Dead zones are water-based habitats (oceans mostly, but also lakes and rivers), that would normally be teeming with life but instead are biological deserts as marine life cannot be supported any longer due to depleted oxygen levels caused by pollution. Dead zones occur around the world, but are primarily near areas where heavy agricultural and industrial activity spill nutrients into the water and compromise its quality accordingly. For the most part, dead zones exist because of us.
Perhaps the most well known dead zone is an 8,500 square mile are (an area larger than the entire country of Wales in the United Kingdom!) off the Gulf of Mexico, not far from where the Mississippi River lets out. This has had a huge negative impact on the once teeming shrimp industry and has led to reproductive problems for fish in general. According to The Guardian
, the cause of this enormous dead zone has now been entirely blamed on the global meat industry, an industry already widely know to have driven global warming and deforestation to crisis-levels.
A report by environmental group Mighty analysed supply chains of agribusiness and pollution trends. They found that a highly industrialised and centralized factory farm system was resulting in vast tracts of native grassland in the midwest being converted into soy and corn to feed livestock. Stripped soils can wash away in the rain, bringing fertilisers into waterways. The report identified Arkansas-based Tyson Foods as a dominant influence due to its market strength in chicken, beef and pork. Tyson, which supplies the likes of McDonald’s and Walmart, slaughters 35m chickens and 125,000 head of cattle every week (!), requiring five million acres of corn a year for feed, according to the report. This consumption resulted in Tyson generating 55m tons of manure last year, according to the Environmental Protection Agency (EPA), with 104m tons of pollutants dumped into waterways over the past decade.
This pollution has also been linked to drinking water contamination leading to consumption of nitrates that have been linked to an increased risk of contracting certain cancers. The Algal blooms themselves, the growth of which is stimulated by agriculture and wastewater, can also cause problems. In Florida last summer several beaches were closed after they became coated in foul-smelling green slime.
Fortunately, dead zones are reversible if their causes are reduced or eliminated. For example, a huge dead zone in the Black Sea largely disappeared in the 1990s following the fall of the Soviet Union, after which there was a huge spike in the cost of chemical fertilizers throughout the region. And while this situation was largely unintentional, the lessons learned have not been lost on scientists, policymakers and the United Nations, which has been pushing to reduce industrial emissions in other areas around the globe where dead zones are a problem.