IB Environmental systems and societies 5.2G Sustainability of Different Diets Notes

Sustainable Diets: What You Eat Matters More Than Where It Comes From

1. The sustainability of a diet depends on how food is produced, processed, transported and consumed, making it an environmental, social and economic issue at once.
2. Key factors include supply chain length, farming techniques, food miles, and shifts in eating habits.
3. A sustainable diet aims to meet nutritional needs while limiting harm to ecosystems, climate, biodiversity and resources.

Supply Chains: More Intermediaries Mean More Impact

1. A supply chain covers every stage from production to processing, packaging, transport, retail and consumption.
2. Long supply chains involve multiple intermediaries, such as distributors, processors, wholesalers and retailers.
   1. Each extra stage adds energy use, emissions, packaging, refrigeration and cost.

Environmental Impacts of Long Supply Chains

1. Long supply chains raise total fuel use and CO₂ emissions, especially when refrigeration or air transport is needed.
2. Greater distance raises food miles, a measure of transport-related impact.
3. Longer chains widen social and economic distance, so less profit reaches farmers and consumers lose touch with where their food comes from.
4. Longer chains also raise the risk of food waste, as food can spoil during storage or transport.

Benefits and Trade-offs of Short Supply Chains

1. Shorter chains cut transport emissions, storage time and spoilage.
2. Farmers often earn more income through farmers' markets or direct sales.
3. Consumers gain fresher food and stronger community ties.
4. However, shorter chains can limit variety, seasonality and convenience compared with supermarkets.

Food Miles and the Cost of Year-Round Supply

1. Food miles measure the distance travelled from farm to consumer, often linked to transport GHG emissions.
2. Globalisation lets consumers buy foods grown thousands of kilometres away.

Year-Round Availability and Environmental Consequences

1. Year-round access usually relies on three energy-hungry methods.
   1. International imports from countries where the crop is in season.
   2. Controlled-environment agriculture such as heated greenhouses.
   3. Long-term refrigeration or cold storage.
2. These methods sharply raise energy use, GHG emissions and resource consumption.

When Local Is Not Always More Sustainable

1. Transport is often less than 1% of beef's total emissions, because production itself is so high-impact.
2. A heated greenhouse can use about 10 times more energy than importing the same crop from a naturally warm region.

Diet Choices: Why Meat, Especially Ruminants, Costs More

Environmental Impacts of Meat Consumption

1. Meat, especially from ruminants like cattle and sheep, has a high environmental cost.
   1. Beef and lamb need large amounts of land, freshwater and fertiliser, and cattle and sheep release methane as they digest.
   2. Producing 1 kg of beef can use about 15 times more water than 1 kg of plant protein.
   3. Clearing land for cattle drives deforestation and biodiversity loss.

Cultural Shifts in Meat Consumption

1. Wealthier societies have tended to eat more meat per person, a pattern seen in global GDP and meat-consumption data.
2. Several recent cultural shifts are pushing the other way.
   1. Flexitarian diets that reduce but do not cut out meat.
   2. Meatless days built into the week.
   3. Youth-led climate concern driving lower-meat choices.
   4. Animal-welfare awareness shaping what people buy.

The Rise of Veganism and Plant-Based Eating

1. Veganism is growing worldwide over concerns about climate, health and ethics.
2. Plant-based diets generally bring four benefits.
   1. Lower land and water use than animal products.
   2. Lower GHG emissions per unit of food.
   3. Less pressure on biodiversity from farming.
   4. More efficient energy use from eating at lower trophic levels.
3. A well-planned vegan or vegetarian diet can meet all nutritional needs.

The Planetary Health Diet: Eating Within Planetary Boundaries

1. The EAT-Lancet Commission developed the diet to align food choices with global health and sustainability.
2. It recommends a clear balance of food types.
   1. Plenty of vegetables, fruits, legumes, nuts and whole grains.
   2. Moderate fish and poultry.
   3. Very little red meat, dairy, refined grains and added sugar.

Environmental Benefits of the PHD

1. Cuts GHG emissions, especially methane from ruminants.
2. Lowers demand for land-intensive farming, reducing deforestation.
3. Supports farming that protects soil health, biodiversity and ecosystem stability.
4. Helps keep food production within planetary boundaries, supporting food security.

Carbon Footprints: Beef and Peas Are Worlds Apart

1. Beef emits about 99 kg CO₂-equivalent per kg produced.
2. Lamb emits around 40 kg CO₂-equivalent per kg.
3. Poultry emits around 10 kg CO₂-equivalent per kg.
4. Peas emit just 0.8 to 1.0 kg CO₂-equivalent per kg, far below animal proteins.
5. For most foods, production matters far more than transport, except when food is flown by air.

How Diet Choices Reshape Global Agriculture

1. Dietary demand decides what farmers produce, shaping land use, fertiliser use, biodiversity loss and emissions.
2. Shifting demand toward lower-impact foods can reshape whole agricultural systems.
3. Eating less meat eases pressure on land and water, helping protect planetary carrying capacity.

Sustainability Implications of Dietary Shifts

1. Eating less red meat lowers methane emissions.
2. More plant-based eating supports crop diversity, soil regeneration and less fertiliser use.
3. Local, seasonal eating eases pressure on high-energy greenhouse farming and long-distance imports.
4. Balanced, culturally appropriate shifts are essential for fair food transitions.