What Is the 'Dead Zone' in the Gulf of Mexico?

Complacent methods of modern agriculture have combined with climate change and improper waste disposal to create a huge oxygen-starved stretch of water in the Gulf of Mexico, known colloquially as the “dead zone”.

Although the Gulf of Mexico site is the largest in the world, there are believed to be in excess of 500 other similarly oxygen-deprived coastal locations across the globe. The phenomenon is caused primarily by fertilisers from agricultural activity finding their way into rivers and seas, and poses a significant threat to the marine life living there.

A long way back

The Gulf of Mexico’s dead zone is now believed to be over 8,200 square miles in size, meaning it’s bigger than the whole of Wales. That’s the largest it’s ever been, and a new study published in the journal Science shows that even if all leeching of nitrogen (a chemical often used in agricultural fertilizers) into the waters was stopped, it would still take decades to recover.

Such a scenario is not only entirely unfeasible, it also would result in the Gulf of Mexico taking as many as 30 years to return to its previous state of health. Meanwhile, the location is far from alone. In 1950, there were a mere 50 documented cases of global waters suffering from hypoxia (oxygen deprivation); in 2015, there were at least 500.

Overambitious targets

In 2008, the US Environmental Protection Agency put forward a plan to reduce the size of the Gulf of Mexico dead zone to under 2,000 square miles by 2015. However, when the deadline rolled around, the zone was over three times bigger than the target, forcing the EPA to revise their date to 2035.

A smaller milestone goal outlined in the same plan was to reduce the amount of nitrogen leeching into the Gulf via the Mississippi River by 20% before 2025, which could be achieved through use of digestate as an organic fertiliser, increased responsibility in the use of chemical fertilisers, the planting of fringe grasses to act as pollutant filters and the adoption of minimum tillage, which reduces the chance of soil degradation. Unfortunately, however, it doesn’t look like the EPA will even meet its interim goal.

Little by little

In order to reduce the frequency and size of dead zones like the one found in the Gulf of Mexico, it is necessary for the global farming community to reduce pollution via more environmentally-friendly methods of agriculture, such as those mentioned above. However, even if this sea change is realised, the Science study shows that the beneficial effects will not be visible for some time yet.

“We have been building up nitrogen for the past 50 years and it will take time to go through the system,” explained Nandita Basu, a co-author on the study. “Money is being spent on the landscape in an ad hoc way. We need to focus better. If we make the right changes it will have an impact, it’s just that it’ll take a few decades. It’s like when you go on a diet – you can’t expect results right away.”