Updated: Feb 7
Environmental concerns, animal welfare, and personal nutrition are the primary reasons someone may adopt a plant based or vegan diet. If you’re interested in plant-based eating, or have already adopted a plant-based diet, chances are you’re somewhat aware there is an environmental impact to going meatless. What you may be more unfamiliar with is the magnitude of impact a predominantly plant diet has on the food system and associated greenhouse gas emissions.
A Call to Action
As climate change worsens, with extreme weather events and natural disasters becoming more severe and frequent, it can be overwhelming to exist in a world that feels like it is burning to the ground or flooding around you. It can be especially challenging when the reaction from world leaders has been unsuccessful in matching the severity of the scientific reality of global warming. Living through ‘a code red for humanity,’ as the Sixth Assessment Report from the United Nations Intergovernmental Panel on Climate Change (IPCC) has been recognized as, has led to a rise in eco-anxiety and eco-grief, especially among the youth (1,2). It’s no wonder that a 2020 national survey found that 41 percent of Americans say they feel helpless, and 22 percent report feeling depressed about global warming (3).
With feelings of despair, anxiety, and helplessness also comes action to alleviate those feelings. While it’s true that widespread governmental and policy change are necessary to combat global warming, it’s also true that individual actions are capable of making real change; individual change accomplished by the masses has the capability to implement larger, institutional change. Because about 25 percent of global greenhouse gas emissions are attributed to the food system, shifting to a plant-based diet is an individual action that can create meaningful change (4,5,6). The shift toward plant foods can be seen in the increased prevalence and sales of plant-based alternatives in the market. In 2017, sales of plant-based food grew 8.1 percent and exceeded $3.1 billion, and this trend is expected to continue (7).
With food trends favoring plant-based meat and dairy alternatives, and with more and more people saying ‘no thanks’ to meat and dairy, you may be curious about the plant-based movement and whether or not the food on your plate truly impacts global warming. Are you ready? Let’s dive in.
Greenhouse Gases and the Food System
While carbon dioxide is the most prevalent greenhouse gas, accounting for about 76 percent of total emissions in the United States, methane, nitrous oxide, and fluorinated gases also contribute to emissions (8). Agriculture is responsible for carbon dioxide, methane, and nitrous oxide emissions (8). While many sectors contribute to carbon dioxide emissions, the agriculture sector is unique in its methane and nitrous oxide emissions. Of specific focus for animal agriculture is methane.
Overall greenhouse gas emissions from food make up about 25 percent of total global emissions (4,5,6). Greenhouse gas emissions from the food and agriculture sector have many sources including livestock and fisheries, crop production, land use, and supply chain. The largest contributors to a food’s total emissions is land use and farming practices (5). Land use includes deforestation and changes in carbon composition of soil from land clearing (5). Farming practices include fertilizer usage and methane emissions from ruminant animals and manure management (5). Supply chain, which includes transportation and packaging of food, contributes a relatively small amount to overall emissions (5). Transportation makes up only six percent of the total food emissions, illustrating what you eat is makes a larger impact on emissions than where it’s from (5).
Farming practices, such as manure and pasture management and use of fertilizers contribute largely to the overall emissions impact of a particular food. Methane is a significant concern because it is more efficient at trapping heat in the atmosphere than carbon dioxide and has shown to be 25 times more potent over a 100-year period (8). In the United States, the agriculture sector is the largest source of methane (8). Methane is naturally produced from ruminant livestock, such as cattle, sheep, and goats, through intestinal fermentation (5,8). Additionally, the management of manure contributes to methane production (8).
Agriculture is also the largest contributor of nitrous oxide emissions in the United States, with soil management accounting for about 75 percent of total nitrous oxide emissions (8). Emissions are related to use of fertilizers, cropping practices, management of manure, and burning of agricultural residues (8).
Land Usage and Deforestation
Land usage accounts for 24 percent of overall food emissions (5). As the world’s population has increased, the amount of land necessary to produce enough food to feed the world population has also increased, resulting in increased deforestation and land clearing. As a result, expanded land use for agriculture has greatly contributed to habitat loss and reduced biodiversity, leading to disruption of vital ecosystems (9). Further, deforestation reduces the ability of forests to absorb carbon dioxide, which further exacerbates climate change.
Currently, about half of the world’s habitable land is used for agriculture, and 77 percent of that land is used for livestock (9). The large percentage attributed to livestock accounts for land used for grazing, as well as the land used for growing crops to feed the livestock (9). Even though livestock takes up most of the world’s agricultural land, it only produces 18 percent of the world’s calories (9).
The amount of land required for production of food is highly variable based on the food, with meat requiring significant more amounts of land than crops for human consumption (5). There is also large variance in land usage between the type of meat, with lamb and beef having the highest land usage at 369.81 m² of land/kg of lamb and 326.21 m² of land/kg of beef (5). Comparatively, poultry requires 12.22 m² of land/kg (5). However, when comparing meat with non-meat food products, it’s clear that land usage for plants is much lower overall. For instance, tofu only requires 3.52 m² land/kg and potatoes 0.88 m² of land/kg (5). Further, it’s been shown that land used for livestock produces twice the emissions (16 percent) as land used for crops for human consumption (8 percent) (5). This illustrates the positive impact of choosing plant foods over animal foods.
Comparisons of Footprints of Food
To compare the associated emissions for specific foods, kilograms of carbon dioxide equivalents are used in order to include emissions from carbon dioxide, methane, and nitrous oxide. Emissions are measured at all levels of the food system from land use to packaging. When comparing data from 38,000 commercial farms and 119 countries, gathered from a meta-analysis of global food systems, it’s easy to see that most of the top emissions producing foods are meat and all of the lowest emissions producing foods are plants (5,6).
The top 10 largest emission producing foods (all units in kg CO2-equivalents per kg of product) (5):
• Beef (for beef) – 60
• Lamb/mutton – 24
• Cheese – 21
• Beef (for dairy) – 21
• Chocolate – 19
• Coffee – 17
• Shrimp (farmed) – 12
• Palm oil – 8
• Pig meat – 7
• Poultry meat – 6
Alternatively, the foods with the 10 lowest emissions (all units in kg CO2-equivalents per kg of product) (5):
• Nuts – 0.3
• Citrus fruits – 0.3
• Apples – 0.4
• Root vegetables – 0.4
• Bananas – 0.7
• Peas – 0.9
• Soy milk – 0.9
• Casava – 1.0
• Corn – 1.0
• Tomatoes – 1.4