Food chains, food choices and the environment

Katherine Kornobis
10 November 2014

Above: Image © istockphoto.com/IDijkinga

What is your favourite food? Your answer may say a lot about your position in your food chain and the environmental impact of your food choices. For example, if you are a big fan of hamburgers, you may be at the top of your food chain but you also eat food that takes a lot of energy to produce.

Did You Know? Eating protein can help you lose weight by making you feel fuller for longer, which prevents unhealthy snacking. A few unexpected protein sources include soy (what tofu is made of!), Greek yogurt and beans.

In the 21st century, many people can eat whatever they want, whenever they want. All sorts of fruits, vegetables, meats, grains and dairy products are available at the supermarket year-round. Many people concerned about the environment will consider the energy used to ship some foods halfway around the world. However, you may also want to consider how a particular food’s place in its own food chain or food web affects how much energy went into producing it.

Trophic levels

An organism’s position in its food chain is called its trophic level. Organisms with a trophic level of one (right at the bottom) are called primary producers. They harvest their energy from the sun through a process called photosynthesis. Primary producers include all sorts of plants.

Organisms that eat primary producers have a trophic level of two and are called primary consumers. Depending on the ecosystem, a food chain may have many different trophic levels, such as secondary and tertiary consumers.The more plant material a species consumes, the lower its trophic level.

So where do humans fall on the trophic scale? Many people think we are right at the top. In fact, scientists have assigned us a trophic level similar to that of pigs and anchovies. After all, we like to eat strawberries and lettuce, not just fish and chicken.

In fact, a person’s trophic level may change depending on where they live. For example, most people in Burundi eat almost exclusively plant material, and therefore have a lower trophic position. By contrast, people in Iceland eat more meat than plants due to the climate, and have a much higher trophic position.

Lost energy

Did You Know? Pound for pound, farmed salmon may be the most eco-friendly meat: it takes about a pound of fish feed to produce a pound of salmon meat. With improvements in aquaculture, salmon could become an even more sustainable food source.

With each step higher on the trophic scale, about 90% of the energy from the previous level is lost. So organisms that eat at a lower trophic level, such as primary producers and primary consumers, get more out of their food. And the food consumed by a meat-eating Icelander will require a lot more energy to produce than the food consumed by a plant-eating Burundian.

Imagine that a patch of grass absorbs 1000 energy units from the sun. The cow that eats the grass will only absorb 100 energy units. And by the time you eat your delicious barbecued hamburger, you only get 10 of energy units from the beef for every 1000 that were originally absorbed by the grass. In fact, to produce one pound of beef, you need about seven pounds of plant material for the cow to eat.

Efficient eating

If you are concerned about the environmental impact of your food choices, one thing you can do is eat more foods with a lower trophic level. Since less energy is lost to intermediate trophic levels, these foods will allow you to directly consume more of the energy used to produce them. From this perspective, a vegetarian diet is much more eco-friendly. As an added bonus, vegetarian foods also tend to cost less!

However, if you are not ready to plunge head-first into vegetarianism, you can try out “Meatless Mondays”. Every Monday, many families swap out their roasted chicken or pork chops for curried chick peas or vegetarian chili with texturized vegetable protein (TVP) instead of ground beef.

Are you overwhelmed by the number of choices available at the supermarket or the food court? What do you think your trophic level is? Do you think eating less meat and more plant products is a good way of protecting the environment? Let me know by leaving a comment!

Learn more!

Video discussing what happens to energy that is not passed on to the next trophic level in a food chain, using Asian deer and tigers as an example.

What happens to energy in food chains? (2014)
BBC Learning Zone

Article discussing research into and factors affecting humans’ place on the food chain.

Where Do Humans Really Rank on the Food Chain? (2013)
Joseph Stomberg, Smithsonian.com

Katherine Kornobis

Katherine is from Waterloo, Ontario, and is a biology & chemistry teacher in the Waterloo Region District School Board. Her passions include travel, the environment, teaching and learning new things.

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Avatar  izzaty ilmi

should people eat lower on the food chain??
why???
can you suggest the way to eat lower on the food chain?