5.2G Sustainability of different diets (HL) Notes

Sustainability of Different Diets

1. The sustainability of a diet depends on how food is produced, processed, transported and consumed, making it a multi-layered environmental, social and economic issue.
2. Factors such as supply chain length, type of farming techniques, food miles, and shifts in societal eating habits strongly influence environmental impact.
3. A sustainable diet aims to meet nutritional needs while minimising negative impacts on ecosystems, climate, biodiversity, and resource availability.

Supply Chain Length & Sustainability

1. A supply chain includes every stage from production to processing, packaging, transport, retailing, and consumption.
2. Long supply chains involve multiple intermediaries, such as distributors, processors, wholesalers and retailers.
3. Each additional stage increases energy use, emissions, packaging, refrigeration needs and financial cost.

Environmental Impacts of Long Supply Chains

1. Long supply chains increase total fuel usage and CO₂ emissions, especially when refrigeration or air transport is required.
2. Physical distance increases food miles, a measure of environmental impact from transport.
3. Social and economic distance grows because less profit reaches farmers, and consumers become disconnected from the source of their food.
4. Longer chains increase the likelihood of food waste, as food may spoil during storage or transport.

Benefits and Trade-offs of Short Supply Chains

1. Shorter chains reduce transport emissions, storage time, and spoilage rates.
2. Farmers may receive more income, especially through farmers’ markets or direct sales.
3. Consumers may benefit from fresher food and stronger community connections.
4. However, shorter chains may limit variety, seasonality, and convenience compared to supermarkets.

Food Miles & Year-Round Supply

1. Food miles measure the distance traveled from farm to consumer, usually associated with GHG emissions from transport.
2. Globalisation allows consumers to purchase foods grown thousands of kilometres away.

Year-Round Availability and Environmental Consequences

1. Modern expectations for year-round access require:
   1. International imports from countries where the crop is currently in season.
   2. Controlled-environment agriculture (heated greenhouses).
   3. Long-term refrigeration or cold storage.
2. These practices significantly increase energy use, GHG emissions, and resource consumption.

When Local Is Not Always More Sustainable

1. Research shows that transportation often contributes less than 1% of beef’s total emissions because production itself is extremely high-impact.
2. Energy-intensive heated greenhouses can emit 10× more energy than importing the same crop from a naturally warm region.

Diet Choices: Meat, Vegetarianism & Veganism

Environmental Impacts of Meat Consumption

1. Meat, especially from ruminants, has a high environmental cost.
2. Beef and lamb production requires large amounts of land, freshwater, and fertiliser, and releases large quantities of methane.
3. Producing 1 kg of beef can require 15× more water than producing 1 kg of plant-based protein.
4. Land clearing for cattle contributes to deforestation and biodiversity loss.

Cultural Shifts in Meat Consumption

1. Wealthier societies historically show higher per capita meat consumption, as indicated by global GDP–meat consumption patterns.
2. Recent cultural shifts include:
   1. Flexitarian diets (reducing but not eliminating meat)
   2. Meatless days
   3. Growing youth-led concerns about climate change
   4. Increased awareness of animal welfare

The Rise of Veganism & Plant-Based Eating

1. Veganism is increasing globally due to concerns about climate impact, health, and ethics.
2. Plant-based diets generally:
   1. Use less land and water
   2. Produce lower GHG emissions
   3. Reduce pressure on biodiversity
   4. Improve energy transfer efficiency by eating at lower trophic levels
3. A well-balanced vegan or vegetarian diet can meet all nutritional needs with proper planning.

The Planetary Health Diet (PHD)

1. Developed by the EAT-Lancet Commission to align dietary choices with global sustainability and health needs.
2. Recommends a diet rich in:
   1. Vegetables, fruits, legumes, nuts, whole grains
   2. Moderate amounts of fish and poultry
   3. Very low amounts of red meat, dairy, refined grains and added sugars

Environmental Benefits of the PHD

1. Reduces GHG emissions, especially methane from ruminants.
2. Lowers demand for land-intensive agriculture, reducing deforestation.
3. Encourages farming systems that support soil health, biodiversity and ecosystem stability.
4. Helps maintain global food security by ensuring food is produced within planetary boundaries.

Carbon Footprint Differences Across Food Types

1. Producing 1 kg of beef emits approximately 99 kg CO₂-equivalent.
2. Lamb emits around 40 kg CO₂-equivalent.
3. Poultry emits around 10 kg CO₂-equivalent.
4. Peas emit 0.8–1.0 kg CO₂-equivalent per kg, much lower than animal proteins.
5. Transport contributes significantly less than production for most foods, except when food is transported by air.

How Diet Choices Influence Global Agriculture

1. Dietary demand determines what farmers choose to produce, influencing land use, fertiliser use, biodiversity loss and emissions.
2. Shifting consumer demand toward lower-impact foods can reshape entire agricultural systems.
3. Reducing global meat consumption would reduce the pressures on land and water, helping maintain planetary carrying capacity.

Sustainability Implications of Dietary Shifts

1. Reduced red meat consumption lowers methane emissions.
2. Increased plant-based diets encourage crop diversification, soil regeneration and reduced fertiliser demand.
3. Local and seasonal eating reduces pressure on high-energy greenhouse agriculture and long-distance imports.
4. Balanced, culturally appropriate diet shifts are essential for equitable food transitions.