‘The High Seas’ tells of the many ways humans are laying claim to the ocean

Conservation goals often coexist alongside increased exploration and exploitation

Aerial photo of a salmon fish farm in Bergen, Norway

One pressure on international waters is the search for new sources of fish to support aquaculture (a salmon farm in Norway is shown).

MariusLtu/Getty Images Plus

The High Seas
Olive Heffernan
Greystone Books, $32.95

The ocean is a rich, fertile and seemingly lawless frontier. It’s a watery wild west, irresistible to humans hoping to plunder its many riches.

That is the narrative throughout The High Seas: Greed, Power and the Battle for the Unclaimed Ocean, a fast-paced, thoroughly reported and deeply disquieting book by science journalist Olive Heffernan, also the founding chief editor of the journal Nature Climate Change.

The book begins by churning rapidly through the waves of history that brought us to today, including how we even define the high seas: all ocean waters more than 200 nautical miles from any country’s coastline. In many ways, the modern ocean grab was set in motion some 400 years ago. A bitter feud between Dutch and Portuguese traders culminated in a legal document called the Mare Liberum, or the “free seas,” which argues that the ocean is a vast global commons owned by no one.

Heffernan devotes a chapter each to different ways people are increasingly staking claims to international waters, an expansion called the Blue Acceleration. Some are hunting for new fishing grounds or prospecting for seafloor ores (SN: 5/4/20). Others are searching for new medicines in the DNA of deep-sea microbes, sponges or sea lilies. Still others are exploring how to boost the ocean’s carbon uptake to help slow climate change (SN: 4/26/24). Even the space industry wants a piece of the ocean — to create watery graveyards for defunct spacecraft.

The careening from one ocean ambition to another underscores one of the book’s biggest takeaways: We’ve established a precarious new type of ocean ecosystem, and it is going to be incredibly difficult — maybe impossible — to juggle all the priorities while also protecting ocean health and biodiversity.

Consider Trondheim, Norway, where Heffernan visits the SINTEF SeaLab. One of the world’s wealthiest oil states, Norway wants to move its economy away from oil and more toward aquaculture, partly by dramatically increasing the production of its coastal salmon farms. The ocean’s twilight zone, the murky waters that extend from about 100 meters to 1,000 meters below the surface, where sunlight no longer penetrates, could provide an immense untapped resource of feeder fish for those farmed salmon. By at least one estimate, Heffernan writes, the twilight zone contains as much as 95 percent of the ocean’s fish by weight.

But these twilight denizens are also key to the ocean’s ability to sequester atmospheric carbon (SN: 11/28/17). Crustaceans, fish and other creatures rise toward the surface to feed on carbon-bearing plankton at night, and then sink into the depths during the day — carrying that carbon into the deep.

Such conflicting desires to plunder and protect show up over and over again. Nations urging conservation in one arena may push for increasing exploration or exploitation in another, Heffernan writes. The European Union in 2021, for example, offered subsidies to its fishing fleet to range farther offshore, even as it committed to sustainable fishing. Nations keen to commit to protecting marine life and combating climate change may be the same countries that support deep-sea mining, which may be detrimental to life on the ocean floor.

The problem, Heffernan says, isn’t that the high seas are without any rules. Rather, there’s “a mishmash of organizations and bodies, each using their own rulebook.” Plus, she adds, “I now realize that many of those tasked with governing this space willfully ignore science and disregard expert advice.”

There are global efforts afoot to establish uniform, consistent regulations on ocean activities. In particular, Heffernan notes that in 2023, United Nations member states passed the High Seas Treaty, which would establish marine protected areas in international waters. If ratified, the treaty could be a big step toward conserving ocean biodiversity.

But be warned: This is not an uplifting book. By the final chapter — titled, somewhat unconvincingly, “Hope for the high seas” — it’s hard to know what anyone could actually do to help save the ocean. What The High Seas does, and powerfully, is convey the sheer scope and complexity of the Blue Acceleration. We’re at a crucial juncture, Heffernan writes: “We can continue going ever deeper and further offshore in our quest for new sources of wealth, or we can strike a more sustainable balance.”

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Carolyn Gramling is the earth & climate writer. She has bachelor’s degrees in geology and European history and a Ph.D. in marine geochemistry from MIT and the Woods Hole Oceanographic Institution.

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