Thursday, December 17, 2015

Environmental impacts of food: vegetarian isn't quite as "nice" as you thought

Everybody knows that producing beef is harder on the environment than vegetables and fruits—and like a lot of stuff everybody knows, that may be wrong.

(Image: Iceberg lettuce--maybe not the environmental good guy you thought. Credit: USDA ARS.)

Which is not to whitewash the impact of livestock production, but neither to overstate its impacts. More on livestock at the end of this article, but one message is that well-managed, local, grass-fed beef operations that aren’t contributing to new forest loss may have significantly lower impacts than the global averages.

A team of researchers has recalculated impacts of various food choices, and found that a lot of vegetable products have significant climate and other environmental impacts—often more than some meat products.

The article is “Energy use, blue water footprint, and greenhouse gas emissions for current food consumption patterns and dietary recommendations in the US.” It is published in the journal, Environment Systems and Decisions by authors Michelle S. Tom, Paul S. Fischbeck and
Chris T. Hendrickson, all from Carnegie Mellon University.

In the Science Daily article on the paper, co-author Fischbeck makes you feel a little less self-righteous about that salad. 

"Eating lettuce is over three times worse in greenhouse gas emissions than eating bacon, Lots of common vegetables require more resources per calorie than you would think. Eggplant, celery and cucumbers look particularly bad when compared to pork or chicken," he said.

(The folks at ClimateProgress insist that calories aren't a fair way to look at this, and that if you consider lettuce and bacon by weight, bacon is six times worse. You can read their take here. )

The paper notes that the subject is complex. If you give up a half-pound burger, you need far more than a half pound of lettuce and kale to make up the same number of calories.

On a per-calorie basis, fruits and fruit juices have the worst results of any food when it comes to energy use and water use. That’s largely because they have such low calorie counts. And their water cost is high in part because a lot of U.S. fruit is grown in California drylands that require a heck of a lot of irrigation. Fruits are, however, comparatively low in greenhouse gas emissions on a per-calorie basis.

Red meat products are far lower in energy and water, but have very high greenhouse gas emissions numbers. Poultry looks pretty good on all counts. Seafood, not so much. It has high energy and greenhouse gas calculations, largely from the amount of energy that fishing fleets use to catch either wild fish, or the fish products used to feed farmed fish.

Grains, nuts, sugars, fats and oils look better, on a per-calorie basis, than vegetables

Which is not to say that you should always follow environmental numbers when deciding what to eat. That might be an unhealthy path, said lead author Tom

"There's a complex relationship between diet and the environment. What is good for us health-wise isn't always what's best for the environment. That's important for public officials to know and for them to be cognizant of these tradeoffs as they develop or continue to develop dietary guidelines in the future," she said.

The authors looked at three diet scenarios: “(1) reducing Caloric intake levels to achieve ‘‘normal’’ weight without shifting food mix, (2) shifting food mix to food patterns recommended by the USDA Dietary Guidelines, without reducing Caloric intake, and (3) reducing Caloric intake levels and shifting food mix to meet USDA Dietary Guidelines in order to achieve and maintain healthy weight.”

The USDA may provide a better health scenario, but it may not be the best environmental diet, the authors write: "Shifting from current consumption patterns to USDA dietary recommendations corresponds to an increase in diet-related energy use, blue water footprint, and GHG (greenhouse gas) emissions among American adults."

If you’re like many Americans, and you eat and weigh too much, there’s good news. Cut your caloric intake and you’ll cut your impact on the planet.

On the other hand, if you go to the USDA’s recommended diet, don’t feel smug.

“GHG emissions increase despite reduction in calories and a shift to the USDA recommended food mix, which lowers red meat consumption. Although meat products have the highest emissions per calorie, overall GHG emissions increase due to increased caloric intake of dairy, seafood, fruits, and vegetables, which collectively offset emission reductions resulting from decreased meat consumption as well as reduced sugars, fats, and oils,” the paper says.

The authors recognize that their data involves broad averages based on wide-scale food data. Water use has less impact if it is in an area without a shortage of water. Locally grown food can have distinctly better numbers than stuff that’s shipped long distances.

And the livestock picture is complex. While greenhouse gas emissions are high, livestock farming can be critical to the survival of farmers in poor parts of the world. 

The Food and Agriculture Organization (FAO) of the United Nations notes that,“It provides livelihoods to about 1.3 billion people ... For many poor farmers in developing countries livestock are also a source of renewable energy ... and an essential source of organic fertilizer for their crops.”

 The FAO says the situation isn’t black and white, and notes that there are ways to significantly reduce the environmental impact of cattle and other livestock:

“Land degradation – controlling access and removing obstacles to mobility on common pastures. Use of soil conservation methods and silvopastoralism, together with controlled livestock exclusion from sensitive areas; payment schemes for environmental services in livestock-based land use to help reduce and reverse land degradation.

“Atmosphere and climate – increasing the efficiency of livestock production and feed crop agriculture. Improving animals’ diets to reduce enteric fermentation and consequent methane emissions, and setting up biogas plant initiatives to recycle manure.

“Water – improving the efficiency of irrigation systems. Introducing full-cost pricing for water together with taxes to discourage large-scale livestock concentration close to cities.”

These New Zealand ranchers make the point that when you include the greenhouse gas cost of growing the feed, grass-fed cattle produce lots less greenhouse gas than feedlot cattle. 

© Jan TenBruggencate 2015

No comments: