The climate impact of food is measured in terms of greenhouse gas emissions intensity. The emissions intensity is expressed in kilograms of “carbon dioxide equivalents” – which includes not only CO2 but all greenhouse gases – per kilogram of food, per gram of protein or per calorie.
Animal-based foods, especially red meat, dairy, and farmed shrimp, are generally associated with the highest greenhouse gas emissions. This is because:
- Meat production often requires extensive grasslands, which is often created by cutting down trees, releasing carbon dioxide stored in forests.
- Cows and sheep emit methane as they digest grass and plants.
- The cattle’s waste on pastures and chemical fertilizers used on crops for cattle feed emit nitrous oxide, another powerful greenhouse gas.
- Shrimp farms often occupy coastal lands formerly covered in mangrove forests which absorb huge amounts of carbon. The large carbon footprint of shrimp or prawns is mainly due to the stored carbon that is released into the atmosphere when mangroves are cut down to create shrimp farms.
Plant-based foods – such as fruits and vegetables, whole grains, beans, peas, nuts, and lentils – generally use less energy, land, and water, and have lower greenhouse gas intensities than animal-based foods.