Humans as Omnivores

1. Humans are omnivores, meaning they naturally consume foods from multiple biological kingdoms including fungi, plants, meat, and fish.
2. Omnivory allows dietary flexibility, meaning humans can shift their consumption 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 and Sustainability

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

Comparing Crop Production and Livestock Production

1. Efficiency of Food Yield per Unit Land

1. Crops provide a higher yield per unit of land than livestock, because plant biomass can be consumed directly rather than being converted to animal biomass.
2. Producing livestock requires additional land to grow animal feed, significantly increasing the land footprint.
3. Livestock farming also requires grazing land, which takes up large global land areas that could otherwise grow food for direct human consumption.
4. Intensive livestock farming concentrates animals indoors at high densities, increasing disease risks and environmental impacts.

2. Efficiency of Resource Use (Water, Land, Energy)

1. Beef, lamb, prawns, and cheese have extremely high water and carbon footprints, as shown in global emission data.
2. Livestock require energy for movement, body heat, and metabolism, so feed-to-meat conversion efficiency is low.
3. Producing 1 kilogram of beef requires producing approximately 10 kilograms of plant feed, causing massive energy inefficiency.

Sustainability Benefits of Plant-Based Diets

1. Lower environmental impact

1. Plant-based diets reduce greenhouse gas emissions, because livestock (especially ruminants like cattle) produce methane.
2. Eating more plant-based foods reduces the 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 more crops directly for humans.
4. One global study estimated that a complete global shift to a vegan diet could reduce agricultural land use by up to 75 percent, an area roughly the size of North America plus Brazil.

2. Increased efficiency in global food distribution

1. Plant-based diets increase the total food available because less land is wasted producing animal feed.
2. A larger percentage 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 only)

1. Plant-based diets raise important ethical questions, including animal rights, fairness in resource distribution, and minimizing environmental harm.
2. Religious, cultural, and environmental value systems influence dietary choices, making sustainability a complex ethical issue.
3. Animal welfare concerns, ecocentric values, and environmental ethics all support reducing meat consumption.

Global Strategies for Sustainable Food Supply

Why Global Food Systems Must Become More Sustainable

1. Global agriculture produces enough food to feed the world, yet distribution inequalities lead to hunger in some regions and waste in others.
2. At least one-third of all food produced is wasted, making food waste one of the biggest barriers to sustainability.
3. Modern agriculture contributes heavily to climate change, via nitrous oxide from soils, methane from livestock, and emissions from fertilizer production.
4. Sustainable food systems aim to reduce environmental damage while maintaining or increasing yield without expanding farmland.

Strategies to Reduce Demand and Food Waste

1. Reducing Dietary Demand for Unsustainable Foods

1. Reducing consumption of resource-intensive foods such as beef decreases pressure on land, water, and the climate.
2. Plant-based meat substitutes provide high-protein alternatives that reduce reliance on livestock.
3. Cultural, economic, and ethical factors influence dietary choices, making policy interventions necessary.
4. Governments can shift demand using taxes on unsustainable products or subsidies for sustainable ones.
5. Reducing demand does not automatically guarantee redistribution, because food markets respond to economic incentives, not ethics.

2. Reducing Food Waste

1. Food waste occurs at every stage of the supply chain, from storage and transport to retail and households.
2. One-third of global food is wasted, representing lost resources, emissions, and money.
3. SDG 12.3 aims to reduce food waste by 50 percent by 2030.
4. Extending food shelf life reduces consumer waste, requiring improved packaging, refrigeration, and atmospheric control during transport.
5. Redistribution programs address inequality, directing unsold food to communities facing shortages.

Strategies to Reduce Greenhouse Gas Emissions from Food Production

1. Reducing Nitrous Oxide Emissions

1. Nitrous oxide emissions arise largely from denitrifying bacteria in nitrogen-enriched soils.
2. Applying excessive nitrogen fertilizers increases nitrification and denitrification, raising N₂O emissions.
3. Reducing fertilizer use and improving timing can limit N₂O release.
4. Alternatives such as organic fertilizers, cover crops, and mixed cropping reduce the need for synthetic fertilizers.