By the year 2100, providing people with food could contribute up to 0.9 degrees Celsius to global warming. “Agriculture may be responsible for about 15 percent of current warming,” they write Catherine Ivanovich from Columbia University in New York City and three colleagues in the journal NatureClimate Change. Nevertheless, this value can be reduced by about 0.5 degrees with targeted measures, reports the group, which analyzed current research results and its own model calculations.
In its article, the team criticizes the fact that due to the usual conversion of all greenhouse gases into equivalents of carbon dioxide (CO₂), the mode of action of the individual greenhouse gases is usually not recorded precisely enough. This applies above all to methane, almost half of which comes from agriculture. The gas is produced, for example, in the digestive tract of ruminants and is released into the atmosphere when they regurgitate a portion of feed in order to chew it again. Although methane is largely degraded in the atmosphere after ten years, by then 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 potential for saving greenhouse gases through the correct use of food is great
The team extracted 206 estimates of the greenhouse gas potential of the food supply from current literature. They grouped 94 foods into twelve groups. They assumed that the world population will grow to almost ten billion people by 2050 and calculated the greenhouse gas potential for these general conditions individually for the gases CO₂, methane and nitrous oxide.
The authors of the study come to the conclusion that methane gas alone contributes around 60 percent to global greenhouse gas emissions from the food supply; for carbon dioxide and nitrous oxide it is around 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, the production of 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 reducing emissions through available changes in production practices, consumption patterns and food losses and waste,’ the scientists write. A more climate-friendly production of meat, dairy products and rice alone could reduce the forecast global temperature increase by a quarter.
A measure that also promises success would be the enforcement of scientific nutritional recommendations in the world population, including a low consumption of beef and a moderate consumption of fish, poultry and eggs. Further measures are therefore the climate-neutral energy supply decided by the EU, which is aimed at by 2050, and a reduction of today’s food waste by 50 percent. All this taken together could reduce the projected warming by 0.5 degrees by the year 2100 – the increase would then be only 0.4 degrees Celsius instead of possibly around 0.9 degrees due to global food production.