by Simon Donner, Canadian scientist and writer based at Princeton University
There’s a lot of chatter today about the role of meat consumption in climate change. The UN entered the fray last year with a report estimating that livestock are responsible for 18% of the world’s greenhouse gas (GHG) emissions, more than the total for all forms of transportation. It is, at first glance, hard to accept. But the UN estimate is, if anything, rather conservative.
Agriculture is truly a planetary force. More than 40% of the ice-free land is devoted to growing food for people. Feeding the animals that feed us is the primary use of much of that land. There are literally billions of cattle, pigs and chicken out there. Here’s a quick and dirty illustration: by my calculations, the world’s livestock produce 308 million kg, the weight of Empire State Building, of manure every two hours.
The problem is that in equating that livestock, animal agriculture, meat production, whatever you call it, does not fall into one GHG emissions category. The cattle themselves emit a lot of greenhouse gases, in the form of the powerful gases methane and nitrous oxide. Then, you have the emissions from the clearing of forest and grasslands so animals can graze. Next, there are all the upstream emissions from operating the slaughterhouses, the processing plants, running all the machinery and transporting everything.
The biggest source of all, however, may be all the energy and land used to grow the crops that exist only to feed livestock. More than two-thirds of the corn and soybeans grown in the US are used to feed animals, primarily beef cattle, which are the least efficient at converting animal feed (the corn) into human food (the steak).
The result is that countries that eat a lot of meat produce a lot of the world’s greenhouse gases. This graph comparing meat consumption and greenhouse gas emissions per capita (for the top 100 countries by population) illustrates the connection. There’s the US, Australia and Canada in the right corner. Argentina and Chile manage high meat consumption with low emissions by relying on grass-fed beef and imported meat from Brazil.
The graph is also a reflection of wealth. Throughout history, wealthier societies have eaten more meat and used more energy. What we have today is a complicated web. As countries in the lower left corner become wealthier, they will begin to eat more meat and produce more GHG emissions.
In order to achieve the twin goals of reducing poverty and fighting climate change, we will need to decrease the GHG emissions required to produce a gram of food protein. And that may very well mean reducing consumption of foods from low efficiency production systems, especially grain-fed beef.