UPSTREAM/DOWNSTREAM and DEAD ZONES
Dead zones are places where the water is so depleted of oxygen that animals cannot live there. Human activity, in particular the application of nitrogen fertilizer to farmland, is the main cause of dead zones. In some bodies of water, the manure from confined animal feeding operations (CAFOs or factory farms) causes dead zones.
But the biggest problem comes from all the chemical fertilizers that run off of conventional farms in the Midwest, into rivers and streams, and eventually down the Mississippi to the Gulf of Mexico.
What are dead zones, and what causes them?
The contribution of animal agriculture to dead zones:
How climate change is making dead zones worse: