June 21st, 2019

Have you heard the term ‘High Seas’, blinked, perhaps nodded, and continued about your day none-the-wiser as to what those two – relatively small, simple – words actually mean in combination? It’s one of those terms that crops up in the marine world, and means a whole lot more than you’d expect. Sophie Manson explains.



It is no secret that the ocean is enormous. It covers 70% of the Earth, yet we’ve barely scratched its surface. Its size and inaccessibility has made it difficult to explore and, equally, difficult to regulate. Countries have sovereign rights to (explore, exploit, conserve, and manage) the natural resources found within the waters that lie within 200 nautical miles of their coastline, and beyond this invisible line lies the High Seas. They’re a completely different kettle of fish.


📷: Nina Constable

📷: Nina Constable


Right now, the High Seas are having a bit of a moment – a hugely important series of international negotiations are due to conclude next year, which will determine how we, the human species, manage everything that lies beyond national waters: fish, shipping lanes, the seabed, mineral resources and more.

Just imagine how complex that is. Well, we’re here to de-mystify – so let’s start with a few key terms.

  • EEZ (Exclusive Economic Zone): The waters to which a country or state has sovereign rights – i.e. the waters that are within 200 nautical miles of their coastline

  • ABNJ (Areas Beyond National Jurisdiction): Any waters that edge over that 200 nautical mile mark (basically another term for ‘High Seas’)

  • BBNJ (Biodiversity Beyond National Jurisdiction): Any plant or animal life living in the High Seas, meaning that their welfare is not any single country’s responsibility

  • Legally binding instrument: A fancy term for an agreement that has to be legally upheld by every country that signs it – in this instance, the term ‘treaty’ is also often used

  • RFMOs (Regional Fisheries Management Organisations): International Organisations formed by countries with a shared interest in fishing a certain area or certain species in waters outside national jurisdiction

  • IOTC (Indian Ocean Tuna Commission): An RFMO managing High Seas tuna fishing in the Indian Ocean


Hear the words ‘High Seas’ and immediately start thinking pirates and ghost ships? Rightly so. The phrase originated in the 14th century, a time when little was known of the ocean except for the wild tales that were told by sailors and merchants.


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The High Seas are the waters that do not fall within the EEZ of any country. In other words, they are not ‘owned’ or governed by a particular state. Instead, they are ‘owned’ by everybody, the ‘Common Heritage of Humankind’.

With the High Seas covering around 50% of the Earth’s surface, we need to re-evaluate our behaviour in these zones – it is having far more of an effect on coastal communities and marine life than we once thought.


The short answer? Since 2018, the UN has been holding negotiations to agree a legally-binding treaty between all countries in the world and decide how we can better manage the High Seas.

But the full answer goes back further than that. Over the past few centuries, the pressures we have put on the oceans have changed big time. As human populations have grown, so have demands for food, and so has food production – including fishing. Because there is no overarching law for the High Seas, there is no legal imperative to fish sustainably there. We’ve also started to exhaust mineral resources on land, and mining companies are looking to the seabed for the next generation of key ‘rare earth’ deposits. But what does drilling into the seabed mean for marine life?


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In 2001, scientists gathered the first images of deep-sea, cold-water corals. In examining the images, they saw instances where these slow-growing corals had been damaged by deep-sea fishing.These were things we didn’t even know existed, and yet, somehow, our first sight of them was corrupted. Our ever-growing understanding of this seascape began to change as we learned more about the interconnectivity of the oceans and the massive impact our behaviour can have across the whole ocean. It became clear that an area that once seemed impossibly vast – too big to damage – was not beyond the reach of human impacts.

Recent studies have also shown a direct link between the High Seas and coastal communities. For example, when pollutants are dumped in the deepest, darkest depths of the Indian Ocean, they eventually find their way to the coastlines of countries like Tanzania and Kiribati.


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The cruel twist of fate here is that the more affluent nations dumping the pollution are not those most affected by their actions. Instead, developing countries that rely more heavily on the ocean for food, health and employment, are disproportionately affected.

This has all ultimately sparked a change in our approach to the High Seas. Instead of seeing them as an unmanageable desert, we are increasingly coming to realise that they are something we all depend on.

Bringing them ‘closer to home’ and showing their relevance across the world is exactly what we need to start seeing meaningful action – and something the UN treaty (and this article!) hope to achieve.



The UN wants to ensure that humankind is protecting and conserving life within the High Seas while safeguarding the livelihoods of people living in threatened coastal communities.

In order to do this, all uses of the High Seas will have to be discussed and addressed, including fisheries management, biodiversity protection, shipping, deep-sea mining and resource rights. By creating legal mandates to manage these areas, it will not only preserve the High Seas but will also benefit the management of the oceans as a whole.

Not to be a party pooper, but this is hugely challenging and requires well over 150 countries to work together. And we all know how easy it is to get just one government on the same page(!).

Ultimately, the goal is to get the world’s governments to agree to a legally binding agreement – where ‘legally binding’ basically means we are legally obliging ourselves to not trash the High Seas. Crucially, this ‘instrument’ is a ‘package deal’ so in agreeing on measures to cover marine protection, nations would also agree to protocols for deep-sea mining, sharing ocean genetic resources and so on.


The Intergovernmental Conference on the Sustainable Use of Marine Biodiversity (the group of nations negotiating the treaty/legally binding instrument),  is now headed towards their third session which is being held this July. Alongside world-leading researchers and dedicated organisations, national representatives will discuss key issues surrounding the sustainability of the High Seas and learn about the wide-reaching effects of its misuse.

The UN’s High Seas Treaty is due to be agreed in 2020.


#OurPlanet is narrated by David Attenborough and available on Netflix in collaboration with WWF. We highly recommend the ‘High Seas’ episode!

#OurPlanet is narrated by David Attenborough and available on Netflix in collaboration with WWF. We highly recommend the ‘High Seas’ episode!


This is a huge international undertaking, requiring a vast array of nations to work meaningfully together. Conflicting beliefs, economic priorities and cultural differences will no doubt be difficult to navigate as the treaty heads into its final stages.

There are so many issues to be resolved, and we could list a dozen, but to give you a sense of some of the key hurdles to overcome here are our top three stumbling blocks:

📷: Nina Constable

📷: Nina Constable


  • Representation: How can we ensure landlocked and small, developing countries have their voices heard?

  • Meaningful protection: How will High Seas marine protected areas (MPAs) be managed and enforced, and where will the resources come from to ensure they’re not simply ‘paper parks’?

  • Subsidies: Will international governments continue to subsidise fishing on the High Seas? Subsidies add as much as 25% to the profit margins of some High Seas vessels’ operations.

We’re not going to lie, it’s tricky stuff.


With several Sustainable Development Goal 14 targets due to be met and the High Seas Treaty set to be finalised, 2020 is shaping up to be a huge year for the oceans. And, kicking off the UN’s Decade of Ocean Science from 2021-2030, that’s just the beginning.

It’s not all in the hands of world leaders – whether you choose to read the entirety of UNCLOS (United Nations Convention on the Law of the Sea) or curl up on your sofa and watch the ‘High Seas’ episode of Our Planet (available on Netflix in collaboration with WWF), teaching yourself more about these vast and vital areas of the world is key to social change.

Follow @MWCMarine on Twitter to keep up to date on all things sustainability, and remember, in the words of our hero Greta Thunberg, ‘no one is too small to make a difference’.

For more information on this visit the High Seas Alliance blog, and keep your eyes out for a report coming from us soon.



Have a question about the #HighSeas or want to share your thoughts with us? Let us know:

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