1) Avoid RED MEAT & CHEESE: these cause several times more greenhouse gas emissions (per gram) than other foods . This is for 2 main reasons. Firstly, cows and sheep release methane when they burp  – this is a gas 34x more problematic than CO2 (over a 100-year period) . Secondly, red meat and cheese production use land inefficiently: per gram of protein, peas take up only 2% as much land as beef, and 8.5% as much as cheese .
Chicken produces on average only 10% as much greenhouse gas emissions as beef (per g of protein) . Peas produce just 1%, compared to beef . So, whilst vegan diets tend to have the lowest environmental impact , swapping beef for chicken can have a HUGE effect. If we didn’t eat any meat or dairy, we would only need ~25% of existing farmland to feed everyone [1,15]! In small numbers, cattle can help maintain wildlife-rich land [9,10], but given how much meat humans currently eat, free-range meat is a bad option. Why? Because it increases the total amount of land needed even more . So: avoid beef at all costs.
2) Minimise food WASTE: about a third of all food produced is thrown away . If food waste was a country, it would have the 3rd highest greenhouse gas emissions in the world ! In poor countries, we need better food harvesting and storage . Elsewhere, most waste is by consumers . So: plan your meals carefully to minimize waste !
3) Buy SEASONAL food: this means food doesn’t have to be stored so long, saving energy on powering freezers . There are lists online of fruit and veg that are in-season each month, e.g.  for the UK. Eating food that is both in season and local can help reduce your carbon footprint [3,18].
4) But: do NOT choose food based only on WHERE it was made  – minimising “food miles” could increase your carbon footprint ! This is because transport from farm to shop causes only a small proportion (4% in the USA) of the total carbon footprint of food . For example, buying local food grown in a heated greenhouse is often worse than getting it shipped in from abroad where it was grown without heating .
 Our calculations based on data S2 from Poore and Nemecek 2018: https://science.sciencemag.org/content/360/6392/987/tab-figures-data
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