There is a favorite saying of mine, “There are no twenty-dollar bills lying around on the street because someone’s picked them up already.” In other words, opportunities are hard to come by, because millions are trying at the same time, many more desperate, and what little low-hanging fruit there is has already been plucked.
So with this knowledge in mind, I was thoroughly astounded when I learned about the energy pyramid in ecosystems in my biology class. It states that on each successive level of the food chain, the total energy available in biomass decreases by a factor of approximately 10. In other words, the efficiency of energy transfer by predation is between 5-20%. And therefore, 80-95% of energy at a given level is unavailable at the next.
The reason for this is fairly obvious. Plants, producers at the lowest level of the pyramid, perform the process of photosynthesis to convert sunlight into glucose. This glucose then has two purposes – synthesis into carbohydrate polymers that “build” the plant (contribute to its edibleness) and fuel for cellular respiration, which provides energy for the everyday processes that a plant goes through. At the next level, primary consumers, herbivores, consume the edible parts of the plant, carbohydrate polymers such as starch and glucose, and then use that for the same two purposes – building biomass, or tissues such as muscle and bone, and energy for “maintenance.” So in each case, at each level, we see that an organism takes in energy, which it uses for (a) building biomass for other things to eat for energy, and (b) using energy to fuel processes to keep itself alive. As it happens, (b) is a need that is allocated 9 times more energy than (a).
But all of that is very intuitive. So the major question is…why should humans eat meat? And the simple answer is, that other than for the fact that it tastes really good, there is no good reason. In fact, there are a whole slew of reasons not to do so.
This argument doesn’t delve into ethical considerations, although I do digress to say that my math teacher did say that the reason he stopped eating meat at a young age was because he couldn’t bare to take away the “feeling of life” from any living creature. A puppy might not ponder the reasons and nuances of its existence (and humans don’t do this most of the time, either) but if you hold its head underwater, the puppy feels a very strong sense of “aliveness” coupled with a very strong sense that its “aliveness” is being threatened. So how could you take that away from something?
Of course, people say that it’s only “natural” for people to eat meat, but what’s “natural” about what we do anyway? Multiple levels of the food chain haven’t always been there – presumably there were once only producers and primary consumers (consumers of the lowest level, or vegetarians). At such a point, the “low-hanging fruit” was no longer the literal low-hanging fruit competed for with other herbivores but rather the defenseless herbivores themselves – another level of consumers could emerge, at 10% of the size of the lower energy level. And thus the energy pyramid would develop an equilibrium with each level no bigger than 10% of the level immediately lower and no smaller than 10 times that of the level above (there would be other restrictions as well, depending on resources such as water, space…)
Enter human civilization. As omnivores, humans are generally primary, secondary, or tertiary consumers. The problem is that humans possess far more total biomass than any other species of large mammals, and that our use of complex tools allows us to at least temporarily evade the limits imposed by the energy pyramid, especially predators to check population growth. The other problem is that humans, despite being perfectly able to subsist as primary producers, domesticate large amounts of primary consumers, which is extremely inefficient. It’s basically like going from “If life gives you lemons, make lemonade” to “If life gives you lemons, use those lemons to continually feed some large mammal for years before slaughtering and eating it.” It’s not very difficult to see which is more efficient.
Just for reference, here’s a graph that I found on the NY Times’ Green Blog. It plots the amount of CO2 emissions to produce different types of food:
Lamb’s not such a popular product, but the changes that even a meat-eater can make by switching from livestock to poultry are astounding!
Since I’m doing this from an environmentalist perspective, there’s no reason to be an absolutist. But if as a human race, we’re having trouble feeding each other and squandering our precious resources to add another extraneous level to the food pyramid, and we should really look into vegetarianism. The Amazon rainforest, a carbon sink, is slash-and-burn deforested (releasing CO2) at a startling rate to accommodate cows, which graze short-term on poor-quality soil while emitting methane, another greenhouse gas, resulting in a triple whammy for emission control efforts.
Dennis Avery, Director of the Centre for Global Food Issues, said that “The world must create five billion vegans in the next several decades, or triple its total farm output without using more land.” The clock’s ticking. So yours truly has decided to make a small sacrifice with huge power-of-ten payoffs. Because even if there seem to be no 20-dollar bills lying around on the ground, going vegetarian seems to be a climate change-curbing low-hanging fruit that’s just dying to be plucked.