The Intergovernmental Panel on Climate Change (IPCC) has urged
every individual in the developed countries to reduce the meat consumption by 50 percent by 2050, and to reduce emissions in industrial and agricultural sectors by 50 percent, to curb the most potent of greenhouse gases, nitrous oxide
The findings are results of a study by Dr. Eric Davidson and
are published today in IOP Publishing's Environmental Research Letters. Dr.
Davidson, who is President and a Senior Scientist at the Woods
Center in Massachusetts, demonstrates the magnitude of
changes needed to stabilize N2O concentrations in the atmosphere.
N2O is the third highest contributor to climate change
behind carbon dioxide (CO2) and methane (CH4); however, it poses a greater
challenge for mitigation since nitrogen is an essential element for food
production. It is also the most potent of these three greenhouse gases, as it
is a much better absorber of infrared radiation. But total anthropogenic
emissions are about 6 million metric tons of nitrogen as N2O, compared to 10
billion metric tons of carbon as CO2.
The main sources of N2O in the atmosphere are due to the
spreading of synthetic nitrogen fertilizers onto agricultural soils and the use
and storage of livestock manure. The nitrogen contained in fertilizers and
manure is broken down by microbes that live in the soil and released into the
atmosphere as N2O. In order to reduce emissions, it will be necessary to apply
certain changes to the food production process.
Dr. Davidson believes that this can be achieved through
improved management of fertilizer and manure sources, as well as through
reduction of the developed world's per capita meat consumption that will relieve
pressure on fertilizer demand and reduce growth in the amount of manure being
produced. "We have the technical know-how and the tools to greatly improve
efficiencies of fertilizer use in agriculture," states Davidson, "although
several economic and political impediments often stand in the way of their
In a draft of the IPCC's Fifth Assessment Report, four
scenarios, known as representative concentration pathways (RCPs), have been
adopted, and these represent possible means of reductions for a number of
greenhouse gases. Dr. Davidson evaluated the scale of changes needed to meet
the predicted N2O pathways.
Three of the IPCC's less aggressive scenarios could be met
by reducing meat consumption, improving agricultural practices, or reducing
emissions from industry. The most aggressive scenario, where atmospheric N2O
concentrations stabilize by 2050, can only be met if a 50 percent reduction, or
improvement, is achieved for each of the above.
To make these calculations, Dr. Davidson relied on data
provided by the Food and Agricultural Organization, which assume that the
global population will increase to 8.9 billion by 2050 and the daily calorific
intake per capita will increase to 3130 kcal. They also assume that the average
meat consumption of each person in the developed world will rise from 78 kg per
year in 2002 to 89 kg per year in 2030 and from 28 kg per year in 2002 to 37 kg
per year for each person in the developing world.
Assessing the likelihood of reducing meat consumption in the
developed world by 50 percent, Davidson said, "If you had asked me 30 years ago
if smoking would be banned in bars, I would have laughed and said that would be
impossible in my lifetime, and yet it has come true. Similarly, there would be
beneficial health benefits for most Americans and western Europeans to stop
'supersizing' and rather to reduce portion sizes of red meat."
Are such changes possible for diet? "That will depend," says
Davidson, "not only on education about diet, but also on prices of meat. Some
agricultural economists think that the price of meat is going to go way up, so
that per capita consumption will go down, but those are highly uncertain