1. Reads
  2. Lite

What Are Ocean Dead Zones?

Professor of Financial Economics and Part-time Value Investor, Transfin.
Jan 27, 2020 10:07 AM 2 min read

The sea. Windy, calming, exhilarating. Even a brief visit to the beach can reinvigorate you with new life.


Sadly, the same cannot be said for life that lives in - or depends on - the sea.


Hold Your Breath: Dead zones are regions in the world's oceans, lakes and rivers where oxygen levels are too low ("hypoxic") for aquatic life to survive. Before the 1970s, most of these zones were naturally-occurring. But since then, studies have documented a spike in their occurrence. In fact, scientists estimate the size of ocean dead zones has quadruped since the mid-20th century. This is due to an increase in influx of chemical nutrients (from human pollution) that spurs algae growth, which in turn sucks up oxygen.


What Are Ocean Dead Zones?


The State of Affairs: Here's a map of the world's dead zones. It's damning. You see these zones in bits and spots along North America, Europe, China - but it is when you come to India that the extent of the devastation drives home. The entirety of the Arabian Sea and Bay of Bengal is a vast dead zone - the entire Indian peninsula is surrounded on all sides by oxygen-deprived water unfit for marine life.


As oxygen levels in oceans fall due to pollution and climate change, entire species are on the brink of endangerment or extinction. Besides the threat to biodiversity, the proliferation of dead zones poses an existential threat to marine and coastal economies, which stand to lose important fishing grounds and sources of livelihood.


Careful By Accident: Thankfully, dead zones are reversible - reducing sewage and industrial emissions into the sea does the trick. But there's little policy impetus in that direction. In fact, the most successful example of re-oxygenating oceans was completely unintentional. The Black Sea dead zone largely disappeared in the 1990s - because chemical fertilizers became too costly following the fall of the Soviet Union.


(Want to read about ocean pollution and what the world is doing to reverse it? Click here for a deep-dive.)


How well do you know the top news of the last week? Have a go at our TheWeekThatWas Quiz and test your wits.