So-called ‘Dead Zones’ - oxygen-starved areas of the world's oceans that are devoid of life - top the list of emerging environmental crises facing our planet.

The spreading dead zones have doubled over the last decade, and pose as large a threat to world fish stocks as over fishing does.

The latest findings tally nearly 150 Dead Zones around the globe, doubling the number found in 1990.

Dead Zones have long afflicted the Gulf of Mexico and Chesapeake Bay, but are now spreading to other bodies of water, such as the Baltic Sea, the Black Sea, the Adriatic Sea, the Gulf of Thailand, and the Yellow Sea.

They are also appearing off South America, Japan, Australia, and New Zealand.

The main cause of these oceanic dead zones is excess nitrogen run-off from farm fertilizers, raw sewage discharges, and industrial pollutants.

The released nitrogen triggers blooms of microscopic algae known as phytoplankton. As this algae die and rot, they consume oxygen, thereby suffocating everything in the newly created Dead Zone, from clams and lobsters to oysters and fish.

"Human kind is engaged in a gigantic global experiment as a result of inefficient and often overuse of fertilizers, the discharge of untreated sewage, and the ever rising emissions from vehicles and factories," United Nations Environment Program (UNEP) Executive Director Klaus Toepfer said in a recent statement.  "Unless urgent action is taken soon to tackle the sources of the problem, it is likely to escalate rapidly," Toepfer said.

UNEP urged nations to cooperate in reducing the amount of nitrogen discharged into their coastal waters, in part by cutting back on fertilizer use and by planting more forests and grasslands along feeder rivers to soak up the excess nitrogen before it reaches the ocean.

Few nations have taken this task to heart.

The Dead Zone in the Gulf of Mexico has now spread across 5,800 miles and is killing all the marine life within it.

As a result, various adaptable predatory marine creatures are now seeking fresher water, and new food sources, and are suddenly coming much closer to shore.

This may explain the increase of unprovoked shark attacks on swimmers in the last several years.

On the Texas coast alone, numerous shark attacks have recently occurred, whereas over the previous 24 years, only 18 total attacks took place – less than one a year.

Almost nothing is currently being done to stop the flow of nitrates into the seas.

We are now quickly killing all of our oceans, and this should fill no one with glee.

And be extremely careful swimming at your favorite ocean beach these days; sharks have survived for millions of years, by skillfully learning how to adapt in numerous ways.