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Here’s exactly how your diet affects the planet, a new study finds

Here’s exactly how your diet affects the planet, a new study finds

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Eco-friendly eaters may know that almonds are a water-intensive crop, that fish farms pollute the water or that beef consumption drives deforestation. But a study released Monday goes far broader and deeper, offering a new guide to weighing total ecological consequences of crops, livestock and seafood.

Researchers amassed data on food production and its impacts on the Earth including disturbances to wild-animal habitats, water use and pollution, and contribution to planetary warming. Their findings reveal what types of food production have the greatest consequences, and where.

The study published in the journal Nature Sustainability — which examined nearly 99 percent of all food production on land and sea as reported to the United Nations in 2017 — offers a new way to evaluate what to eat and how to feed the world, according to its lead author, Ben Halpern, a professor at the University of California at Santa Barbara.

“We need to be thinking about the multiple ways that food affects the environment,” said Halpern, who directs UCSB’s National Center for Ecological Analysis and Synthesis. “The results we’ve presented show how you can use more information about these multiple stressors and the global scale of our food production consequences to influence your individual choice.”

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The researchers left out food produced in home gardens and by hunters, as well as nonfood crops like coffee, tea and tobacco. But they assessed impacts including displacing ecosystems for cropland and destroying seafloor habitat with fishing equipment; water used by crops and livestock; nutrient pollution of waterways from fertilizer-tainted runoff and concentrated fecal matter; and greenhouse gas emissions from farming machinery and boat engines, production of fertilizers and pesticides, and livestock flatulence and manure.

Pigs and cattle rank as the top environmental offenders

Unsurprisingly, pig and cattle meat ranked far ahead of any other products, with cattle having a massive impact on greenhouse gas emissions and pigs on water quality. But pork may have larger environmental costs than beef when factoring in that so much pig waste ends up polluting waterways.

Nutrient pollution from animal waste and fertilizers causes algae blooms in waterways, which can eventually create “dead zones” of water containing little or no dissolved oxygen.

The researchers also included the environmental impact of any plant or other animal used to produce feed for livestock and fish, which boosted the overall damage associated with these kinds of foods.

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Seafood affects the land, not just the ocean

The study raises questions about the sustainability of seafood, finding that it has an outsize impact on shore as well as off our coasts. While aquatic systems produce 1.1 percent of the world’s food, they account for 9.9 percent of the food system’s global environmental footprint.

A category of fish that includes cod, flounder and halibut had more than four times the environmental impact of other fish because the trawls dragged to harvest them destroy habitat along the seafloor. The environmental pressure was three times that associated with raising sheep for meat, though that type of fishing produces four times more food than sheep farming does, the study noted.

One researcher not involved with the study said its approach provides a “comprehensive” analysis that goes far beyond other work to quantify environmental pressures, with most looking strictly at land- or sea-based impacts, and not both.

“The authors had to make some difficult choices about how they’d compare apples to oranges, and while their attempt was not the final word of that conversation, it represents an important start,” said Matthew Hayek, an assistant professor in environmental studies at New York University.

Rice, wheat and other crops’ magnified impact

Rice and wheat ranked in the same tier of environmental impacts as animal-based products including cow milk and chicken meat largely because growing the grains requires so much water. But also, they are grown in such massive quantities around the world that their disturbances to natural habitats and ecology are magnified.

Crops used to make cooking oils, including palm and canola, are other examples of plant-based food products whose impacts rival those of some animal-based products because they are grown and used so widely, the study found.

On the other hand, a crop like papaya is particularly resource intensive, but it is grown on such a relatively smaller scale that its impact is low, Halpern said.

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Five countries account for half of the globe’s food footprint

Five countries account for nearly half of all food system impacts: India, China, the United States, Brazil and Pakistan.

And researchers found that not only was this damage heavily concentrated in a handful of countries, but that some countries have bigger environmental impacts than others for producing the same types of food.

For example, beef production in Brazil has a larger environmental impact than is attributed to the U.S. cattle industry, though Brazil produces 10 percent less meat than the United States.

Halpern said he hopes the study leads more people and policymakers to consider ways to reduce the environmental consequences of food choices and regulation. Though the analysis considers the different types of ecological pressures equally, future use of the data and research methods could weigh one more heavily depending on what environmental challenges are being faced, he said.

“There’s so many possible solutions to reducing the environmental footprint of food production,” Halpern said. “We have created a huge menu for options of how to do that.”

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