It’s understandable that, when it comes to the oceans, we mainly think about what’s happening up at the surface. Grim stories of the epic scale of plastic pollution often dominate the headlines, particularly when the world seems to react too slowly, or too feebly, to the crisis at hand.
A new, comprehensive review in the journal Science has pointed out, in no uncertain terms, that another catastrophe is unfolding deep below those blue crests and troughs. Our oceans are being somewhat suffocated by our behavior; its deep reserves of oxygen are disappearing at a breakneck speed, and Earth's biosphere will soon begin to suffer the consequences if nothing is done to reverse the trend.
The study concludes by suggesting that, “in the longer term, these conditions are unsustainable and may result in ecosystem collapses, which ultimately will cause societal and economic harm.”
The review, the largest of its kind, was led by an enormous international team of researchers collectively known as the Global Ocean Oxygen Network, or GO2NE. It makes for an unquestionably upsetting read.
The study notes that oxygen concentrations in large swaths of the ocean – including both the wide expanse far from land, and along coastal regions – has declined precipitously since the 1950s.
Oxygen-minimum zones, sometimes referred to as “dead zones”, aren’t a new phenomenon; they've been around for hundreds of millions of years. However, today, they’re proliferating and expanding rapidly, and they aren't being driven by natural processes.
Since the middle of the 20th century, those in the open ocean have quadrupled in size, whereas those along the coast have experienced a 10 times increase.
To put it another way, the open ocean oxygen minimum dead zones have expanded in size by 4.5 million square kilometers (1.7 million square miles), which the authors compares to “the size of the European Union.” That is roughly 46 percent of the area of the US, or 18.5 times the size of the UK.
It's worth pointing out, as the new study does, that oxygen-deficient oceans in warmer climates are often associated with major extinction events. Previous studies have noted that the sudden appearance of dead zones within the oceans – sometimes called anoxic events – devastated life in the Cretaceous Period. One naturally-occurring event back then killed off 27 percent of all marine invertebrates.
Although there are plenty of extremophiles in the oceans that can live perfectly happily without oxygen, it’s a necessity for a plethora of life. Without it, they die, food chains collapse, and – considering how much humanity relies on the oceans – we will pay a price too high to handle.