In many ways, unfortunately, the Chesapeake Bay is ground zero when looking at the environmental impact of our food production. Inundated by pollution from factory farms, as well as sewage treatment plants, vehicle exhaust and power plant emissions, the Bay’s reputation as a high quality source of crabs and seafood has suffered over the years.

As chicken replaced beef as the number once source of protein on American dinner plates, the number of chickens crammed into factory farms—agricultural operations raising chickens and other farm animals on an industrial scale—has skyrocketed.  According to Food & Water Watch, Maryland has six factory-farmed broiler chickens (those raised for meat, not eggs) for every one person in the state. Think that’s a lot? Delaware has 19 factory-farmed broiler chickens for every human resident of the state.

The pollution from these facilities has been especially difficult to control.  The chicken manure and their bedding is dried in large piles and then spread as fertilizer on nearby farm fields.  Unfortunately, the amount of waste far exceeds the capacity of the crops to absorb the nutrients, and every time it rains the excess runs off the fields into nearby streams and then flows into the Chesapeake Bay.

According to the Chesapeake Bay Foundation, the runoff from farm fields accounts for 40 percent of the nitrogen and 50 percent of the phosphorous entering the Bay. As the key nutrients in fertilizer, nitrogen and phosphorous promote plant growth everywhere—and in water, this means the growth of algae blooms that consume the oxygen in the water.

In centuries past, marine species known as “filter feeders” would consume the algae and other types of plankton, keeping the water clean.  These filter feeders include well-known species such as oysters and mostly unknown species such as Atlantic menhaden.  But while the runoff from factory farms has vastly increased the amount of food for the filter feeders, overfishing has decimated their populations.

Atlantic menhaden, for example, once existed in vast quantities so large that schools once stretched for dozens of miles. A small innocuous fish no more than a foot in length, it can eat the algae in more than four gallons of water every minute.  Menhaden are the food of choice for seabirds, whales and marine mammals, and predator fish like the striped bass, blue fish, bluefin tuna, king mackerel, and Atlantic tarpon.

Read the full article at National Geographic News Watch.

Analysis: Contray to the article's assertions, menhaden are currently not considered to be overfished. There is also no consistent pattern of overfishing; in the last ten years, menhaden have been overfished only once, while the stock remains at its target abundance level.

There is also a considerable body of scientific literature, including the study by the Virginia Institute of Marine Science cited in the article, that menhaden contribute little to overall water quality, and adult menhaden do not filter a significant amount of the phytoplankton that contributes to water problems in the Bay.