IB Environmental systems and societies 5.2E Diet and Food Security Notes

Eating Lower on the Food Chain Feeds More People With Less

1. Because roughly 90 percent of energy is lost at each trophic level, plant-based diets deliver far more food per unit of land, water, and energy than meat.
2. This article links diet to trophic efficiency, resource use, greenhouse gas reduction, and food security.

Humans as Omnivores

1. Humans are omnivores, eating foods from several kingdoms including fungi, plants, meat, and fish.
2. Omnivory allows dietary flexibility, so humans can shift what they eat based on ecological, cultural, and economic factors.
3. Human diets vary widely worldwide, shaped by cultural traditions, religious rules, resource availability, affordability, and ecosystem productivity.

Trophic Levels: Why Lower Diets Are More Sustainable

1. Diets lower in trophic levels are more sustainable, because less energy is lost between food chain steps.
2. Plants are producers at the first trophic level, capturing energy from sunlight through photosynthesis.
3. Livestock occupy higher trophic levels, so producing meat requires more land, water, and feed inputs.
4. Energy transfer follows the second law of thermodynamics, so about 90 percent of energy is lost at each trophic level.
5. Eating plant-based foods bypasses the energy losses that occur when plants are first fed to animals.

Crops Beat Livestock on Land, Water, and Energy

Food Yield per Unit of Land

1. Crops give a higher yield per unit of land than livestock, because plant biomass is eaten directly rather than converted to animal biomass.
2. Livestock need extra land to grow their feed, which greatly increases the land footprint.
3. Livestock also need grazing land, taking up large areas that could otherwise grow food for people.
4. Intensive livestock farming packs animals indoors at high densities, raising disease risks and environmental impacts.

Water, Land, and Energy Use

1. Beef, lamb, prawns, and cheese have very high water and carbon footprints, as global emission data show.
2. Livestock burn energy on movement, body heat, and metabolism, so feed-to-meat conversion is inefficient.
3. Beef needs far more feed per kilogram than plant protein, commonly cited at around 25 kilograms of feed per kilogram of beef.
4. This large feed requirement makes beef one of the most energy-inefficient common foods.

Plant-Based Diets Cut Emissions and Free Up Land

Lower Environmental Impact

1. Plant-based diets reduce greenhouse gas emissions, because ruminant livestock such as cattle produce methane.
2. Eating more plant-based food lowers demand for resource-intensive livestock farming.
3. Shifting to lower-trophic-level foods frees up large areas of land, which could be rewilded, reforested, or used to grow crops for people.
4. One global study estimated that a full shift to a vegan diet could cut farmland by around 75 percent (Poore and Nemecek, 2018), an area roughly equal to the United States, China, the European Union, and Australia combined.

More Efficient Global Food Distribution

1. Plant-based diets increase the total food available, because less land is wasted producing animal feed.
2. A larger share of Earth's net primary productivity becomes available for human consumption.
3. More efficient land use reduces pressure for deforestation, protecting biodiversity and ecosystem services.

Ethical Considerations (HL)

1. Plant-based diets raise ethical questions about animal rights, fairness in resource distribution, and minimising environmental harm.
2. Religious, cultural, and environmental value systems shape dietary choices, making the ethics genuinely complex.
3. Animal welfare concerns and ecocentric values both support reducing meat consumption.