How our diet could become more climate-friendly

According to a study, by the year 2100, the supply of food to people could contribute 0.9 degrees to global warming. This value can be reduced by around 0.5 degrees with targeted measures, reports a research team led by Catherine Ivanovich from Columbia University in New York City in the journal "Nature Climate Change".

The scientists had analyzed current research results and their own model calculations. "Agriculture may be responsible for about 15 percent of current warming," they write.

They complain that because of the usual conversion of all greenhouse gases into equivalents of carbon dioxide (CO₂), the effect of the individual greenhouse gases is not recorded precisely enough. This applies above all to methane, almost half of which comes from agriculture. Although methane is largely degraded in the atmosphere after 10 years, it is more than 100 times more effective as a greenhouse gas than CO₂. Because CO₂ equivalents are usually calculated for a time horizon of 100 years, the short-term greenhouse potential of methane is underestimated, write Ivanovich and colleagues.

The research team extracted 206 estimates of the greenhouse gas potential of the food supply from current specialist literature. The scientists grouped 94 foods into twelve groups. They assumed that the world population will increase to almost 10 billion by 2050. Of the 50 computer simulations for the years 1765 to 2100, 29 included pathways associated with maintaining current dietary patterns and 21 pathways involving mitigation of greenhouse gas emissions. The calculations were made individually for the greenhouse gases CO₂, methane and nitrous oxide.

The authors of the study come to the conclusion that methane contributes around 60 percent to global greenhouse gas emissions from the food supply; for CO₂ and nitrous oxide it is almost 20 percent each. Methane is mainly produced by the metabolism of ruminants - especially cattle - and by rice cultivation. In agriculture, nitrous oxide emissions are mainly caused by the use of artificial fertilizers. For the year 2030, the research group determined that in the food sector, meat from ruminants will contribute 33 percent, rice 23 percent, dairy products 19 percent and meat from non-ruminants nine percent of greenhouse gas emissions.

"However, there is significant potential for emission reductions through available changes in production practices, consumption patterns, and food losses and waste," the team writes. A more climate-friendly production of meat, dairy products and rice alone could help save about a quarter of the forecast temperature increase of 0.9 degrees.

Another promising measure is the implementation of scientific nutritional recommendations in the world population, such as a low consumption of beef and a moderate consumption of fish, poultry and eggs. Further measures are the targeted climate-neutral energy supply by 2050 and a 50 percent reduction in today's food waste. Taken together, the projected warming could be reduced by 0.5 degrees by 2100 – the increase would then be 0.4 degrees instead of 0.9 degrees.

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