the natural systems that support life on Earth. The ocean continues to absorb heat, store carbon and provide food, employment and coastal protection, but its capacity to absorb additional pressures is not unlimited.

The Third World Ocean Assessment highlights precisely this challenge: protecting the ocean is not simply about conserving marine life. It is also about protecting economies, coastal communities and an essential component of Earth’s climate system.