On Earth Day two weeks ago, 171 countries officially signed the Paris Agreement on climate change. In doing so, they agreed to the long term goal of ending humanity’s damage to the climate—that is, reducing our emissions of global warming pollution to zero—in the second half of this century. One encouraging part of the ongoing scientific discussion about how to achieve this ambitious goal, is that we’re finally starting to take seriously the impact of what people eat. Three recent studies show that it makes a big difference, to the climate as well as to our health.

As I’ve written before—in this blog, in UCS reports and in the scientific journal Nature Climate Change—by far the biggest impact of diet on climate comes from eating high on the food chain by consuming lots of meat – but not just any meat. What really makes a difference is the amount of beef. This point is made clearly in a graphic from one of the new studies, published by Janet Raganathan and colleagues in a chapter of the annual IFPRI Global Food Policy Report, and in longer form as a report from the World Resources Institute:

The orange bars are the ones showing the climate impact (amount of greenhouse gas emissions) of different ways of getting the protein we need. As you can see, beef (the far right-hand column) has by far the largest effect, not only compared to plant sources but also relative to other kinds of meat.

Based on this and other data, Raganathan et al. modeled the impact of reducing global beef consumption by a third. The cuts were targeted to global “overconsumers” – roughly speaking, the fourth of humanity that eats more protein than necessary and/or high per-capita quantities of beef. Of course, this includes most Americans.

They not only found that diet changes by these people could achieve a substantial reduction in emissions, but also that the effect was nearly identical whether beef was replaced in the diet by “pulses” (leguminous plants like peas, beans and soy) or by poultry and pork. You can see the underlying reason for this in the graph above – compared to beef, all these foods cause much less global warming pollution.

A caveat here is that these studies obviously take into account the beef production systems that already exist, and those systems could be improved. A report by Richard Teague and colleagues in the Journal of Soil and Water Conservation highlights the role of environmental services (such as reduced soil erosion) offered in grassland environments. Improved grassland management in beef production could be paired with an overall reduction in beef consumption.

Another modelling study, just published in the Proceedings of the National Academy of Sciences by Marco Springmann and colleagues, showed that such diet shifts also would save millions of lives. They modelled a different set of dietary patterns (vegan, vegetarian or “healthy”—less red meat and sugar, more fruit and vegetables) but the majority of the positive impacts—on both death rates and global warming—came from the reduction in red meat. Here’s their graphic summarizing the results, with lives saved shown in A and the change in greenhouse gas emissions shown in B. As you can see, it’s the orange sections of the bars – the reductions in red meat consumption – that make by far the biggest differences to both health and climate:

These two studies add to what is now a substantial body of research on the kinds of diet shifts that could have large benefits in terms of global warming. Indeed, there are now enough studies out there that researchers can combine and compare them all in a systematic review, and this has now been done for the literature published up through February 2014 by Elinor Hallstrom, Annika Carlsson-Kanyama and Pal Borgesson. Here are the potential reductions in emissions from different kinds of diet shifts, from their summary table:

The lessons from this summary of the science are clear: the consistently large reduction potentials come not only from vegan or vegetarian diets, but also from diet shifts that replace meat from ruminant animals (mostly beef cattle) with meat from monogastric animals (i.e. non-ruminants, mostly chicken and pigs).

Raganathan et al. discuss the kinds of social and economic changes that could lead to reductions in beef consumption among overconsumers, and point out that:

This diet shift … would be relatively easy to implement, since it only affects one type of food. Additionally, some high-consuming countries have already reduced per person beef consumption from historical highs, suggesting that further change is possible.

Commenting on the WRI study which he co-authored, Tim Searchinger of Princeton University put things straightforwardly: “The single most important thing is to eat less beef.” He’s absolutely right, but there are other ways we can make a difference too. The WRI report has a good discussion of how government and business policies affect diets, on the one hand indirectly subsidizing some foods or on the other hand insuring that we see the full cost of what we eat.

And when it comes to the deforestation caused by beef—an important part of its global warming footprint—you can tell companies that they need to go deforestation-free. Not just as consumers, but also by acting as citizens, we can all be part of the effort to end the damage to our global climate.

Over the next two months, I’ll be writing about more of the science concerning beef and its environmental impact. I’ll be doing a series of posts reviewing three different books and movies on this subject:

A quick preview: I think the first two, which are strongly anti- and pro-beef respectively, are scientifically weak. I have some criticisms of Cowed, but do give it credit for taking the science seriously. So, stay tuned!

Posted in: Food and Agriculture, Global Warming, Tropical Forests Tags: agriculture, beef, climate-change, diet, food, Global warming, meat, Tropical deforestation, vegan, vegetarian



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