Online Tool Shows How What You Eat Affects Pollution

Looking to lead a more eco-friendly lifestyle? You could start by cutting back on meat. A new nitrogen footprint calculator shows you the impact your diet has on the environment.
You may have heard of the concept of a carbon footprint. That's how much of the greenhouse gas carbon dioxide your lifestyle generates. Now researchers have developed a way to measure how our lifestyle - and in particular our diets - impacts another major source of climate-changing pollution: nitrogen.
Everything needs nitrogen, from plants to plankton¹ to people. It's a key element in the proteins that make up our bodies.
Good news, bad news
In the early twentieth century, scientists figured out a way to take nitrogen out of the air and turn it into a form that plants could use. The invention of synthetic² nitrogen fertilizer dramatically improved food production.
"That's the good news," says environmental sciences professor Jim Galloway at the University of Virginia. "We're able to feed the world's population because of this wonderful invention."
The bad news, Galloway says, is that many parts of the world use far too much nitrogen fertilizer. Burning fossil fuels also creates nitrogen pollution. Galloway says the excess nitrogen "contributes to smog, acid rain, loss of biodiversity, dead zones along the coast, global warming, stratospheric ozone³ depletion⁴. The list is quite long."
Visualizing⁵ impacts
Galloway and his colleagues developed the nitrogen footprint calculator to show how people's behaviors contribute to that long list of environmental impacts.
The calculator starts with a graph showing the amount of nitrogen pollution produced by the average person. One of the first things you notice is that food is far and away the biggest contributor: 72 percent of the 42 kilograms the average American produces comes from food consumption. Housing, transportation and goods and services make up the rest.
To see exactly how your diet affects your nitrogen footprint, the calculator lets you adjust how many times a week you eat 16 different kinds of foods.
"As you change your consumption, you can see how the graph changes," says co-creator Allison Leach⁶ at the University of Virginia. "So as you scale down one bar, you can see your nitrogen footprint shrinking."
Too much protein
Americans eat far more protein on average than the U.S. Department of Agriculture recommends, Leach says. "Reducing your protein to the recommended levels is going to have a huge impact on reducing your nitrogen footprint. [That] reduces it by almost half."
Reducing the amount of animal protein is one of the quickest ways to shrink that footprint. Galloway says that's because feeding plants to animals is an inefficient⁷ use of nitrogen.
"For large animals like beef, a very large fraction of the nitrogen that enters the cow's mouth is excreted out the back end," he says.
Beef is less efficient than chicken or pork, while plant sources like legumes are the most efficient, Leach says.
Nitrogen footprints around the world
She and her colleagues also created nitrogen footprint calculators for Germany and the Netherlands. She says their footprints are smaller largely because they tend to eat less meat, not because of major differences in their farming practices.
"Industrialized agriculture production is pretty consistent among developed countries. But it's going to be very different in developing countries."
The next step, Leach says, is a nitrogen footprint calculator for India, a developing country where farming practices are very different from in the industrialized world.
Footprints growing
But even in the developing world, nitrogen footprints are changing. The world's population is not only growing, it's also growing richer. One consequence is that people are eating more animal protein. Galloway says they have looked at what the world might look like in 2050 - and it raises concerns.
"If the entire world had the per capita resource-use habits that people in North America have, then we would be putting three to four to five times more reactive nitrogen into the environment than we are now," he says. "And that's frankly⁸ untenable. Our ecosystems⁹ can't handle that."
Galloway says that's why it's so important that we all do a better job managing the amount of nitrogen we put on our fields, in our mouths, and into our environment.

1 plankton   

n.浮游生物

参考例句：

• Plankton is at the bottom of the marine food chain.浮游生物处于海洋食物链的最底层。
• The plankton in the sea feeds many kinds of animals. 海的浮游生物成为很多种动物的食物。

2 synthetic   

adj.合成的，人工的；综合的；n.人工制品

参考例句：

• We felt the salesman's synthetic friendliness.我们感觉到那位销售员的虚情假意。
• It's a synthetic diamond.这是人造钻石。

3 ozone   

n.臭氧，新鲜空气

参考例句：

• The ozone layer is a protective layer around the planet Earth.臭氧层是地球的保护层。
• The capacity of ozone can adjust according of requirement.臭氧的产量可根据需要或调节。

4 depletion   

n.耗尽，枯竭

参考例句：

• Increased consumption of water has led to rapid depletion of groundwater reserves.用水量的增加导致了地下水贮备迅速枯竭。
• Farmers should rotate crops every season to prevent depletion of the soil.农夫每季应该要轮耕，以免耗尽土壤。

5 visualizing   

肉眼观察

参考例句：

• Nevertheless, the Bohr model is still useful for visualizing the structure of an atom. 然而，玻尔模型仍有利于使原子结构形象化。
• Try to strengthen this energy field by visualizing the ball growing stronger. 通过想象能量球变得更强壮设法加强这能量场。

6 leach   

v.分离，过滤掉；n.过滤；过滤器

参考例句：

• Liquid water can leach soluble materials from the interface.液态水能够从界面溶解出可溶性物质。
• They believe that the humic materials are leached from decaying plant materials.他们认为腐植物料是从腐烂的植物体浸沥而来。

7 inefficient   

adj.效率低的，无效的

参考例句：

• The inefficient operation cost the firm a lot of money.低效率的运作使该公司损失了许多钱。
• Their communication systems are inefficient in the extreme.他们的通讯系统效率非常差。

8 frankly   

adv.坦白地，直率地；坦率地说

参考例句：

• To speak frankly, I don't like the idea at all.老实说，我一点也不赞成这个主意。
• Frankly speaking, I'm not opposed to reform.坦率地说，我不反对改革。

9 ecosystems   

n.生态系统( ecosystem的名词复数 )

参考例句：

• There are highly sensitive and delicately balanced ecosystems in the forest. 森林里有高度敏感、灵敏平衡的各种生态系统。 来自《简明英汉词典》
• Madagascar's ecosystems range from rainforest to semi-desert. 马达加斯加生态系统类型多样，从雨林到半荒漠等不一而足。 来自辞典例句