Impacts of human activities on the natural world including use of scarce resources (water, land) and release of waste products (greenhouse gases, air pollution).
Adoption of vegetarian and vegan diet patterns is sometimes motivated by a desire to protect the natural environment from degradation through human activities. Raising livestock for human consumption is resource-intensive and is a major cause of several environmental concerns.
- Although farmed animals don't drink much water directly, it takes a very large amount of water to grow plants that are used to feed animals. When analyzing water footprint, "green water" refers to rainfall and other replenishable sources, whereas "blue water" refers to groundwater and aquifers that are drawn down and may not be replenished within our lifetime. When water is scarce, it may be difficult to produce sufficient food for humans if most of the food potential is wasted by feeding it to animals.
- Land is a limited resource that can be allocated in various ways. Currently livestock (or livestock feed) occupy 1/3 of the Earth's ice-free land. If demand for meat continues to grow, then more land will need to be allocated to livestock. Land can only be converted, not produced, and agricultural land often starts as forested area. This results in deforestation. In the worse case, damaged land may undergo desertification making it no longer useful for any human activity and effectively reducing the land available for humans to live on.
- The use of fertilizer to grow crops as feed for farmed animals depends on the Haber process as a source of nitrogen. The production of most chemical fertilizer depends on combustion of methane gas, a fossil fuel that is increasingly linked with "fracking".
- Animal agriculture is a major contributor to greenhouse gas emissions. In particular, the documentary film Cowspiracy (2014) identified intensive cattle farming as one of the world's largest emitters of methane gas and nitrous oxide. Methane gas (CH₄) and nitrous oxide are both very potent greenhouse gases, although they are relatively short-lived in the atmosphere compared to carbon dioxide.
- The kind of intensive farming used to grow feed for farmed animals is a major contributor to ocean dead zones because excessive nutrients, especially nitrogen, drain off the land into rivers and oceans and support the growth of organisms which deplete oxygen content in the water.
- Intensive farming of animals (often referred to as factory farming) describes situations where animals are removed from land and typically confined in buildings. These arrangements concentrate large amounts of fecal waste (excrement/poop) into a small area. Instead of being reabsorbed into the land by natural processes, the solid and liquid waste becomes a pollutant that sometimes washes into waterways.
When asking or answering questions about animal agriculture and the environment, it is important to keep geographic context in mind. For example, the greenhouse gas emissions from animal agriculture are often compared to emissions from vehicles for personal transportation. Greenhouse gas emissions may be dominant in a country with a lot of cars, whereas animal agriculture emissions might be dominant in a region with very few cars.
When considering a geographical context that is smaller than the whole planet, it's also important to consider the impact of borders and trade. For example, a country which raises animals but imports most of its feed will have different results than a country which grows most of its own feed.
Environment vs. Wildlife
Sometimes discussions about environment and sustainability include concerns about impacts on wildlife such as bears, elephants, and fish. The traditional view of environmentalism is closely linked with animal conservation. A conservationist wants to protect animal wildlife in order to preserve that wildlife for the use and enjoyment of future generations. A conservationist perspective includes animals as part of the environment to be protected and managed.
In contrast, an animal rights perspective does not include wildlife as part of the inanimate environment. An animal rights perspective recognizes the sentience of animals and how they can benefit from a well-managed environment, just as humans can. An animal rights perspective does not consider bears, elephants, or fish as resources to be managed, but as fellow inhabitants of the world in which we all live.