A member of the audience at one of my climate change slide shows asked me why I hadn’t mentioned the benefits of switching to vegetarianism when it comes to things we can do to lower our carbon footprint. I replied that I thought eating less meat will be as much as consequence of our actions as a way to change them.
It’s not that I disagreed with the premise that meat production consumes too much energy and water, resources that could be better used to grow more plants. That’s inarguable. It’s just that I see enormous resistance among North Americans and Europeans to the idea of voluntarily eating less meat, more resistance even than to giving up the personal automobile. Sooner I later, it will just make no sense to waste resources raising cows, I reckoned, and society will reduce its meat production because it has to as the world heads toward 9 billion people.
But the scientific calculations behind the argument in favor of giving up meat are become hard to ignore. There’s a new paper in the journal Climate Change: “Climate benefits of changing diet” by Elke Stehfest and colleagues at the Netherlands Environmental Assessment Agency and Wageningen University Research that comes to some dramatic conclusions.
I strongly suspect at least some of the authors are vegetarians, what with language like:
Dietary changes may not only be attractive from a climate perspective, the impacts they might have on human health and life expectancy are also of great interest from a public health perspective.
But I don’t know and don’t much care. What’s important is the rigor of the analysis. And the paper seems to take a comprehensive look at the issues involved. Stehfest et al write that the net decrease in land required for agriculture if we mostly eliminate livestock from the industry means that there will be a lots of land reverting to forests and other carbon sinks, sinks that will go a long way toward keeping greenhouse-gas concentrations down to 450 ppm of CO2e.
[Some believe that won't be low enough and that we need to be closer to 350 ppm, but whatever the ultimate target, it would be foolish to ignore any strategy that could help us get us to wherever we need to go.]
They sketch out four possible pathways to effect the kind of change they suspect is necessary. There’s the No Ruminant (basically four-legged) Meat, No Meat, No Animal Products scenarios and Healthy Diet (some meat, more fish, etc) scenarios. It’s not immediately obvious which will produce the best result, as replacing milk with plant proteins, for example, leads to an increase in cropland, rather than a reduction. But:
The largest reduction of greenhouse gas emissions by product category is caused by the substitution of ruminant meat, with a large terrestrial net CO2 sink of about 30 GtC over the whole period compared to a net source of 34 GtC in the reference case
There are plenty of opportunities to bias the calculations in one direction or another. Stehfest et al are up front about the uncertainties involved when trying to generate scenarios that makes sense. They write, for example, that
The pace at which natural vegetation recovers on abandoned agricultural land is another important uncertainty. As described above, the time needed for reaching maximum net primary production ranges from 2 years for grasslands to 20 years for boreal forest (van Minnen et al. 2000). In a sensitivity run, this recovery time was increased by a factor of 2. A further important uncertainty is the effect that drastic demand changes may have on the agricultural system. In the variants, we had assumed that crop yields are identical to those in the reference case. However, a decreasing demand and a subsequent decrease in land prices is likely to slow down the improvement of agricultural technology and crop yields. And even more directly, the abandonment of vast areas of pasture and cropland for feed production may lead to extensification of the remaining agriculture.
The real Achilles heel of this kind of research, research that addresses the relative financial cost of mitigation as well as the physical consequences of particular strategies, is that predicting effects on human actions is pretty well impossible to do to any degree of confidence. As the authors admit, “we have ignored possible socio-economic implications such as the effect of health changes on GDP and population numbers.”
Getting back to my original approach to the chicken-or-egg question of the relationship between meat and climate change, here’s one last excerpt, this time from the paper’s closing discussion:
An interesting question is what kind of potential strategies could lead to lower consumption of meat, eggs and milk. While some authors have recently suggested reducing meat consumption via a special tax, others stress that no large changes can be expected through price mechanisms…. Nevertheless, the benefits of dietary change to both health and climate mitigation and the feasibility of low stabilization targets as shown here are important enough to put this issue on the political agenda.
Food for thought, indeed.
Elke Stehfest, Lex Bouwman, Detlef P. Vuuren, Michel G. J. Elzen, Bas Eickhout, Pavel Kabat (2009). Climate benefits of changing diet Climatic Change DOI: 10.1007/s10584-008-9534-6