Just as is the case with the climate, air pollution and ecosystems on dry land, human activities are transforming and endangering the oceans as well — those that a new United Nations report, compiled by 550 experts from 86 countries around the world, describes as "the foundation of life on Earth".

Climate, economy, food, jobs, medicines: the irreplaceable role of the oceans

The World Ocean Assessment (WOA) was published on Monday 8 June. It is an extremely substantial document, running to 1,600 pages, that required years of work. It opens with a series of observations: the oceans cover 70 per cent of the planet's surface, regulate the climate, preserve biodiversity, and sustain economies and cultures the world over.

Without most of us even noticing, these enormous bodies of water affect our daily lives — even for those of us who do not live in coastal areas. It is thanks to the oceans that the pace of climate change is not even more pronounced, since they absorb a large share of the greenhouse gas emissions generated by human activities. They are also an extraordinary source of food. They produce a significant proportion of the oxygen we breathe. They support the production of certain medicines. They enable global trade worth trillions of dollars. And they generate jobs across numerous economic sectors.

Sea-level rise accelerated from 1.9 to 4.3 millimetres per year between 2015 and 2023

Protecting the oceans, therefore, means protecting ourselves. And yet, human activities in countless instances appear to ignore these realities. The United Nations report highlights how the intensification of natural resource exploitation, the development of infrastructure, the dumping of waste and the degradation of habitats caused by industrial, tourism and transport activities now represent constant threats — as well as profound alterations to ecosystems, from deep-water oil exploration to the pipelines installed in numerous parts of the world.

On top of all this comes the impact of climate change, which the WOA rates as "alarming". The rate of sea-level rise — driven by the melting of polar ice caps and the thermal expansion of water as average temperatures increase — has doubled in the very short span between 2015 and 2023, climbing from 1.9 millimetres to 4.3 millimetres per year. This is partly because climate warming in the Arctic region is proceeding far faster than the global average.

The multiplication of "dead zones" and the decline of biodiversity

The consequences for the oceans are multiple and alarming. The so-called "dead zones" — areas where oxygen levels fail to reach the minimum threshold needed to sustain marine life — now cover 4.5 million square kilometres. Some 80 per cent of coral reefs in the Caribbean region have disappeared since the 1970s. Should the rise in average global temperature exceed 1.5 degrees Celsius, it is estimated that 90 per cent of these irreplaceable natural structures will be destroyed worldwide.

Vital coastal ecosystems are also in retreat, including mangrove forests, which among other things help shield dry land from extreme weather events. Rising temperatures are also driving a migration of living species — from plankton to marine mammals — towards polar regions, while non-native species are spreading thanks to altered environmental conditions, reshaping and in some cases completely overturning habitats.

52 million tonnes of plastic waste enter the oceans every year

The United Nations report also recalls that every year 52 million tonnes of plastic waste are dumped into the world's oceans — so much so that an estimated 24,000 billion microplastic particles are now present in seas across the globe. A mass so vast that it has managed to contaminate four thousand marine species. Added to this are chemical compounds: more than four thousand substances derived from pharmaceutical and cosmetic products have been detected in the sea.

António Guterres ✓ @antonioguterres

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The ocean reminds us we are bound together. It shapes our climate, sustains ecosystems & economies, and feeds billions.

On World Ocean Day, let's act with ambition & resolve to build a new relationship with the ocean – grounded in science & build on shared responsibility.

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The weight of human activities is also measured through intensive fishing: in 2021, 37 per cent of fish stocks were subject to overexploitation. The report specifies that illegal fishing (i.e. unreported and unregulated) accounts for the removal of 8–14 million tonnes of fish from the seas each year, generating between 9 and 17 billion dollars in illicit revenues.

The economy revolving around the oceans is worth 1,500 billion dollars a year

But this represents only a small part of the economy that revolves around the oceans: their overall value is estimated at 1,500 billion dollars per year — a figure expected to double by 2030. Indeed, coastal and marine tourism alone supports 174 million jobs worldwide.

The problem, the United Nations report stresses, is that this economy is often not sustainable. Making it so requires taking into account a vast number of factors: not only environmental ones, but also, for example, "the knowledge and traditional practices of indigenous communities, without which it will be difficult to ensure the health of the oceans, human wellbeing and equitable development".

Some possible solutions: from scientific investment to ecosystem restoration

Scientific investment is also urgently needed: to date, seabed mapping has been completed for only 27 per cent of the ocean floor — a gap that translates into significant shortfalls in knowledge about ecosystems, biological processes and the overall impacts of human activities on the oceans.

Action can also be taken to restore degraded areas, reduce pollutants discharged into the sea, improve waste management, harness nature-based approaches and expand marine protected areas. According to the report, not all is lost — but "the next decade will be decisive: in the absence of rapid and coordinated global action, the health of the oceans will continue to deteriorate, threatening climate stability, biodiversity resilience, food security, livelihoods and the wellbeing of billions of people".