Walter Simpson - The Meatless Diet
Meat-eating Environmentalist? - Lisa Rogers
Ultimately everything we do is driven by energy received from the sun. Not only does the sun keep us warm but it also powers the production of food via photosynthesis. Carbon dioxide combines with water in the presence of sunlight and chlorophyll (recall that chlorophyll is found ONLY in plants that can photosynthesize, i.e. green plants) to produce the sugar glucose and oxygen. Plants can then use the glucose to build all other compounds necessary for growth and we can use the oxygen to breathe. In essence, we have taken the energy from sunlight and stored it in a plant. When we need energy, we eat the plant and energy is released.
A green plant produces stores of energy and is called a producer; everything else is a consumer because it consumes the producers OR other consumers. We can arrange the producers and consumers such that the producers occupy the bottom of a pyramid called the first trophic level. The remaining consumers occupy higher levels (second, third, etc.) depending on what they eat. Categorizing organisms by placing them on different levels of a pyramid greatly oversimplifies the picture in that it implies some kind of linearity (i.e. a food chain). Although this linearity helps us conceptualize what's going on, in reality, the distribution of energy among organisms is rather complex where different food chains are generally interconnected to form food webs.
Let's return to the idea of a food chain though because it helps illustrate an idea. As an example, let's imagine a possible five level food chain with grass at the bottom followed by grasshoppers, frogs, fish and humans. As a grasshopper, I'm sitting happily chomping away on some fine tasty grass. The energy I get from the grass I use to grow bigger, make babies, and whatever else grasshoppers do. However, I don't use ALL of the energy; some of it is wasted as heat. I do though become a delicious morsel for the local frog community. As a frog then, I spy several grasshoppers and make a meal of them. Again, I use the energy to do whatever it is frogs do: grow bigger, hop, swim, croak, etc. All of those activities take energy but I don't use ALL of the energy, again some is wasted as heat. A similar process occurs for the organisms on the remaining trophic levels too. Each time I move up a trophic level, I lose energy so that by the time I get to the top level, I have wasted an enormous amount of energy. As a general rule of thumb, as I move up a food chain, I lose about 90% of the energy that was stored at each level. In other words, the process is not very efficient. Therefore, the amount of energy I have available at any particular trophic level (which is much more than is useful) determines how many organisms I can sustain at the next higher level.
We can use the same food chain to illustrate this but let's use something that is a little more easily understood than energy and that's money. If we start with $100 on the first level and it costs us 90% of what's in our pocket in order to move up one level of the chain, then on the second level we'll have $10. We can continue the payment schedule so that by the time we get to the top we have only ONE CENT left in our pocket! In other words, it cost us 99.99% of what we had to get to the top. If we apply this to the energy of food chains, we see that it would "cost" us much less to eat at lower trophic levels. Some people have become vegetarians for exactly this reason; i.e. it is more environmentally friendly to be a vegetarian than it is to be a meat-eater.
For the last examples, we started at the bottom of the food chain. We can also look at this system starting from the top. We could ask the question, as a human with one cent in my pocket, how much money does it take at lower levels to support me? If we look one level down (in this case to the fourth level) we'd say it takes ten times what I have to support me. But if we continue looking down the chain, we see that it takes ten times that much at the third level, and another ten times at the second and finally another ten times at the first level. This means that overall in order to support me it takes $100 for every cent I have or about 10,000 times what I have! In the environment this translates to biomass and the space required for support of that biomass. In other words it takes a lot of space to support one human being. Now multiply that by the six billion people we have on the planet. Thatıs a lot of energy and space. The question becomes, is there enough?
- How much meat do you consume in a year's time? How does this compare to the meat consumption in other countries?
- Is the meat you consume produced in an environmentally friendly manner?
- Do you consume at low, high or varied trophic levels? Does it matter to you? Why?
- How could you personally be more environmentally friendly in regards to food webs?
- What Is A Foodchain?http://www.usca.sc.edu/AEdc442/442991/foodchain.html
This site provides a nice description of foodchains and foodwebs and is not overly technical.
- The Foodchain As An Example of a Systemhttp://www.geog.ouc.bc.ca/physgeog/contents/4e.html
This site uses a foodchain as an example of a system and includes a lot of detailed cross-references.
- Eating Green - The Meatless Diethttp://www.renewableenergyworks.com/sustainability/meatless.html
Walter Simpson discusses the consequences of eating high on the foodchain and explains why eating meat is energy and resource inefficient.
- Meat-eating Environmentalist? How Can That Be? - Lisa Rogershttp://www.veg.ca/lifelines/marapr/meat.htm
Lisa Rogers outlines why vegetarianism is the obvious choice for environmentalists in this essay from 1998.
- Ecology of the Sibun River, Belizehttp://www.belizeanjourneys.com/sibun/ecology.html
This site gives many examples of the interactions of foodchains; very descriptive, very educational.
- Earthtrends @ World Resources Institutehttp://earthtrends.wri.org/
This site is filled with a plethora of information. You can use the Agriculture and Food data tables to compare global grain, tuber and meat production and consumption.
All material (except for some code and external links) © Jeffery A. Schneider, 2003