Perhaps you’ve installed a rain barrel and started carpooling to work a few days a week to reduce the amount of pollution you’re contributing to the Chesapeake Bay. But have you considered the amount of meat you eat?

According to a new, improved nitrogen calculator released recently by the Chesapeake Bay Foundation, eating meat is responsible for more of the pollutant getting into the water than any other lifestyle factors, including the size of a person’s home, energy or water consumption or how one gets around.

The environmental group worked with the University of Virginia to add the impact of a person’s food choices to its Bay Footprint calculator, which applies the concept of a carbon footprint to one of the Chesapeake’s main pollutants, nitrogen.

Now, what people eat — and particularly how much protein they consume — is often the biggest way they impact the Bay environment, according to the calculator.

“People think the Bay restoration is all about agriculture or industry or new development, but it’s also about our individual actions,” said Beth McGee, director of science and agricultural policy at the Bay Foundation. “This is a way to quantify the benefits if they choose to change their behavior in a way that’s better for the environment.”

The idea that eating less meat could be a boon for the Bay is still a relatively new concept for many. An international team of scientists developed the first nitrogen “footprint” calculator a few years ago, which allows individuals in various countries to calculate their impact on water quality based on how they eat, drive, use electricity and other factors. Since then, scientists have begun linking Americans’ protein-rich diets to the Bay’s unhealthy state more explicitly.

Plants, animals and people couldn’t live without nitrogen. But eating meat is an incredibly inefficient way to acquire that essential nutrient. More than 90 percent of the nitrogen originally applied to a field of grain to produce animal feed, for example, never becomes part of the burger or steak a human consumes and is lost to the environment.  Much of that excess nitrogen winds up in the water, where it helps fuel the growth of algae blooms and the development every summer of fish-stressing “dead zones” in the Bay.

If everyone in the Bay watershed ate only the amount of protein recommended by the federal government’s dietary guidelines, the “reductions in nitrogen emissions would be substantial,” said James Galloway, a professor of environmental sciences at UVA. In the United States, the typical person consumes roughly 30 percent more protein than he or she needs.

Last year’s update of the dietary guidelines was the first to call out teenage boys and men, in particular, for eating too much beef, pork, chicken and eggs. Earlier drafts had urged all Americans — men and women alike — to adopt more environmentally sustainable eating practices by cutting back on meat; the final version dropped that recommendation. 

But, McGee said, linking what we eat to the environment where we live makes even more sense in the Chesapeake Bay, where food production’s implications for water quality are well known.

“Agriculture is a big part of the pollution loads to the Bay, and we can do a lot working with farmers. But, at the end of the day, farmers are responding to demand,” McGee said.

To add food choices to the nitrogen calculator, McGee said their team initially considered how much of that food is produced in the Bay watershed and how much is imported. Demand for beef, for example, far exceeds what’s produced here, while areas of the Bay such as the Delmarva Peninsula produce far more chickens than could be consumed by its residents.

While locally produced beef technically has a greater impact on water quality, the team decided not to incorporate that into the calculator, in the belief it conveys the wrong message to people.

“If everything consumed comes from outside the watershed, that wouldn’t be a good thing, either,” said McGee, whose organization recommends consuming grass-fed, locally produced beef over imported options, for example. “We bear the brunt of food that’s produced here and food that’s shipped here.”

In the end, the calculator did away with adjustments for where the food is produced in favor of getting its users to think critically about how much they’re consuming overall. It asks users how many portions of beef, chicken, pork, seafood, milk or cheese, eggs and vegetables they consume in a given week, offering suggested averages that can be tweaked.

The type of sewage system, home, land use and transportation habits of the participant are then considered before the calculator issues a letter grade — and recommendations for how to improve.

“Our individual actions may seem small, but the reality is, collectively, they make a difference,” McGee said.