Scientists at Oxford University in the United Kingdom reviewed 271 research papers published between 2012 and 2017 and synthesized the latest data on the impact of climate change, fishing and pollution on the high seas. Their findings are not encouraging: Even the most distant reaches of the ocean are suffering from chemical and plastic contamination, a loss of biodiversity and the consequences of rising temperatures.
“There is mounting evidence that some regions are almost at an ecological tipping point,” the report’s authors wrote, stressing the high seas’ role in regulating global climate and coastal ecosystems. “An example of interactions between different human stressors is the recent discovery of a geochemical tipping point in the Bay of Bengal where further increases in runoff of agricultural fertilizers or further environmental changes caused by climate change could create a new extreme oxygen depleted zone.”
They added, “The consequences of this would be an impact on the global nitrogen cycle and large-scale disturbance of ecosystems in the Bay of Bengal, a region with high dependency on fishing for livelihoods and food security.”
The scientists conducted the review for the High Seas Alliance – a coalition of 32 major environmental groups, including the Natural Resources Defense Council, the World Wildlife Fund, Oceana and the Nature Conservancy, with the International Union for Conservation of Nature. The Alliance was founded in 2011 to advocate for the protection of the high seas.
The high seas comprise the 58 percent of the ocean beyond national jurisdiction and are largely unregulated. (The international high seas treaty under discussion at the U.N. would allow the creation of marine protected areas and other measures to preserve marine biodiversity.) By definition, the high seas are far-flung and have been little studied due to the high cost and technological challenges of exploration, particularly in the deep ocean where depths are measured in miles.
For instance, there are an estimated 170,000 underwater mountains – called seamounts – in the ocean, but only 250–280 have been sampled for their biological diversity, according to the study. Seamounts are rich in valuable minerals and have drawn the interest of countries and corporations that plan to mine them. Those seamounts that have been explored have been found to be home to unique marine species, the researchers said.
Still, advances in autonomous submersible vehicles, sensors and other technologies have extended scientists’ understanding of the potential impacts on high-sea ecosystems from human activities.
“We can now recognize that the ocean is far more complex and diverse than we had assumed,” Lucy Woodall, a marine biologist and a coauthor of the report, said on Tuesday at the U.N.
Miners are also interested in deposits of gold, copper and rare earth metals found around hydrothermal vents on the seabed. “Active hydrothermal vents host a fauna that is typified by highly specialised animals not found elsewhere,” the authors wrote. “It has been estimated [that] at least 11 different types of communities have been found on them globally, with new types of animal communities still being found.
“Biodiversity loss is inevitable” from mining, they added.
The report also noted that scientists have recently discovered deep-sea sponges in the East China Sea thought to be 11,000 years old and deep-sea corals estimated to be 4,000 years old. “Extreme longevity in such organisms is coupled with extremely low growth rates, which are related to low food supply in the deep ocean,” wrote Woodall and her coauthors. “This renders populations of such organisms slow to recover from disturbances such as the impacts of deep-sea trawling.
“The sparsity of knowledge about the life history of deep-sea species, even those that are economically important … makes the management of deep-sea fishing ineffective,” they added.
In other words, human impacts on the high seas are outstripping scientists’ ability to discover and catalog what is being lost.
“This review demonstrates that there is more than enough evidence that the high seas are a vital part of whole ocean health and need rigorous protection to ensure that they can continue performing vital ecosystem services of benefit to our planet,” report coauthor Alex Rogers said in a statement. “The scientific challenge is now to work with more speed, scale and coordination to be able to model the potential changes due to climate change and other human-made influences which will undoubtedly affect us all.”