The true environmental pressures of our global food system are frequently elusive and challenging to evaluate in an era of industrialised farming and complicated supply chains.
"Everyone eats food, and more and more people are paying attention to the planetary consequences of what they eat," said UC Santa Barbara marine ecologist Ben Halpern. Figuring out this impact on the planet proves to be a gargantuan task for many reasons, including the fact that around the world there are a lot of different foods produced in many different ways, with many different environmental pressures.
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Scientists have made significant progress in evaluations of the environmental impacts of food by pound or kilogramme by ranking foods on elements like greenhouse gas emissions or water pollution. While these assessments are useful in assisting consumers in making decisions, Halpern noted that for decisions that must be made in a world with a rapidly expanding population, a more thorough analysis of the environmental footprint--the areas affected by the various pressures from food production and the intensity of those pressures--is required.
"The individual choice of eight billion people adds up," he said, "and we need to know the overall impact of total food production -- not just per pound -- especially when setting food policy."
To fill that need, Halpern and colleagues at UC Santa Barbara's National Center for Ecological Analysis & Synthesis (NCEAS) have mapped for the first time the environmental footprint of the production of all foods, both in the ocean and on land. Their research is published in the journal Nature Sustainability.
Lopsided pressures and hidden connections
"Did you know that almost half of all environmental pressures from food production come from just five countries?" Halpern said.
Halpern, who serves as the executive director of NCEAS and a professor at the Bren School of Environmental Science & Management at UCSB, has a longstanding interest in understanding the effects of food production as well as the local context of these impacts. The researchers were able to produce a more nuanced picture of the pressures -- the inputs, processes, and outputs -- of global food production by taking detailed data about greenhouse gas emissions, freshwater use, habitat disturbance, and nutrient pollution (e.g., fertiliser runoff) generated by 99% of the total reported production of aquatic and terrestrial foods in 2017.
The results are startling.
"Cumulative pressures of food production are more concentrated than previously believed, with the vast majority -- 92% of pressures from land-based food production -- concentrated on just 10% of the Earth's surface," noted Melanie Frazier, a research scientist at NCEAS and coauthor of the paper. Additionally, the space required for dairy and beef farming accounts for about a quarter of the cumulative footprint of all food production. And those five countries accounting for almost half of all food production-related environmental pressures? India, China, the United States, Brazil and Pakistan.
Similar to the per-pound-of-food approach used by most other studies, the study also examines each food type's environmental efficiency, but this time it takes into account regional variations rather than assuming that it is the same everywhere.
"The environmental efficiency of producing a particular food type varies spatially, such that rankings of foods by efficiency differ sharply among countries, and this matters for guiding which foods we eat and from where," said Halley Froehlich, assistant professor in environmental studies at UCSB and a co-author of the study. The evaluation made by the research team takes production methods into account. For instance, the United States, the world's top producer of soy, is more than twice as efficient at growing the crop than India, the fifth-largest producer, thanks to technology that lowers greenhouse gas emissions and increases yields, making American soy the more environmentally-friendly option.
Additionally, the study reveals connections between land and sea that are missed when focusing on just one or the other and that have a significant impact on environmental pressures. Pigs and chicken have an ocean footprint because they are fed marine forage fish like herring, anchovies, and sardines. The opposite is true for mariculture farms, whose feeds based on crops spread the environmental pressure of fish farms onto land.
Examining cumulative pressures can reveal outcomes that cannot be foreseen by focusing only on individual pressures. The cumulative pressures of raising pigs, which produce more pollution and use more water than cattle farming, are slightly greater than those of raising cows, despite the fact that raising cattle by far requires the most grazing land. Pig, cow, rice, wheat, and oil crops are the top five offenders when measured by cumulative pressures.
According to the researchers, significant changes will need to be made to current food systems in order to feed a growing and more affluent global population, lessen environmental damage, and improve food security. In some instances, farming may need to become more efficient, while in other instances, consumers may need to alter their food preferences.
"We need this comprehensive information to make more accurate decisions about what we eat," said Halpern, who modified his own food choices based on the results of this study.
"I became a pescatarian years ago because of wanting to reduce the environmental footprint of what I eat," he said. "But then I thought, I'm a scientist, I should really use science to inform my decisions about what I eat. That's actually why I started this research project. And now that we have the results, I see that from an environmental perspective, chicken is actually better than some seafood. And so I've shifted my diet to start including chicken again, while eliminating some high-pressure seafoods like bottom-trawl caught cod and haddock. I am actually eating my words."