This is the fourth installment in “Growing Concern,” an occasional series about how issues related to growth threaten Chesapeake restoration efforts.
The Chesapeake may be on a “pollution diet,” but one of the most effective ways to make the Bay healthy might be to put watershed residents on a diet as well, according to a number of scientists.
The Bay, they say, is a reflection of what we eat.
The so-called Chesapeake pollution diet, or Total Maximum Daily Load, is aimed at trimming the amount of nitrogen and phosphorus that enters the estuary, where they spur the growth of huge algae blooms that foul the Bay’s water.
Fertilizers and animal waste running off farms is the largest single source of those nutrients, both to the Bay and many other coastal waters, spurring new, and often controversial attempts, to crack down on agriculture.
Part of the reason the Bay is bloated, though, stems from consumer food choices. In recent decades, the populations of the United States and most other developed countries have moved toward protein-rich diets that require disproportionately large amounts of nitrogen to produce. That inevitably means that more nitrogen leaks into the environment, often making it into waterways.
“People think of the person putting out the nitrogen as being the problem, but [that person is] doing it to meet a demand,” said Richard Kohn, an expert on animal nutrient management with the University of Maryland. “Farmers are producing food because people are eating it.”
In addition, people waste huge amounts of food. More than a third of all food produced in the United States is never eaten: It is simply thrown away, spoils or is otherwise unusable, according to the U.S. Department of Agriculture.
The influence food consumption has on nitrogen pollution was highlighted recently by an international team of scientists who developed a calculator that allows individuals to estimate their nitrogen “footprint” – the amount of nitrogen that is released into the environment as a result of decisions they make about eating, driving, electricity use and other factors.
The average American’s nitrogen “footprint” is 92 pounds a year, according to their N-PRINT calculator. A whopping 72 percent of that stems from what they eat.
As a result, altering one’s diet can be the most effective way to for individuals to reduce their footprint.
“This is not that difficult a problem,” said Jim Galloway, Sidman Poole Professor of Environmental Science at the University of Virginia, and one of the leading experts on the nitrogen cycle. He helped develop the calculator with Kohn and others. “If people did two things – ate to the protein guidelines that we’re supposed to and really decreased their food waste – then you are talking about a substantial decrease in the amount of nitrogen needed to come into an agricultural system.”
If someone eating an average U.S. diet instead ate the amount of protein recommended by the Institute of Medicine and the World Health Organization, they would slash the food portion of their nitrogen footprint by about 42 percent, according to the N-PRINT calculator. If they followed those guidelines and also cut food waste by half, they would reduce the food-related portion of their footprint by 50 percent.
Like other individual actions, if adopted on a wide scale, the change could make a big difference. A 2002 paper that Galloway co-authored suggested that if Americans adopted a Swedish-style diet, which has about half the meat consumption of the U.S. diet, fertilizer use would decrease 37 percent. If Americans were persuaded to adopt the Mediterranean diet, which has only about a fifth of the meat of a typical U.S. diet, fertilizer use would decrease by more than half. That would, in effect, return fertilizer use rates roughly to where they were in the 1960s, when the Bay was relatively healthy.