Eating and Drinking We make choices about food more often than about any other climate change driver. It therefore makes sense to begin our climate diet with our actual diet. Though it is a complicated business assigning an overall number to the carbon footprint of food, most regulators and scientists place it within the top five sources of emissions, nationally. These emissions happen directly through the operation of farm equipment, the methane burps of cows, and the transportation of product to market, and also indirectly through the replacement of powerful carbon-sequestering wild systems like forests and grasslands with CO2-leaking monocultures like corn and wheat. Even the earth beneath our feet is diminished by present methods of agriculture. The global soil stock, the world''s second largest carbon storehouse after the ocean, has lost somewhere between 50 and 70 percent of its original carbon dioxide to the atmosphere because of overtilling, overfertilization, excessive pesticide application, and other practices commonly deployed in the modern food system. There are other important reasons to focus on fixing your food footprint. Biodiversity, water use, and exploitation of open space-key metrics in how scientists assess sustainability-are all profoundly impacted by how we grow our food.

The central issue of this book, though, is greenhouse gas emissions, so I''ve organized this chapter around which food changes would have the largest impact on that metric. With apologies to the animal liberation movement (which I support), the approach here is not specifically vegan or vegetarian but rather what some call "climatarian"-an emphasis on the most realistic food changes that could be taken up by the largest number of people to lop the greatest possible chunk off American emissions. Here, then, is a baker''s dozen of changes you can make that will lighten your emissions load in the kitchen. 1 Ease up on meat and cheese. A switch to a plant-based diet shaves at least a ton of CO2 per year off your carbon footprint. But even just eating fewer pounds of animal products can be highly impactful. Beef can cost the planet more than 27 kilograms of CO2 emissions per kilogram of meat. The emissions cost of producing beef is consistently high regardless of how cattle are raised.

Both ham and cheese are also emissions-intense-each of them comes in at more than 11 kilograms of CO2 per kilogram of food. Some might fret that eating fewer animal products would cause a protein deficit. Untrue. Americans actually overeat protein by about 30 percent. In spite of what fad diets might tell you, the USDA recommends only about 90 grams per day for men and 60 grams for women-less than one McDonald''s small hamburger. And unlike carbohydrates or fats, excess protein can''t be stored in the body-we literally piss it away. 2 Consider the chicken. Once you''ve reduced your overall intake of animal products, choose the kinds of protein you do eat with emissions in mind.

At less than 7 kilograms of CO2 per kilogram of meat, chicken ranks as the most emissions-efficient widely produced terrestrial animal protein. True, it''s no lentil-it takes a minuscule .9 kilograms of CO2 for a kilogram of that little brown bean to come to market. But if every beef-eating American switched to chicken, the United States would cut its carbon emissions by over 200 million tons. 3 Or the fish. Wild fish can be even more carbon efficient than chicken. An average of all American wild-caught finfish comes in at 1.6 kilograms of emissions per kilogram of edible fish flesh.

That''s because wild fish don''t require feed or husbandry to reach harvestable size. Nature takes care of that. The primary emissions cost of wild fish is the burden of catching them and transporting them to market. But not all wild fish are good emissions bargains. The word fish comprises thousands of species caught in dozens of different ways. Fishing methods that entail long journeys into distant waters with repeated stops to haul gear burn a lot of diesel. So, for instance, longline-caught tuna and swordfish sit near the top of the fisheries emissions list. Dragging heavy gear over the seafloor is also carbon-expensive, making flounder, cod, and other "bottom-trawled" species less desirable choices.

Conversely, seafood that is caught in midwater trawls and purse seines-nets that don''t touch the bottom-tend to be carbon lightest. Alaska pollock (the fish most commonly found in your Filet-O-Fish), and small pelagic fish like mackerel, sardines, herring, squid, and anchovies, all fall into this carbon-light category. Farmed fish, meanwhile, tend to float around in an emissions space somewhere between chicken and pork. 4 Make oysters your appetizer instead of shrimp. All those shrimp cocktails add up: out of the 15 pounds of fish and shellfish Americans eat each year, more than 4 pounds are shrimp, making shrimp by far the most popular seafood in the United States. But shrimp, particularly farmed shrimp, are notably terrible from an emissions point of view-by some estimates as bad as beef. That''s in part because over the last few decades, shrimp farming has destroyed millions of acres of one of the world''s most powerful carbon-sequestering ecosystems: mangrove forests. Mangroves, on average, store more than twice the CO2 per acre as tropical rain forests but are often cleared to make way for coastal shrimp ponds.

All this makes a shrimp cocktail an extremely carbon-intensive appetizer. Oysters, meanwhile, carry none of these costs. In fact, farmed bivalves-oysters, clams, and mussels-are extremely carbon-light. They require no feed, subsisting on a diet of wild algae and filtering and cleaning the water as they grow fat. That clever trick puts some bivalves in the same carbon cost range as many vegetables. Mussels, the grand emissions champions of the animal kingdom (and also one of the most affordable seafoo ds out there), can cost just .6 kilograms of carbon and other greenhouse gasses per kilogram of mussel meat. Take that, lentil! 5 Be a picky plant eater.

It''s undeniable that a good vegan diet can do more to cut a person''s greenhouse gas emissions budget than any other kind of eating pattern. But as the environmental physicist Gidon Eshel puts it, "You can be a perfectly terrible citizen of the world and be vegan, or you can be a perfectly upstanding citizen of the world while eating animals. Both are possible." There are three main reasons for this. The first is the aforementioned point about protein. Overeating the protein component while on a vegan diet can unnecessarily add emissions pounds to what would otherwise be a green way of eating. The second problem can be food processing. Taking apart plant-based nutrients and reassembling them in such a way that makes them resemble animal products takes energy.

True, the new wave of hyper-processed meat replacements (Beyond and Impossible burgers, for example) have about half the carbon footprint of chicken. But they are still about five times more emissions-intense than a simple bean patty. The third reason some plant-based diets can be problematic brings us to our next rule. 6 Be thoughtful with local. The food movement of the last twenty years has stressed the importance of sourcing food from local producers, and we''ve seen a tremendous proliferation of farmers'' markets as a result. Buying locally does keep family farms working and saves land from real estate development, which can in and of itself be good for emissions reductions. But local farming can be carbon intensive. In an effort to meet supermarket-style everything-always demand, some small-scale farmers have adopted practices to grow crops that don''t naturally prosper where their farms happen to be located.

Take a wintertime salad. Growing greens in cold months in the Northeast requires heated greenhouses and other carbon-intensive practices. It is therefore much more carbon-efficient to get those same winter greens from California, where higher ambient temperatures and economies of scale mean that the overall carbon inputs are much lower, even when you include transport cost (about 10 percent of most food''s carbon burden). If you still want to eat Northeastern greens in the Northeast in cold months, think about something that''s regionally and seasonally appropriate, like cabbage. Be thoughtful and strategic when you drive to the farmers'' market as well. Emissions-wise, a 20-mile round trip to buy a single head of broccoli is notably wasteful. 7 Roots rule. In case you''re wondering which foods deliver the absolute most nutrients for the absolute least emissions, the answer according to the most recent comparative analyses is .

carrots. Sorry not to be more exciting, but roots like carrots and parsnips carry with them a strikingly low emissions cost. The second best performer in terms of nutrients delivered per unit of carbon dioxide emitted is . sorry, again, not so exciting: small pelagic wild fish like anchovies. Little fish also rule. 8 Avoid flying food. By flying food, I mean airfreighted food. While a more hospitable, distant climate can offset the carbon cost of transporting food when the transport mode is ship or rail, airfreighting is so emissions-expensive that it blows away any other consideration.

Overall, air-freighting food is fifty times more carbon costly than the least carbon intensive, transporting by ship. Flying foods are typically highly perishable products brought to us at great speed to avoid spoilage. Since fuel efficiency declines the faster you go, this is a decidedly wasteful practice. One study in the UK found that while only 1.5 percent of fruit and vegetables in that country are carried b.