Total ecologically equivalent calories Number of calories Ecologically equivalent Diet Source of calories consumed calories 100% plant Plant 0% animal Animal 90% plant Plant 1800 1800 3800 10% animal Animal 200 2000 50% plant Plant 50% animal Animal 0% plant Plant 100% animal Animal
In ecological systems, a rough rule of thumb is that when energy
is transferred from plants to plant-eaters or from prey
to predator, the efficiency is only about 10% (p. 72). Much
of this inefficiency is a consequence of the second law of
thermodynamics. Another way to think of this is that eating 1
calorie of material from an animal is the ecological equivalent
of eating 10 calories of plant material.
Humans are considered omnivores because we can eat both
plants and animals. Our food choices have significant ecological
impacts. With this in mind, calculate the ecological
energy requirements for four different diets, each of which
provides a total of 2000 dietary calories per day.
Describe some challenges of providing food for the
growing human population, especially as people in many
poorer nations develop a taste for an American-style diet
rich in animal protein and fat.
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