What are the high seas?

High seas or international waters? Where do the high seas begin? Who do they belong to? Why are they important for mankind?

haute mer

Let's try to learn a little more about the high seas, which make up half of the world's surface.

First of all, what are the high seas? and where do they begin?

The high seas are the maritime area that lies beyond the areas under the jurisdiction of States.

Territorial waters extend from the baseline to 12 nautical miles (1 nautical mile = 1.852 km)

Beyond that and up to 200 miles (370 km) lies the EEZ or Exclusive Economic Zone. In this maritime space, the coastal state may exploit and use the water, seabed and substratum resources as it sees fit.

  • The high seas form the international waters.
  • They belong to no one and are the responsibility of everyone!
  • The high seas take up half of the world's surface and account for 65% of the surface area of the oceans and 90% of their volume.

In the high seas, a distinction is made between the water column and the seabed, called the Zone, which includes the seabed and substratum. The resources in the Zone are considered to be the common heritage of mankind. The International Seabed Authority (ISA) regulates exploration and mining while maintaining environmental protection.

Did you know? France has the second largest maritime domain in the world, after the United States. This represents more than 10.2 million km² owing to the overseas territories (French Polynesia, New Caledonia, Southern and Antarctic Territories).

where are the high seas ?

What is the status of the high seas?

If the high seas do not belong to anyone, are there any regulations? Any governance? Or is it the "wild west" in the open ocean?

The high seas are an area common to all the countries of the world. No one can claim it or exercise sovereignty over it.

It is the principle of freedom of the seas that applies to the high seas.

This provides:

  • freedom to navigate,
  • freedom to fly over,
  • freedom to lay submarine cables and pipelines,
  • the creation of artificial islands permitted under international law,
  • freedom to fish and conduct scientific research.

However, the first UN Conference on the Law of the Sea was held in Geneva in 1958. Several conventions have been adopted in order to establish an international treaty regulating maritime affairs and the competences of States over maritime spaces.

This treaty is the Montego Bay Convention on the Law of the Sea adopted in 1982. It entered into force in 1994 and has since been ratified by 168 signatory states including France in 1996. This convention contains the principle of the Exclusive Economic Zone.

Why is there such an interest in the high seas?

Beyond the economic potential of the high seas, for example, the high seas are essential to life on Earth because they are the basis of planetary equilibrium.

Without the ocean, life would not be possible. Everything is connected: the ocean, the atmosphere and the land.

Cycle de l'eau  en infographie par la Plateforme Océan & Climat (POC)
Cycle de l'eau par la Plateforme Océan & Climat (POC)
  • Living things depend on the ocean for climate regulation and the water cycle.
  • The ocean produces more than 50% of the oxygen we breathe.
  • It stores more than 90% of the excess heat caused by global warming due to human activities.
Pompe à carbone physique en infographie
Pompe à carbone physique
  • It stores more than 90% of the excess heat caused by global warming due to human activities.
  • 25% of carbon dioxide from human activities is absorbed by the ocean. Phytoplankton contribute to CO2 absorption.
  • Carbon is stored and deposited on the ocean floor, accumulating in the sediments.
  • Phytoplankton contribute to CO2 absorption. Carbon is stored and deposited on the ocean floor, accumulating in the sediments.
  • The ocean provides invaluable services through the human activities that can be developed in it, such as fishing, freight transport and communications through submarine cables.

The ocean is the primary source of protein for 3 billion people and 90% of freight reaches us by sea!

What lies beneath the surface of the high seas?

This lack of knowledge does not mean that it is not coveted, as the potential of the high seas is immense: such as living resources, mineral resources, new molecules.


what we know on the high seas

We know more about the surface of the Moon than we do about the seabed!

Even if it is clearly understood that the ocean's resources are not infinite, the IUCN estimates that there are between 500,000 and 100 million species living in the oceans and only about 250,000 species have been recorded.

Moreover, the deep sea, such as the abyssal plains or the deep ocean trenches, are extreme places where marine life can nevertheless thrive, particularly around hydrothermal vents, where temperatures can reach 400 degrees.

The ability of species to adapt is a clear indication of the immense biological diversity that exists in the high seas.

By 2030, the Organisation for Economic Co-operation and Development (OECD) predicts that profits generated at sea will exceed those generated on land.

What is the potential of the high seas?

  • The high seas are used for fishing, for transporting 90% of international trade, and for laying the submarine cables through which our telephone and Internet communications pass.
  • Engineers seek to harness the tremendous power of waves and currents to provide clean, renewable energy.
  • The deep seabed is home to minerals and rare earths that are essential to our technologies and are already being explored.
  • The aim of the biodiversity census is to discover new molecules that will be the source of medicines and innovation, particularly in the chemical industry. The number of patents derived from marine genetic resources is substantially increasing.

Why do we need to protect the high seas?

The challenge of this century is to preserve biodiversity and natural balances in the high seas. Negotiations on the protection of biodiversity in maritime areas beyond national jurisdiction have been ongoing at the United Nations since 2018.

The 4th round of negotiations will take place in New York from the 7th to the 18th of March 2022.

What is at stake? The ocean's resources are not infinite and this wealth needs to be preserved and exploited ethically, sustainably and fairly.

The high seas are affected by human activities: overfishing, pollution, particularly from microplastics, and climate change are causing imbalances in marine ecosystems.

Plastic waste has been found in the Mariana Trench at a depth of 11,000 metres!

Activities on land have an impact on the ocean and the high seas. So how can the high seas be managed sustainably, with everybody's contribution?

Healthy high seas are vital to human societies.

The Ocean Magazine

banc de mérous ile de malpelo

A treaty on biodiversity in the high sea...

High Seas 6mn

More than 80 states gathered at the United Nations in New Yo...

Biodiversity in the open sea: from the s...

Biodiversity 8mn

Off the coast, beyond the territorial waters, lies the high ...

What is the water column?

High Seas 3mn

What lies beneath the surface of the ocean?