Should People Eat Lower on the Food Chain?
Critical Thinking Issue
Should People Eat Lower on the Food Chain?
Energy Pyramid Representation
The energy content of a food chain is often depicted using an energy pyramid.
Each level of the food chain is represented by a rectangle, whose area correlates with the energy content available at that trophic level.
For simplicity, the energy pyramid assumes that each link in the food chain has only one source of food.
Energy and Food Consumption Examples
Example of a 75 kg (165 lb) Individual Eating Frogs:
A person weighing 75 kg would need to consume approximately 10 frogs per day to meet their energy needs, totaling about 3,000 frogs per year (approximately 300 kg or 660 lb).
Grasshopper Consumption:
Each frog consumes about 10 grasshoppers per day. Therefore, 3,000 frogs would require:
9 million grasshoppers per year; this equates to approximately 9,000 kg (19,800 lb) of grasshoppers to sustain the frogs.
Wheat for Grasshoppers:
To support this amount of grasshoppers, a corresponding amount of wheat is necessary:
A horde of this size would require 333,000 kg (732,600 lb) of wheat to sustain them for a year.
Implications of Eating Lower on the Food Chain
Energy Decrease at Higher Trophic Levels:
The energy content diminishes at each progressive level of the food chain within the pyramid.
The energy at the pyramid's apex is fundamentally linked to the number of layers present.
Comparative Analysis:
If instead of frogs, humans consumed grasshoppers:
Each person could potentially sustain themselves on 100 grasshoppers a day.
Thus, the 9 million grasshoppers would be sufficient to support 300 people for a year instead of just one.
In cases where wheat is consumed instead of grasshoppers:
333,000 kg of wheat could sustain approximately 666 people for a year.
Arguments for Herbivory
As a result of these considerations, there are suggestions that humans should adopt a vegetarian (herbivore) diet and consume directly from autotrophs, which represent the lowest level in food chains.
Plant Consumption Limitations:
Humans can eat only specific parts of certain plants. There are herbivores that can digest parts that humans can’t consume.
When consuming herbivores, more of the energy stored in plants becomes available for human consumption.
Aquatic Food Chains
Critical Challenge:
In aquatic food chains, humans predominantly rely on fish, which eat algae (the primary producers).
Due to the inability to digest most algal types, complete herbivory would significantly limit human dietary options, excluding many food chains entirely.
Environmental Considerations
Land Use and Crop Production:
In some areas of Earth, traditional crop production may harm the land, whereas grazing by herbivores does not have the same detrimental effect.
Biodiversity and Soil Conservation:
These environmental issues imply a necessary balance in food consumption practices, weighing the potential benefits of eating lower on the food chain against biodiversity and soil health.
Critical Thinking Questions
Energy Content Reduction:
Why does the energy content decrease at each higher level of a food chain? What happens to the energy lost at each level?
Mass as a Measure of Energy:
The pyramid uses mass as an approximate representation of energy value; why is mass an appropriate indicator of energy content?
List of Environmental Arguments:
Compose a list of arguments for and against adopting an entirely vegetarian diet. Consider the consequences for U.S. agriculture if there were a nationwide shift to eating lower on the food chain.
Personal Food Chain Position:
Reflect on how low you eat on the food chain and whether you would be willing to adopt a lower dietary position; provide reasoning for your decision.
Figures
The accompanying figures illustrate the energy pyramid and its relations, including:
(a) Energy pyramid representation.
(b) Grasshopper representation.
(c) Frogs that consume grasshoppers, showing the relationship between trophic levels and their energy requirements.