Perhaps you've heard about the giant dead zone in the Gulf of Mexico. Do you know it why it's there?
According to a research paper by MightyEarth.org the main cause is chemical fertiliser and manure pollution from factory farms and animal feed crops, primarily corn and soy. Polluted run-off flows into the Mississippi River and ends up in the Gulf of Mexico. This nitrogen and phosphorus rich fertiliser and manure causes algae blooms, which is toxic to marine life (and humans), and ultimately causes dead zones.
According to the research,
Approximately 1.15 million metric tons of nitrogen pollution flowed into the Gulf of Mexico in 2016 alone, which is around 170 percent more pollution than was dumped into the Gulf by the BP oil spill.