SAN FRANCISCO (AP) -- The world likely can't keep global warming to a relatively safe minimum unless we change how we grow, eat and throw away our food but we don't need to all go vegan, a new study says.
Researchers looked at five types of broad fixes to the food system and calculated how much they fight warming. They found that sampling a buffet of partial fixes for all five, instead of just diving into the salad bar, can get the job done, according to a study published in Thursday's journal Science.
If the world food system keeps on current trajectories, it will produce near 1.5 trillion tons of greenhouse gases over the next 80 years, the study found. That's coming from belching cows, fertilizer, mismanaged soil and food waste. That much emissions — even if the globe stops burning fossil fuels which produce twice as much carbon pollution as food — is enough to likely warm Earth by more than the goals set in the 2015 Paris climate accord.
"The whole world doesn't have to give up meat for us to meet our climate goals," said study co-author Jason Hill, a biosystems engineering professor at the University of Minnesota. "We can eat better, healthier foods. We can improve how we grow foods. And we can waste less food."
The researchers from the United States and the United Kingdom found:
• A nearly complete switch to a plant-rich diet around the world could slash almost 720 billion tons of greenhouse gases.
• If almost everyone ate the right number of calories based on their age, around 2,100 calories a day for many adults, it would cut about 450 billion tons of greenhouse gases.
• If farming got more carbon efficient -- by using less fertilizer, managing soil better and doing better crop rotation — it would slice nearly 600 billion tons of greenhouse gases.
• If farms could increase yield through genetics and other methods, it would trim almost 210 billion tons of greenhouse gases.
• If people waste less food either on their plates, in restaurants or by getting it to people in poorer countries, that would eliminate nearly 400 billion tons of greenhouse gases (360 billion metric tons).
Or, if the world does each of those five things but only half way, emissions would plummet by almost 940 billion tons. And that, with fossil fuel emissions cuts, would give the world a fighting chance of preventing another 0.5 to 1.3 degrees of warming, which the Paris accord aims to do, the study found.
Hans-Otto Poertner, who leads the United Nations science panel looking at world climate change impacts, said the study makes sense in laying out the many paths to achieving the needed emission reductions.
"There are many innovations that are possible with stopping food waste as well as stopping unsustainable practices such as cutting tropical forests for soy production and its export as (animal) feed," said Poertner, who wasn't part of the study. "It cannot be ignored that reducing meat consumption to sustainable levels would be important."
A Mediterranean diet of less meat and animal fats, along with cutting portions, would do the trick and make people healthier, Hill said.
"Something like convincing the whole world to go vegan was always going to be an impossible large sell,'' said Breakthrough Institute climate director Zeke Hausfather, who wasn't part of the study. "This paper shows that a mix of different behavioral and technological solutions can make a real difference."
While most of the world's heat-trapping gases come from the burning of coal, oil and natural gas, one-quarter to one-third of the greenhouse gases come from agriculture, Hill said.
John Roy Porter, a professor of agriculture at the University of Montpellier in France, said some of the calculations from Hill's study double counted emissions, which Hill disputes, and said he worried that "the only people really to profit from such a paper will be the fossil fuel lobby who can divert attention from oil wells to farmers' fields."
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