Researchers at Oxford University and the Swiss agricultural research institute, Agroscope, have created the most comprehensive database yet on the environmental impacts of nearly 40,000 farms, and 1,600 processors, packaging types, and retailers. This allows them to assess how different production practices and geographies lead to different environmental impacts for 40 major foods.

They found large differences in environmental impact between producers of the same product. High-impact beef producers create 105kg of CO2 equivalents and use 370m2 of land per 100 grams of protein, a huge 12 and 50 times greater than low-impact beef producers. Low-impact beans, peas, and other plant-based proteins can create just 0.3kg of CO2 equivalents (including all processing, packaging, and transport), and use just 1m2 of land per 100 grams of protein.

Aquaculture, assumed to have relatively low emissions, can emit more methane, and create more greenhouse gases than cows. One pint of beer can create 3 times more emissions and use 4 times more land than another. This variation in impacts is observed across all five indicators they assess, including water use, eutrophication, and acidification.

'Two things that look the same in the shops can have extremely different impacts on the planet. We currently don’t know this when we make choices about what to eat. Further, this variability isn’t fully reflected in strategies and policy aimed at reducing the impacts of farmers,' says Joseph Poore from the Department of Zoology and the School of Geography and Environment.

'Agriculture is characterised by millions of diverse producers. This diversity creates the variation in environmental impact. It also makes finding solutions to these environmental issues challenging. An approach to reduce environmental impacts or enhance productivity that is effective for one producer can be ineffective or create trade-offs for another. This is a sector where we require many different solutions delivered to many millions of different producers.'

These graphs show environmental impacts for 9 animal and 6 vegetable products from a sample of ~9,000 farms around the world. Results for a further 25 food products covering ~30,000 farms, as well as results for water use are provided in the study.

For producers, the researchers present evidence in favour of using new technology. This technology often works on mobile devices, taking information on inputs, outputs, climate, and soil, to quantify environmental impacts. The technology then provides recommendations on how to reduce these impacts and increase productivity.

However, producers have limits on how far they can reduce their impacts. Specifically, the researchers found that the variability in the food system fails to translate into animal products with lower impacts than vegetable equivalents. For example, a low-impact litre of cow’s milk uses almost two times as much land and creates almost double the emissions as an average litre of soymilk.

Animal product free diets, therefore, deliver greater environmental benefits than purchasing sustainable meat or dairy.

Further, without major changes in technology that disproportionately target animal products, the researchers show that animal product free diets are likely to deliver greater environmental benefits than changing production practices both today and in the future.

Specifically, plant-based diets reduce food’s emissions by up to 73% depending where you live. This reduction is not just in greenhouse gas emissions, but also acidifying and eutrophying emissions which degrade terrestrial and aquatic ecosystems. Freshwater withdrawals also fall by a quarter. Perhaps most staggeringly, we would require ~3.1 billion hectares (76%) less farmland. 'This would take pressure off the world’s tropical forests and release land back to nature,' says Joseph Poore.

The researchers show that we can take advantage of variable environmental impacts to access a second scenario. Reducing consumption of animal products by 50% by avoiding the highest-impact producers achieves 73% of the plant-based diet’s GHG emission reduction for example. Further, lowering consumption of discretionary products (oils, alcohol, sugar, and stimulants) by 20% by avoiding high-impact producers reduces the greenhouse gas emissions of these products by 43%.

This creates a multiplier effect, where small behavioural changes have large consequences for the environment. However, this scenario requires communicating producer (not just product) environmental impacts to consumers. This could be through environmental labels in combination with taxes and subsidies.

'We need to find ways to slightly change the conditions so it’s better for producers and consumers to act in favour of the environment,' says Joseph Poore. 'Environmental labels and financial incentives would support more sustainable consumption, while creating a positive loop: Farmers would need to monitor their impacts, encouraging better decision making; and communicate their impacts to suppliers, encouraging better sourcing.'

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