To take a bite out of the Chesapeake’s pollution, consumers need to watch what they put in their mouth.
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.
The scientists aren’t suggesting that people become vegetarians; only that they control protein consumption which – in the United States – averages about 40 percent more than dietary recommendations. “Instead of a 5-ounce steak, you eat a 3 ounce steak,” Galloway said. “It is that kind of reduction.”
The notion that excess nitrogen in the diet could be a problem would have seemed like a fantasy just a century ago. For most of human existence, the amount of nitrogen available for growing crops was limited, and by the early 1900s, there was growing concern that lack of nitrogen could starve the planet.
Then, German scientists figured out how to tap into the limitless supply of inert nitrogen gas that dominates the atmosphere and turn it into “reactive nitrogen” – forms that could be readily absorbed by crops. Meanwhile, farmers began more intense cropping of certain species of crops, primarily legumes such as alfalfa and soybeans, which have the ability to pull the nitrogen they need from the atmosphere.
That contributed to a 10 – to 12-fold increase in the amount of reactive nitrogen released into the U.S. environment, with new synthesized fertilizers from atmospheric nitrogen making up the largest single source. The greatest increase began in the 1960s, with the introduction of new, high-yield varieties of corn that demanded vastly increased amounts of nitrogen fertilizers to thrive.
That’s also about the same time that water quality in the Bay, and some other coastal areas, began a noticeable decline.
Consumption rates rising
Over the last several decades, Americans have been eating more in general, which means more food is produced, more nitrogen applied to the land – and more runs into the water or volatilizes into the air. According to the USDA, per capita food consumption increased 16 percent between 1970 and 2005, from 1,675 pounds annually to 1,950 pounds, which partly explains a doubling of the obesity rate during the same period.
The endless supply of fertilizer and new varieties of corn have also allowed for profound changes in what people eat. In the United States, more than half of all grain is fed to animals. For corn, perhaps the most nitrogen intensive grain, the percentage is even higher.
More grain allowed for the increased production of animals, and animal products such as milk and eggs. Per capita meat consumption in the United States has increased by nearly a third from the mid-1960s to mid-2000s according to USDA figures. But that came with an environmental price. Protein consumption, especially animal protein, is associated with high nitrogen losses.
Here’s why: Nitrogen is an essential building block for protein. Protein, on average, is 16 percent nitrogen, and the production of protein from any source – even fruits and vegetables – results in losses to the environment.
But consuming large amounts of protein-dense animal products is inherently inefficient because it typically means fertilizing crops for feed, which then must be fed to animals, which produce wastes that are difficult to reuse efficiently. When used as fertilizer, animal manure has two to three times the nitrogen and phosphorus losses as commercial fertilizers, according to a USDA Bay report released last year.
The least efficient way to get protein to a human mouth is through beef, in part because the animals live so long and therefore eat a lot and produce a lot of manure. Of 100 grams of nitrogen originally applied to the land to produce a crop, only 11 grams ends up a steak or hamburger. Some is recycled onto fields as manure, but a staggering 89 grams of nitrogen is lost to the environment along the way.
Put another way, according to figures developed for the N-PRINT calculator, 8.5 grams of nitrogen are lost for every gram that reaches a human if it comes from beef. Other forms of animal protein are somewhat better: Milk loses 5.7 grams for each gram of nitrogen that makes it to a human; pork loses 4.7 grams and poultry 3.4 grams
Shift from cereals to meat
In comparison, nitrogen coming straight from cereal grains loses only 1.4 grams for every gram consumed.
The shift from cereal-dominated diets that were common a century ago, to today’s more protein-intensive diets, has profound implications for water quality, as the decline in the Bay tracks with increased fertilizer usage dating to the 1960s. What has happened to the Bay may be a preview of what lies in store for many other coastal water bodies: As nations become more affluent, scientists say, the trend is for their populations to eat higher on the food chain.
That link was driven home in a 2010 paper by scientists from the University of Pittsburgh who analyzed the relationship between food consumption patterns and coastal eutrophication. Growing populations and increased consumer preference for high-protein goods are likely to worsen water quality in coastal areas around the world, they reported. But, they said, “changing food purchase behaviors may be an effective mitigation strategy.”
The situation in the Bay and other parts of the country would be worse except that the food production system in the United States has become more efficient over the years. A recent report from the EPA’s Science Advisory Board showed that a kilogram of nitrogen that grew 43 kilograms of grain on average in 1975 produced 65 kilograms of grain by 2005. Likewise, feeding efficiencies in animal agriculture have resulted in more protein being produced with fewer nitrogen inputs.
Still, as the Bay region’s population increases, efforts to maintain the Bay TMDL pollution diet – which sets absolute limits on the amount of nitrogen and phosphorus that can enter the Chesapeake – will be challenged if people can’t be persuaded to change what they eat.
Controlling runoff has been a daunting challenge as state and federal agencies have spent hundreds of millions of dollars to help farmers install streamside buffers or plant cover crops. Those tactics, though, try to soak up nitrogen after it has been released into the environment. Changes in diet mean less fertilizer is needed: in effect, stopping pollution before it starts.
“It’s not either or, but you can’t just be focused on the back end,” Galloway said. “Our view is that you have to pay a lot more attention to controlling nutrients at the front end, as opposed to the back end.”
Others have made similar suggestions.
The National Research Council, a part of the National Academies of Science, said in a review of Bay Program nutrient reduction goals last year that the region needed to consider a wide range of possible strategies, “including some that are receiving little, if any, consideration today.” Among them: “changing diets.”
The EPA’s Science Advisory Board last year called for a more active agency policy to reduce nitrogen releases into the environment. One of its recommendations was for the agency to work with the USDA to stress how both human and environmental health could be improved through better diets. Without such a change the report said, nitrogen inputs – and losses – from agriculture would likely increase.
The missing diet message
It’s a message most people never get. Among actions people can take to help the Chesapeake, eating a Bay-friendly, and healthier, diet is not on the menu of options provided by government agencies or environmental groups in their educational materials.
The state-federal Chesapeake Bay Program’s tips on ways to help the Bay advises people to drive wisely to reduce vehicle emissions, apply less fertilizer on their lawns, install rain barrels and similar actions which, while noble, have small impacts on one’s nitrogen footprint compared to diet changes.
For instance, the difference between switching from an SUV to a sedan would reduce a person’s nitrogen footprint by 7 pounds a year by producing less nitrogen in vehicle exhaust. Reducing protein to recommended levels and cutting waste would slash it by more than 30 pounds, according to N-PRINT data.
Selling the sedan and eschewing public transportation for a bike or walking saves only 13 pounds annually. Put another way: Someone driving a Smart Car but trying to slim down on a high-protein diet may have a much bigger nitrogen impact than someone cruising around in Humvee who eats recommended amounts of protein.
Nonetheless, the subject of diet is something of a sacred cow. “It’s a sensitive issue,” said Allison Leach, a University of Virginia research assistant who led the development of the N-PRINT calculator. “People don’t like to be told what to eat. That is the general reaction we’ve gotten.”
Diet issue not discussed
Rich Batiuk, associate director for science with the EPA’s Bay Program Office, said the notion of human diet as a nutrient control strategy hasn’t come up in meetings among Bay Program participants.
“That really hasn’t gotten out there,” he said. “It’s an interesting concept. It just reminds all of us that every little action we take – what we consume, how we drive, when we turn the lights on – it’s all interconnected.”
The Chesapeake Bay Foundation has its own nutrient footprint calculator, but it doesn’t include the impact of food consumption. Beth McGee, senior scientist with the Chesapeake Bay Foundation, said the group has talked with the UVA researchers about updating the calculator to include at least some aspects of food consumption.
But, she added, diet can be a difficult issue to push. “We have to not come across as being preachy, and not make people feel bad for eating meat, but just say they should be a little more thoughtful about what they eat.”
Some worry that such a change could hurt farmers, which diet change advocates acknowledge is likely true for some individuals. But a 2005 USDA report suggested that following its recommended diet guidelines could boost overall profitability, in part because people would be eating more high-value foods such as fruit, vegetables and whole grains. Also, any substantial diet shift, most agree, would take place over many years – if not generations.
But the issue is also complex, which can complicate messaging. Food production can be highly mobile, so the exact benefit in reducing consumption in the Bay watershed is blurred as food is imported and exported across watershed boundaries. (The same is true for electric generation: whether an individual’s conservation effort helps the Bay depends on where, and how, their electricity is produced.)
Because almost all coastal systems are overloaded with nitrogen, someone will almost certainly be helped, Leach said. “Generally speaking, if you are making more informed food choices that are reducing nitrogen losses, an environment – even if it is not yours – is experiencing a benefit from your choices.”
Some benefits are certain to accrue entirely within the watershed, though. Adults typically don’t accumulate protein in their bodies, so whatever they eat, they also excrete. Reducing protein means less nitrogen content in human waste.
For people whose sewage goes to a treatment plant using advanced nutrient removal technology, that wouldn’t make a difference. But for those with septic systems, or hooked to sewage treatment plants without nutrient removal technology, a diet change could directly reduce their nitrogen contribution to local streams and the Bay. “Much of the nitrogen that is being released as human waste is all going to end up in your watershed unless it is treated,” Leach said.
The average person generates a bit more than 11 pounds of nitrogen annually in their waste, according to N-PRINT.
Another problem is that the reduced protein message can run counter to other messages people get about food production. For instance, the push for producing meat on grazing systems instead of animal feedlots doesn’t necessarily mean less nitrogen pollution. Animals that graze tend to live longer, and therefore produce more waste, making the production less efficient. Whether the pasture contains legumes, such as alfalfa, or relies on fertilizer for its nitrogen source also makes a big difference on how efficient the system is.
And buying local goods doesn’t necessarily reduce the nitrogen footprint, either. “There may be lots of good reasons to eat local food or grazed beef,” Leach said, “it’s just that nitrogen isn’t one of them.”
Put animals on a diet
Because of such complexities in the food production system – and the difficulty of persuading people to eat a healthier diet – some like Kohn think it is more likely that improvements will be made by optimizing animal diets, rather than human diets. “I think we’ll be more successful in controlling what animals eat than we will in controlling what humans eat,” he said.
Many dairy farmers in the Bay watershed already produce milk with less nitrogen inputs than those in other states, Kohn noted. Unlike people, those animals don’t have much choice about what they consume.
People do, he noted – but they make choices for other reasons, such as taste and convenience. “You don’t necessarily eat what’s good for you, let alone what’s good for the environment,” Kohn observed.
But there are hints that trends could change. At the University of Virginia, the N-PRINT calculator is being used to develop a strategy that reduces the university’s nitrogen footprint – which may include substitutions for high-protein foods.
In Germany and France, meat consumption has declined 15 percent and 10 percent respectively over the last decade. Overall, in Europe, meat consumption has been leveling off or declining.
Even in the United States, per capita meat consumption has declined the last few years, although analysts are unsure whether that’s driven by a lasting change in eating habits or by poor economic conditions.
And with the Bay cleanup expected to cost $30 billion to $40 billion a year using its traditional menu of nutrient reduction tactics, promoting diet change is one way that could not just reduce costs – but save money.
A paper about human health impacts related to nitrogen that was published in Frontiers in Ecology in 2003, noted that getting consumers to adopt a low-meat Mediterranean diet was a “particularly intriguing” notion because it would not only reduce nitrogen pollution, but has also been linked to reduced incidences of heart disease, cancer and several other ailments.
“Thus, the potential clearly exists for maximizing the health benefits of some human alteration of the [nitrogen] cycle, while also greatly reducing both the environmental and health costs,” the paper concluded.
But first, diet has to be on the plate of cleanup actions
There’s plenty of nitrogen around us, but only ‘reactive nitrogen’ can be used by plants
The bulk of the Earth’s atmosphere is N2, nitrogen gas, a form that most organisms can’t use in their metabolism.
Over the last century, though, humans have found ways to greatly increase the amount of biologically available nitrogen. These forms, part of what is collectively known as “reactive nitrogen,” stem from creating nitrogen fertilizer from N2 in the atmosphere through chemical processes (the largest single source of reactive nitrogen); enhanced production of nitrogen-fixing legume plants in agriculture; and the combustion of fossil fuels, which produce reactive nitrogen emissions in the form of nitrogen oxides.
By some estimates, these processes have increased the amount of nitrogen available in the U.S. environment 10 to 12 times over the last century. Globally, the amount of nitrogen available in the environment has doubled during that time. (In comparison, humans have increased the amount of carbon in the atmosphere by about 10 percent during the same period).
While increased nitrogen availability has produced fertilizers that have helped to feed the world, it has also created problems. Nitrogen in air pollution creates smog, particulate matter and acid rain, which harm human health, reduce crop and forest growth, impair ecosystems and damage streams and lakes.
Excess nitrogen, whether from air or fertilizers, also has major impacts on land and water, leading to biodiversity declines in grasslands, the spread of exotic species and the eutrophication of coastal waters and other problems. Some forms of reactive nitrogen also contribute to global warming.
The National Academy of Sciences has called managing human changes to the nitrogen cycle one of the “grand challenges” facing science in the 21st Century.
What’s Your Footprint?
People who want to learn how their actions affect their nitrogen “footprint” can easily do so by tapping into an online nitrogen calculator developed by a team of scientists from around the world.
The calculator, which debuted last year, is intended to help raise awareness of the problems associated with excess nitrogen in the environment, and it offers people tips to minimize their impact.
By answering a series of questions, the calculator shows how changes in energy use, driving – and particularly diet – can influence an individual’s footprint.
The calculator is part of the N-PRINT project ,which will eventually include a number of tools to help individuals and policy makers make decisions to reduce their environmental impact.
The N-PRINT calculator is found at: http://www.n-print.org/
The Chesapeake Bay Foundation also has an online nitrogen calculator to help people gauge their nitrogen footprint. For now, it lacks a diet component, but the group hopes to incorporate that in the future.
The CBF calculator is found at: www.cbf.org/yourbayfootprint.