Thursday, July 21, 2011

Climate impact of different foods

Earlier this week, the Environmental Working Group, a research and lobby group in DC, released a report on the “environment” and "health" impact of different foods. It found that lamb is the worst offender, followed by grain-fed beef, pork, cheese and farmed salmon.

The report was brought to my attention by a writer at the Huffington Post, who subsequently published this story which includes thoughts on the report a number of outside experts on the issue. I commented on the climate impacts of feed production and the logic of farming top-of-the-food chain fish like salmon, both issues that have been discussed frequently here at Maribo.

Here's a more complete list of my thoughts upon examining the short report:

1. “Environmental” impact or “health” impact can be very different than “climate” impact. For example, I’d expect lamb to be much lower on a list based purely on greenhouse gas emissions (i.e. per gram of food produced). I can't comment on "health" impacts as it is not my area of expertise.

2. What I call the “land use cascade” is potentially the largest contributor of greenhouse gas emissions from food production, but also the hardest to calculate. That’s why GHG emissions from dairy relative to beef cattle tend to be overestimated (more methane from dairy cattle, more land required to grow feed for beef than dairy products). It’s also why any study like this should have large positively skewed error bars.

3. All meat is not created equal in terms of greenhouse gases. Grain-fed beef is far less efficient than pork, which is again far less efficient than poultry.

4. If your food choices are motivated purely by concern about greenhouse gas emissions, eating less grain-fed beef is more important than eating locally.

5. Historically-speaking, we are just starting to develop industrial-scale farming of fish, as discussed in the recent Time cover story. Farming the ocean is, in a sense, thousands of years behind farming on land. Right now, many of the choices we are making are, as I put bluntly in the Huffington Post story, “stupid”. Cattle are logical choice for farm animals. They eat grass, so they are only one step away from the sun. Salmon are much higher up the food chain. That’s why many of us say farming salmon is like farming wolves or tigers – you need the whole ecosystem to support the one salmon.

No comments: