The Environmental Impact of Food
Terrestrial food production has been (and continues to be) the largest driver of habitat and biodiversity loss on the planet. Agriculture is responsible for about a third of all greenhouse gas (GHG) emissions—contributing more to climate change than global electricity and heat production. How does the environmental impact of seafood compare?
Greenhouse Gas Emissions
Humans, by way of GHG emissions, are causing several global environmental disruptions. GHGs in the atmosphere trap heat, causing global temperatures to rise. The increased heat causes higher sea levels, more droughts and heat waves, abnormal rainfall patterns, and more intense storms—all of which threaten human well-being around the globe.
Generally, proteins are the most carbon-intensive nutrient our bodies require. Below is a graphic from the World Resources Institute comparing the amount of carbon-equivalent GHG emitted per gram of protein.
Beef, lamb, and goat are the most brutal to the planet because they are ruminant animals—they rely on specialized bacteria in their gut to break down food. These bacteria release a large amount of methane, a potent GHG that strongly contributes to global warming.
The impacts of other complete, animal proteins are mostly related to how much food is needed to raise and care for the animal. For example, chickens are more efficient than turkeys at turning feed into flesh and thus have a marginally lower climate impact. Animal feed needs to be grown, harvested, processed, and shipped to farms—all contributing to emissions. Wild-caught fish feed and grow on their own, thus they have the lowest emissions among animal proteins. Commercial fishing emissions mostly come from boat fuel burned to go fish, so the carbon impact of seafood depends on the species being caught. For example, shrimp and lobster have higher carbon emissions because boats have to constantly stop and start to place/collect traps. Salmon have much lower emissions as they are easy to harvest and found relatively close to shore.
Emissions from plant-based proteins are directly related to their protein density. Food needs to be harvested, packaged, and shipped—all incurring GHG costs—meaning denser foods provide more protein for the weight. There is more protein in a pound of fish than in a pound of nuts, thus GHG emissions per gram of fish protein is lower, seen in the chart above.
A prominent 2014 study in Climatic Change (open access) took a more holistic approach to dietary GHG emissions by examining the daily emissions of different kinds of diets. Researchers categorized people into groups: high, medium, and low meat-eaters; fish-eaters; vegetarians; and vegans. The results are mostly what would be expected: eating more meat produces more emissions. However, fish-eaters (who consumed no other meat) have nearly the same emissions profile of strict vegetarians, differing by about 1%. Vegans are the least impactful eaters.
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Most people in the U.S. and other developed countries are high meat-eaters, consuming over 1.5lbs per week. One high meat-eater replacing that meat with fish would save the emissions equivalent of about 6,000 miles driven over the course of a year.
Space & Water
Eating wild-caught fish has two other key advantages over land-based food: space and water. Terrestrial agriculture and livestock production use over 50% of the world’s arable land and accounts for over 90% of freshwater use. With world population projected to reach over 9 billion by 2050, the increased demand for food will further stretch our land and freshwater resources.
Agriculture is responsible for the clearing of millions of hectares of forests & grasslands; the diversion, contamination, and scarcity of freshwater rivers and lakes; and the extinction of countless species around the world. At the same time, world hunger is at an all-time low and more people than ever have access to a healthy life provided by food. Conserving wilderness is a delicate balance between food needs and preservation.
Yet the amount of space we protect from agriculture is largely dependent on what kind of food we eat—not every kind of food has the same environmental footprint. For example, just 4 agricultural commodities, beef, soy, palm oil, and wood products, are responsible for nearly all rainforest destruction. Land-based meat, specifically meat from ruminants, plays a hugely disproportionate role in deforestation since most of the world’s soy is produced as feed for livestock. Demand for beef and other red meat is, by far, the largest driver of deforestation around the world.
With food production increasing, it may be strange to think that the availability of freshwater is at an all-time low. Water is more essential than anything else, yet people have less of it than ever. Some is diverted to dams for electricity, but most of the world’s water supply is used for growing crops and livestock. Hundreds of millions of people do not have easy access to potable drinking water. Water pollution—much of which comes from agricultural runoff like pesticides and fertilizer, plays a large role.
Seafood has a much lower impact on space and freshwater than land-based food.
In addition to being one of the most carbon-efficient foods on the planet, wild-caught fish require no land, no freshwater, and has a much lower impact on wildlife—no marine fish has ever gone extinct due to fishing. Farmed seafood has similar impacts as land-based food, but is highly dependent on the kind of seafood being cultivated. Farmed sea vegetables (e.g. kelp) and farmed bivalves, like oysters, mussels, and clams are extremely good for the environment. They are typically grown right offshore (requiring little to no boat fuel), require no freshwater, can be grown vertically using very little ocean space, and actually take carbon out of the environment as they grow. Farmed sea veggies and bivalves are probably the best commercially available food to eat for the planet, regardless of plant or animal or macronutrient profile.
Life-cycle assessments and scientific comparisons of foods
A standardized and scientific way to compare the impacts of different foods is with life-cycle assessments (LCAs). LCAs are a modern kind of data that can quantify nearly every environmental impact of a food product throughout all stages of the product’s history. For example, this partial figure from Hilborn et al. 2018 compares the GHG emissions, energy use, air pollution (noted as acid), and water pollution (noted as eutrophication) of 3 sources of animal protein: livestock (yellow), aquaculture (red), and wild-caught fisheries (blue).
You can see that wild-caught fisheries have the lowest impact in every category. Aquaculture is highly species-dependent; farmed shellfish is probably the least impactful thing to eat on the planet, but farmed catfish is one of the most impactful—comparable to beef. LCAs are the best way to directly compare the impacts of different kinds of food products. Last year Poore and Nemecek 2018 published a big database of food LCAs for large-scale comparisons across terrestrial foods; a few weeks later Hilborn et al. 2018 followed up with an in-depth comparison of animal proteins, including several kinds of wild-caught fish and aquaculture species. We went more in-depth on both papers and their findings on our blog—see our coverage at the bottom of this post.
The above chart from World Resources Institute does a great job summarizing the environmental costs of our food (though wild-caught fish are excluded from the figure). Essentially, eating more seafood in place of other animal-based foods is better for the planet. But not all seafood is equal—with so many varieties, there are many factors that determine how sustainable a particular kind of seafood from a particular location is. In the next section of Seafood 101, we explain the aspects of fishing, science, and management that determine sustainability.
Should you feel guilty about your dietary impact?
Almost every ingredient in your last meal was grown on a piece of land that was once wildlife habitat—over half of all arable land on the planet has been cleared for agriculture or livestock. Is this something to feel guilty about? No—trading wilderness for human health and nutrition is a moral decision made by our early ancestors to build civilization—you played no role in developing our global food system. Though shifting your diet away from beef is one of the best and easiest individual actions you can take to improve the planet, meaningful, large-scale improvements and conservation action will come with policy change and political pressure. Beef eaters voting for pro-environmental politicians & policies will do more for the Earth than food-conscious non-voters. You can register to vote (in the U.S) here.
This post is part of Sustainable Seafood 101.
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