Tag Archives: veganism

Diet and Climate Change

In their 2009 study in Climatic Change, Stehfest et al. pointed out that “climate change mitigation policies tend to focus on the energy sector, while the livestock sector receives surprisingly little attention, despite the fact that it accounts for 18% of the greenhouse gas emissions and for 80% of total anthropogenic land use.” As many begin to realize the significance of agriculture-based emissions and contributions to climate change, researchers are increasingly studying this topic. Though this is definitely a very recent trend, I was able to find several studies from the last ten years which focus on the connection between dietary choices and future climate change. You can find these studies and more at the end of this post, if you want to read their abstracts and understand them more deeply. The basic idea behind all the studies is the same. They use measured demographic and agricultural trends (for example agricultural yields, dietary choices, population growth, wealth, etc.) to create a model which contains the many variables that together define our current food system. Researchers can then run different theoretical future scenarios through the model and find the resultant greenhouse gas (GHG) emissions of each scenario. Different scenarios assume certain changes to the current food system, such as reduced meat consumption or yield increases. See the figure below for an example of Stehfest et al.’s results.

Screen Shot 2015-02-02 at 3.20.43 PM

The above chart shows global GHG emissions in the year 2050, measured in gigatonnes CO2 equivalent. (A gas such as CH4 has a different Global Warming Potential (GWP) from CO2, based on its heat-trapping ability and lifetime in the atmosphere; the number graphed here is the estimated amount of CO2 equivalent to that of all GHGs emitted, based on GWP calculations for various gases such as CH4 and NO2.)

Each of the bars shown above represents a different future scenario. REF is the reference scenario in which all current trends continue. This could be thought of as the control. Scenario IP is based on widespread improvement in productivity. TM includes this productivity improvement as well as the adoption of specific emission mitigation technologies such as adding fat to cattle feed, which decreases the amount of CH4 cows emit during digestion. The CC, or Climate Carnivore scenario assumes that worldwide 75% of ruminant meat and dairy products are replaced by other animal products (in addition to the steps taken in IP and TM). Ruminant animal products (those derived from ruminants such as cattle, sheep, and goats) have inherently higher GHG emissions because these animals digest the cellulose in their food by way of fermentation, which produces the potent greenhouse gas CH4 as a byproduct. This explains the large reduction in emissions from the CC scenario. Finally, the FL or Flexitarian scenario assumes that 75% of animal products are replaced by plant-based sources (once again, in addition to IP and TM improvements).

As you can clearly see, the FL scenario, in which the least animal products are consumed, results in the lowest agriculture-based GHG emissions of all situations. As authors Hedenus et al. explain, “deep cuts in emissions from food and agriculture do not seem plausible without large changes in consumption towards less GHG intensive food, in particular less ruminant meat and dairy.” What I find fascinating here is the significance of the emissions reduction from simply decreasing consumption of ruminant products. I think this is encouraging for those who can see the value in eating fewer animal products, but are not able to change their diet drastically because of certain limiting factors. If we all made the effort to eat less beef and milk, the climate would be measurably better off.

In a similar study, authors Bajželj et al. asserted that “only when strategies include significant elements of demand reduction is it possible to prevent an increase in agricultural expansion and agriculture-related GHG emissions.” The emphasis here is on managing agriculture-based emissions from the demand side of the food chain rather than (or in addition to) the supply side, i.e. changing diets rather than changing agricultural methods. Agriscience research is focused almost completely on increasing yields and this effort is no doubt important, as the researchers acknowledge. However, there are “biophysical limits” on yields and we cannot continue to increase these forever. For this reason and many others, it is valuable and necessary to change the demand side of the food chain. This means changing our diet and eating less animal products. See below for a visualization of the findings of this study.


In the above chart, Bajželj et al. compare the emissions (in gigatonnes COequivalent per year) resulting from agriculture and land use change in six different scenarios. Every CT scenario assumes the continuation of Current Trends in yield increases. Every YG scenario is based on a worldwide closing of the Yield Gap, so that every region is producing at its maximum yield possible. Hence we can see that all YG scenarios involve less emissions, as food is produced more efficiently in these scenarios. Both number 1 scenarios (CT1 and YG1) include no dietary changes. Number 2 scenarios include 50% reduction in global food waste. Number 3 scenarios include this food waste reduction as well as adoption of a theoretical “healthy diet,” with decreased consumption of sugars, oils, and importantly a huge reduction in red meat and other animal products. In other words, CT1 represents a “business-as-usual” scenario while YG3 represents the optimal path for our food industry, and all other scenarios are combinations of different emission reduction strategies. The two horizontal lines in the graph represent benchmark emissions levels; the dotted black line shows the amount of CO2 produced by agriculture in 2009 and the red line shows the emissions level which would raise global temperatures by 2 ºC, a commonly used target.

The difference between CT1 and CT3 is clearly larger than that between CT1 and YG1. CT3 involves the adoption of dietary changes from CT1, whereas YG1 only involves improved yields from CT1. The larger emission reduction in CT3 means that food-demand changes can actually reduce emissions more than food-supply changes, at least as estimated by the model used here. Once again we can understand the importance of reducing consumption of animal products, as evidenced by the most recent scientific study.

Another 2014 study focused on the present consumption of animal products in UK rather than projecting into the future. In this study, Scarborough et al. surveyed more than 50,000 meat-eaters, fish-eaters, vegetarians, and vegans and calculated the GHG emissions of each of these diets based on “food frequency questionnaires” as well as existing estimates of the GHG emissions of 289 individual foods. Their findings were straightforward and telling: “after adjustment for sex and age, an average 2,000 [Calorie] high meat diet had 2.5 times as many GHG emissions than an average 2,000 [Calorie] vegan diet.” In this case, a “high meat diet” describes one which involves more than 100 grams of meat per day. 100 grams is about 3.5 oz, which is not a very large portion. Thus many meat eaters likely fall into this category.

Not surprisingly given what we know about animal agriculture, these studies clearly had similar findings about the relative emissions of different scenarios, namely the following: In order to reduce the contribution of agriculture to climate change, we absolutely need to eat less animal products. It should be noted that each study used different models, different assumptions, and different scenarios so that quantitative results varied widely. However, this doesn’t weaken the findings because different outputs can be expected from different methods. The relative differences between scenarios and the conclusions drawn by the researchers based on these differences were all remarkably similar, and this is the important part.

All these studies focused on determining the GHG emission reduction possibilities of dietary change, but they did not touch on how this drastic, widespread dietary change can actually come about. People in developing countries who grow their own food or spend much of their income on food likely rely so heavily on animal products in their diet that it would be impossible to eliminate them. They simply do not have other options available. However, many of us in developed countries are able to reduce our consumption of animal products to some degree. We generally spend less of our income on food and have many alternatives to animal-based protein available to us. We are some of the very few people in the world who have this opportunity to make this change, so I believe that it is our responsibility to do so. There is widespread scientific consensus (as evidenced in the numerous studies cited here) that reducing consumption of animal products is a positive step for the future health of our planet and climate. Those of us who understand the reality of climate change and are able to take actions against it should do so.

Studies mentioned in this post, and others:
Importance of Food Demand Management for Climate Mitigation (in Nature Climate Change, August 2014)

The Importance of Reduced Meat and Dairy Consumption for Meeting Stringent Climate Change Targets (in Climatic Change,  March 2014)

Climate Benefits of Changing Diet (in Climatic Change, February 2009)

Food Consumption, Diet Shifts, and Associated Non-CO2 Greenhouse Gases from Agricultural Production (in Global Environmental Change, August 2010)

Dietary Greenhouse Gas Emissions of Meat-eaters Fish-eaters, Vegetarians, and Vegans in the UK (in Climatic Change, June 2014)

Global Diets Link Environmental Sustainability and Human Health (in Nature, November 2014) 

Also, a Civil Eats article on the above study^

Thanks for reading,

Feel free to contact me with any questions or comments at eatfortheearth@gmail.com and check out my twitter, @Eat4theEarth, for interesting links and articles.


How Can We Bring Real Change to Our Food System? Three Ideas

I try to write on here about the big issues and controversies, and after all that information, there is always the same question to ask: what can we do about it? So in this post I’ll give some of my ideas, which upon first look may seem a bit vague or open-ended but only because everyone must take these thoughts in their own personal directions. As I am constantly saying, there is no one easy answer to all the problems with our food system. So here are my thoughts on what we can do to reclaim this industry. It is after all our food system.

1. Choose a diet that reflects your personal beliefs about what defines sustainable agriculture. I won’t tell you to go vegan or to buy only grass-fed beef or to eat all the animal products you want. I won’t tell you to avoid GMOs or to support the technology. I will write about my own opinions but in the end, these are your beliefs and your choices. All I’m saying is that it’s important to apply your beliefs to your every-day life. Maybe you want to take a weekly trip to the farmers market or start a garden to grow your own food. Maybe you want to avoid factory-farmed animal products or anything with palm oil in it. But it is important to realize that our diet is defined by what we do eat and what we don’t eat.

We have to support the products and producers we trust and avoid the ones that we don’t. If we each start to eat based on what we know and believe, the food system will slowly start to change to reflect our choices. As big and powerful as they seem in comparison to us, these big food companies must adjust to what the consumers want. And it is easy to find real examples of this change. When Wal-Mart decided to source its milk entirely from cows not treated with bovine growth hormone, the decision was based on consumer demand. When organic farming grew from nothing to a 30 billion dollar industry, it was because of the individual choices of consumers. (See the figure below.) Clearly, we have real power in our hands.

Graph from the USDA

Check out this video to hear what farmer Joel Salatin has to say about changing our food system for the better. Though Salatin speaks specifically about eating locally grown food, his message about active participation applies to any     dietary or lifestyle choices. I agree with Salatin that in some ways the current problems with our food system are caused by a “crisis in participation.” But we are the participants and this is our crisis to fix.

2. Constantly share, learn, and listen to others’ perspectives. In looking for new thoughts and ideas on the big issues, we will find the information necessary to inform our actions and choices. When we start to think deeply about how our dietary choices affect the environment, we will then encounter new ideas and perspectives. It’s an awesome, self-reinforcing cycle.

Five years ago I didn’t understand why anyone would be vegetarian. I didn’t want to listen to the opinions of any vegan. After a gradual change in perspective, I now choose not to eat any factory-farmed animal products. I try to think of my current beliefs as only a step along a path. And I know that sounds cheesy but it’s one of my strongest beliefs. We can’t just say “Okay I learned that x is bad so I’m not going to eat x any more and that’s it. Now I’m done learning and have done all I can.” We are never done learning. We have to question everything until we understand it fully. It easy to look for a quick fix, but that may mean a simplification of the issues and a misunderstanding of the whole truth.

When we can sit down and have an honest discussion with others while both teaching and learning, we will all become better informed. We will become more aware, more educated, and in turn more motivated to enact change.

3. For some issues that may seem out of reach, contribute to organizations you believe in. As powerful as our every day choices are, they can’t cover everything. For whatever reason, it may be impossible to support a certain organization with our every-day purchases. I remember doing a research project to try to answer the question: how can US consumers support sustainable agriculture and land use in Indonesia? Indonesia is an incredibly biodiverse, fertile, and agriculturally important country: the US imports many of its crops (namely palm oil) that make their way into our food. Still, our consumer choices here can’t completely fix their food system. So how can we help? After doing some research, I discovered Seal Your Cup, a division of Rainforest Alliance which helps small farmers grow crops in a way that is more sustainable for the farmers and the land. You can also support the cause by buying coffee or chocolate labelled with the Rainforest Alliance seal (below). Of course donations still help if you can’t find those products at the store.

In order for a product to bear this seal, it must be sourced from a farm whose practices are approved by the Sustainable Agriculture Network.

While reading about the potentially sustainable use of GMOs in developing countries, I learned about AGRA . This foundation that is financed by Bill Gates works to educate, connect, and provide materials (like high-yield seeds) to farmers in different African countries. Like Seal Your Cup, the NGO essentially brings power and leverage away from distributers to the farmers themselves. If you’re looking for an organization that’s closer to home, maybe you want to check out FarmAid. If you want to support the humane treatment of farm animals, you could give to an organization like Compassion Over Killing. Whatever the cause, someone out there is working hard to do the things we wish we could if we had the time and commitment. They definitely deserve our support and appreciate whatever we can give.


PS: I know that in this post I have provided very little detail as to the specific work of these organizations (and I should definitely do some more research myself). For that reason, I strongly encourage you to research tons of organizations more deeply before deciding who you want to support.