Oceans, an essential but fragile element of life on Earth

If it’s a well-known fact that water was essential for the emergence of life on Earth, there is no doubt either that it plays an equally important role in maintaining that existence. In other words, by covering 71% of the Earth’s surface and containing 97% of its water resources, the world’s oceans are a determining factor for the environment. From the climate to habitats, and from food to transport, they are the focal point for a range of fundamental challenges facing the planet in the decades to come.

Published on 28 September 2022

Supported by the United Nations, the fifth edition of the One Planet Summit in Brest, France, in February of this year was devoted entirely to the oceans. A choice of subject that sent a strong signal, it came as little surprise to experts in the field. In 2015, the UN had set the preservation of “oceans, seas and marine resources” as its 14^th Sustainable Development Goal and awareness of their importance has been growing ever since. Determined to make protecting them a priority, the UN has declared the period from 2021-2030 “a decade of ocean science for sustainable development.”

Clearly, the sound of alarm bells ringing has become ever louder over time. Since the start of the Industrial Revolution, water pollution has led to a three-fold increase in the acidity of the world’s oceans, a life-changing phenomenon for many marine ecosystems. More visible is the fact that with between 4.8 million and 12.7 million tons of plastic ending up in the oceans every year, the Ellen MacArthur Foundation estimates that they could contain more plastic than fish by 2050¹. Already, 94% of northern sea birds are believed to have plastic in their stomachs². Meanwhile, after a record year for rising ocean temperatures in 2021³, a combination of the glacial melt occurring from Greenland to the Antarctic and the thermal expansion of seawater has led to a constant rise in sea levels.

The challenge is literally one of life or death. The source of life on Earth, the oceans also provide more than half of the oxygen we breathe. We are more dependent on phytoplankton – the minuscule plant organisms that are invisible to the naked eye, but live in suspension at the ocean surface⁴ – than we are on the Amazon rainforest. Phytoplankton produce oxygen, part of which is released into the water – helping sea creatures to breathe – and the rest is dispersed into the atmosphere. The problem is that their ability to do this depends on the water temperature⁵ – which has already risen by 0.76°C over the past century⁶. As a result, the oceans have lost 2% of their oxygen content over the last 50 years⁷.

The oceans are also one of our main allies for combating climate change, as they absorb between 20% and 30% of our CO2 emissions, along with 90% of the atmospheric warming caused by greenhouse gases. As they become warmer, saltier and more acidic, they also lose their ability to absorb CO2. The absorption capacity of the Southern Ocean as a carbon sink is now believed to be only a 10^th of previous estimations⁸. The melting of glaciers is an additional major source of concern, as their ability to reflect sunlight is another vital factor for our climate. More than 25 gigatons of ice have been lost since 1956, with half of that amount disappearing in the last 15 years⁹. Meanwhile, the surface area of pack ice has been reduced by 96% over the past 35 years¹⁰. Because of their ability to reflect the rays from the ground, glaciers are also a major contributor to our climate.

Human beings are directly affected by all these dangers. Currently, half of the world’s population live within 100 kilometres of a coastline. The IPCC report of September 2019¹¹ indicates that sea levels could rise by 1.1 to 2 metres in the coming decades — and that’s without including another phenomenon linked to global warming: the predicted increase in both the frequency and intensity of extreme weather events, storms and tsunamis.

Another issue is over-fishing. In 2018, world consumption of fish reached 20.5 kilos per person per year, according to the annual report of the UN’s Food and Agriculture Organization. In 1960, the world’s population, 3 billion at the time, consumed less than 10 kilos a year per head. Intensive fishing upsets the balance of ecosystems and degrades the seabed, while the exhaustion of such resources could have major repercussions for the global economy.

Fishing, aquaculture, coastal and marine tourism, research activities… around 350 million jobs worldwide are dependent on the so-called blue economy. In 2016, the Organisation for Economic Cooperation and Development¹² (OECD) estimated that it contributed $1.5 trillion to the global economy – a figure that is expected to double by 2030. It is also worth remembering that 90% of global trade is carried out by sea and that a cargo ship¹³ emits 100 times fewer greenhouse gases than a plane. What’s more, the first sail-powered cargo ships are now being introduced.

Seen from an ever-broader economic perspective, by combining areas such as fishing, transport and tourism, the world’s seas and oceans contain resources worth $24 trillion, creating $2.5 trillion in value a year: 32% through indirect production (tourism, coastal activities), 29% in direct production (fish, algae, coral reefs, deep sea/sea bed activities and mangrove swamps), 22% in maritime transport and 17% through their ecological impact¹⁴.

Lastly, a final key element in all this brings several different issues together: the oceans are also a source of energy, which is destined for exponential growth over the coming decades. The potential of offshore windfarms is far greater than those onshore. A report in 2019 by the International Energy Agency (IEA) estimates the offshore potential to be 420,000 TWh a year – a figure 18 times bigger than global demand for electricity. In Europe, the leader in the field, the potential for offshore energy exceeds 33,000 TWh, while electricity demand is less than 3,000 TWh.

Yet the energy potential of oceans goes far beyond wind power. Many technologies are currently being developed to provide sustainable energy, using different aspects of oceans (such as waves, tides, currents, and salt levels). Hydraulic turbines, barrages, wave installations and tidal power plants are all opportunities with real promise. As victims of climate change and, at the same time, a source of solutions to the problem, oceans are increasingly at the heart of the environmental challenge.