Given the latest report from the new dietary guidelines committee that recommends less meat eating (see some of my previous discussion on that here), I found this study just published in Ecological Economics by Janina Grabs quite interesting.
Grabs ask an important question that is rarely asked. If people stop spending money on meat, what will they spend their money on instead? And, what are the environmental impacts of those other non-meat expenditures? Using data based on Swedish consumers, she calculates that, at first blush, a vegetarian diet does indeed appear to have slightly smaller energy use and carbon impacts, BUT if you take into consideration what the vegetarians do with the extra money they used to spend on meat, those environmental gains become dramatically smaller. She calls this the rebound effect.
Here's the abstract:
A couple caveats. First, it is important to notice an important clause to sentence claiming a 16% reduction in energy use and 20% reduction in greenhouse gas emissions - this is the reduction related only to their diet. In terms of overall impact, I believe these only translate to 1.8% and 4.15% reductions, quite simply because food only makes up a small part of the consumers overall energy use and carbon impact. Of course, all this relates to the "first round" impacts and ignores the rebound effect, which is the main point of this study.
Second, the later part of the abstract, which suggests that the, "adverse effect could be tempered by purchasing organic goods" is mainly due (if I'm understanding the study correctly) to an income effect NOT because organics have substantively less energy/carbon impacts. Because organics cost more, that leaves less money for the consumer to spend on other things that would require energy. You could create the exact same kind of result by simulating a person who bought and ate less food, and then took all the dollar bills that were saved, and burned them. This little thought experiment ought to reveal that the goal in life is not to minimize energy use per se, only to reduce it to the extent that you're not taking into account the impacts on others that are not already reflected in the market price.
None of that should distract from the overall important message of this study: that we need to look at all the effects (even unintended ones) when trying to look at policies that encourage people to change dietary habits.