The math on why this dead zone persists is the real story. Corn gets $3.2 billion per year in federal subsidies. The Renewable Fuel Standard mandates that ~15 billion gallons of ethanol get blended into gasoline annually. 40% of all US corn goes to ethanol facilities. The entire chain, from fertilizer to runoff to algae bloom to oxygen collapse, is federally underwritten. The dead zone causes $2.4 billion in annual damage to Gulf fisheries and marine habitat. The brown shrimp fishery, once the most valuable in America, has been in decline for decades. Louisiana shrimpers catch smaller shrimp from shallower water because the oxygen-depleted zone pushes the population inshore. Smaller shrimp sell for less. The Gulf fishing industry generates $57 billion in economic activity and 200,000 jobs. Here's the structural lock. Iowa hosts the first presidential caucus. Corn subsidy votes happen in the Farm Bill. The Farm Bill gets reauthorized every five years by the same legislators who need Iowa. The people paying the cost of the nitrogen runoff, Gulf shrimpers in Louisiana and Texas, have no seat at the table where fertilizer policy gets written. The externality isn't 8,776 square miles. The externality is a policy choice that gets renewed every five years because the beneficiaries and the victims are in different states with different political leverage.